Title: Sweet potatoes in Florida
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Permanent Link: http://ufdc.ufl.edu/UF00026374/00001
 Material Information
Title: Sweet potatoes in Florida
Alternate Title: Bulletin 34 ; Florida Agricultural Extension Service
Physical Description: Book
Language: English
Creator: Spencer, A. P.
Publisher: Agricultural Extension Division, University of Florida
Publication Date: June, 1922
Copyright Date: 1922
 Record Information
Bibliographic ID: UF00026374
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aab7775 - LTQF
amt6433 - LTUF
47285716 - OCLC
002570126 - AlephBibNum


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The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida

Bulletin 34

(Acts of May 8 and June 30, 1914)





The total production of sweet potatoes in the United States
for the year 1921 was estimated at 98,660,000 bushels. The
southern states are gradually increasing their shipments. In

Fig. 1.-Sweet potatoes piled for the round bank

fact, most of the net gain in sweet potato shipments of this
country for the season of 1921-22 came from the southern

June, 1922

Florida Cooperative Extension

states, which section produces the moist flesh type of potato.
This fact indicates that this popular southern potato is gradu-
ually gaining favor in the northern markets.
The sweet potato crop of Florida should be one of its major
crops, particularly in the former cotton growing area where the
soil is so well adapted to growing it. Many of the difficulties
that have arisen in storing and shipping sweet potatoes have
been overcome. These facts are sufficient to warrant consicer-
ably more emphasis being placed on the growing of sweet pota-
toes than has been heretofore.


A sandy loam soil with a clay subsoil is well adapted to the
growing of sweet potatoes. The crop, however, can be grown
under a variety of soil conditions with a fair degree of success.
This is true particularly in Florida, due to this state's light
soils and warm climate.
Of all the types of soil, rolling pine land is usually selected be-
cause of its suitability to the crop and the ease with which it
can be tilled. With sufficient drainage, proper culture and a fair
amount of organic matter in the soil, a good yield of potatoes
may be expected from such soil, if moisture conditions are held
fairly uniform thruout the season.
Sandy flatwoods lands also produce good crops. Where drain-
age is provided and the plants set on beds, a satisfactory yield
may be expected, if other conditions are favorable. However,
special provision for drainage is essential for most flatwoods
Rolling hammock lands with compact subsoils are used very
generally for growing sweet potatoes, and, with a fair amount
of humus, a satisfactory crop may be expected from such soil.
But if these hammock lands are not well drained-are too heavy
or contain considerable muck-they are not as suitable as the
pine lands.
A fair amount of organic matter is essential, without which
the soils dry out during dry periods, in addition to requiring
much more fertilizer. Where vegetation can be turned under
each year, it results in the same beneficial effects for sweet
potatoes as for other farm crops.
Muck soils tend to produce a heavy growth of vines and un-

Bulletin 34, Sweet Potatoes in Florida

even sizes of tubers, and in some cases no tubers at all. In
some cases tubers become abnormally large and almost worth-
less for table use. However, as muck lands become compact
and well drained, particularly if they contain some sand, fairly
good crops may be expected.
Very thin sandy lands usually produce sweet potatoes of a
good quality, but too often the yield is low. Such soil, being so
thin, is lacking in organic matter and, consequently, has not the
power to retain moisture. In most cases it is not profitable to
grow sweet potatoes on such land, unless it is improved by
turning under vegetation and fertilizing heavily.
Sweet potatoes can be grown successfully on new land, par-
ticularly when planted as a mid-summer crop. They do not
produce best when planted early in the spring. The soil must
have the proper dampness and warmth, if success is sought.
Without a fairly constant supply of moisture, potatoes are likely
to be long and stringy and unfit for market.


Like any other root crop the sweet potato requires good cul-
tivation as long as it is possible to get between the rows. As

Fig. 2.-Siding up the beds with a specially constructed implement (Photo
by Bureau of Markets and Crop Estimates, U. S. D. A.)

Florida Cooperative Extension

the plant is grown on beds in Florida, surface cultivation re-
quires special implements, especially after the vines begin to
It is important that the land be prepared thoroly far enough
in advance of setting that a good moisture supply may be in-
sured. Where potatoes are to be planted early in spring, the
land should be plowed early in January, in order that it may
settle and capillary attraction be established between the soil
and the subsoil before the dry months. During dry weather,
if plowed immediately before the plants are set, the soil will
become very dry and many plants will die. It will be difficult
to make those that live grow off rapidly, which is necessary
for good yields. The plowing should be broadcast and from
six to eight inches deep, depending on the soil. If no crop is
to precede the sweet potatoes, it is well to keep the surface of
the soil harrowed in order to make it firm and moist.
Usually it is not advisable to rebreak the land before plant-
ing. Simply make the beds, apply the fertilizer and set the
plants. Where early preparation is not provided, the soil is
likely to dry out, which will result in a poor stand, a slow
growth of the vines, and most commonly a low yield of pota-
toes that are mainly culls and unfit for market.
A good supply of humus in the soil is important for supply-
ing plant food, as well as for retaining moisture. Therefore,
on the average pine lands where leguminous crops, grasses or
other vegetation can be turned under and rotted before plant-
ing time, the soil will be much improved and the plants will
get a greater amount of fertility from the commercial ferti-
lizer applied. In addition the soil will retain much more moist-
ure, making doubly sure the prospects for a good yield.


The time of planting will have a decided effect on the yield.
The yields from very early plantings are usually lighter than
those from plantings made just previous to the season of sum-
mer rains. This is due principally to a warmer soil and a more
constant supply of moisture during summer. When plants are
set in early spring, unless irrigation is supplied, they are likely
to suffer from lack of moisture; and, as sweet potatoes require

Bulletin 34, Sweet Potatoes in Florida

warm soil, the temperature of the soil in early spring is not
quite high enough to induce the most rapid growth.
To have an early summer crop, it is necessary to set plants
late in March or early in April; but where a maximum yield
is desired and no special preparations are in mind for market-
ing early, it seems best to set the plants in May or June. Slips
should be used for setting up to June 1, after which vines
should be used.
The season of planting, however, must be determined to some
extent by the dampness of the soil. It is unwise to set out
plants when the soil is very dry, unless an irrigation system
has been provided. Many of the plants will die, likely, before
they start to sprout, and those that live will grow off slowly,
become spindling and produce a poor yield.
Under favorable conditions planting can continue up to Au-
gust 1, but usually this is too late for heaviest yields. Plants
set as late as this are likely to make a vigorous growth while
young, when the soil is very moist, but will yield poorly, if
there should be a lack of rainfall in September or before the
plants have set any tubers. Had such potatoes been started
well in advance of the rainy season, allowed to establish a good
root system and to make a substantial growth by September,
rainfall and temperature variations would affect them less than
if planted later.
For the main crop it is seldom advisable to plant before May
15, for, if planted earlier and not harvested until late fall,
many tubers are likely to be over-sized and cracked, and unfit
for market purposes. Therefore, a good time to set sweet
potato plants is between May 15 and July 10, ordinarily. An
exception to this is when the rainy season is prolonged thru

Experiments conducted at the Florida Experiment Station
and published in Bulletin 156 of that station show that sweet
potatoes make the heaviest yields on average lands when a com-
plete fertilizer is used. These experiments were conducted for
five successive years on sandy pine land of average fertility.
In each case where any one of the three essential elements;
namely, ammonia, phosphate and potash; were omitted the yield
was notably less than where these elements were applied.

Florida Cooperative Extension

The plots receiving no ammonia produced an average of ap-
proximately 37 bushels to the acre less than the plots receiving
The plots receiving no phosphate produced an average of 52.2
bushels to the acre less than where the phosphate was applied.
The plots receiving no potash produced 121.9 bushels to the
acre less than the plots that received potash.
These experiments, therefore, indicate the advisability of a
complete fertilizer and, in particular, the importance of the
potash element.
Two forms of ammonia were used, sulphate of ammonia and
dried blood. Dried blood gave an increase of 5.6 bushels to the
acre over sulphate of ammonia.
Acid phosphate was the only form of phosphate used.
Two forms of potash, sulphate and muriate of potash, were
used. The plots fertilized with muriate of potash yielded an
average of 18.2 bushels to the acre more than the plots fer-
tilized with sulphate of potash, thus showing the superiority of
Plots that received an application of 2000 pounds of ground
limestone to the acre produced approximately the same yields
as where no lime was used. This indicates that lime is of little
or no value for sweet potatoes on the average Florida land.
Fertilizer Application.-To produce maximum yields on aver-
age pine land, apply from 600 to 1500 pounds of fertilizer to the
acre. The actual amount needed is determined by soil condi-
On light poor soil it is seldom profitable to apply more than
600 pounds of fertilizer to the acre. A larger amount may in-
crease the yield, but not sufficiently to pay for the extra ex-
Conditions determining the amount of fertilizer that can be
used profitably depend on the kind of soil, its natural fertility,
the character of its subsoil, the humus it contains, and its gen-
eral physical condition. Usually where the soil is in a high
state of cultivation and has more than the average natural
fertility, large amounts of fertilizer may be used profitably.
But where the soil is loose and open, lacks humus and fertility

Bulletin 34, Sweet Potatoes in Florida

and is apt to be affected by unusual rains or continued drought,
large amounts of fertilizer are seldom profitable. No definite
amounts or formulas can be recommended for giving best re-
sults. However, the above suggestions can be used as a guide.
Where the soil is unusually fertile, containing large amounts
of humus and organic matter, as does muck soil, the amount
of ammonia may be reduced to one-half or one-third. The
phosphate and potash also may be reduced but the potash
should be decreased in the same proportion as the ammonia.
These soils are unusually rich in ammonia but do not have an
excess of either phosphate or potash.
Analysis.-A sweet potato fertilizer analysis should show ap-
proximately the following: 4 percent ammonia, 6 percent phos-
phoric acid and 6 percent potash. This formula may be pur-
chased in mixed goods or made from the following materials:
Sulphate of ammonia..................25 percent 320 pounds
Acid phosphate.........................-- 16 percent 750 pounds
Muriate or sulphate of potash..48 percent 252 pounds
Inert matter (filler) .....-.......... 678 pounds

Total, 2000 pounds (1 ton)
If the goods are home mixed, there is no occasion to add the
filler material.
In case it is desired to apply a fertilizer from the above mate-
rials at the rate of 100 pounds to the acre, mix together the fol-
lowing materials:
Sulphate of ammonia------....------...........................25 percent 16 pounds
Acid phosphate----...............--........-------16 percent 38 pounds
Muriate or sulphate of potash....................48 percent 13 pounds
This gives a total application of 67 pounds to the acre, but it is
equivalent to 100 pounds to the acre of 4-6-6 fertilizer. The
amount of each material needed for making up any given
amount can be calculated from these figures. To illustrate-
if you wish to apply 900 pounds to the acre, multiply by 9 the
amount stated for 100 pounds. Do this for each of the mate-
rials used.
When to Fertilize.-If the fertilizer is applied early in spring,
one application two weeks before the plants are set is recom-
mended. If, however, the fertilizer is applied for summer plant-
ing, the amount used should be divided into two applications.

Florida Cooperative Extension

The first application should be applied two weeks before the
plants are set, and the second after the plants have been set one
Stable Manure, if available, can be used to advantage at the
rate of two to five tons to the acre. Apply manure and ferti-
lizer to the soil in about the following manner: After the
ground has been prepared and is ready for planting, open up fur-
rows four feet apart and distribute the manure into them. Then
cover this manure with two furrows, one on either side. This
forms a shallow bed. Apply commercial fertilizer on these half-
made beds and work it into the soil by running a one-horse fer-
tilizer distributer over the top of the beds. Allow the beds to

Fig. 3.-On fertile soils, or well-fertilized, sweet potatoes grow luxuriantly
in Florida

remain in this condition for about two weeks, until about ready
to plant. Then finish preparing the beds by plowing furrows
on either side, making it as high as necessary. Set the plants
in these beds.
Where no stable manure is used the opening of this furrow
is unnecessary. Plow up the shallow beds and proceed with
the commercial fertilizer, the first application of which should
be in the ground two weeks before the plants are set, lest it
injure the newly set plants. The second application should be
made about thirty days after the plants are set. This will

Bulletin 34, Sweet Potatoes in Florida

make it necessary to apply it in the sides of the beds. Work
it in with a cultivator. This will tend to pull down the beds,
but they can be thrown up later with a plow.
Sweet Potatoes on "Cowpenned" Land.-The penning of cattle
on land to be planted to sweet potatoes usually gives good results
because of the manure and tramping the land gets. It, at least,
emphasizes the importance of using manure for sweet potatoes.
Vegetation in the Soil.-The importance of adding vegetable
matter to the average sweet potato soil of Florida cannot be over-
estimated. All vegetation should be plowed under soon enough
to decay well by planting time. A leguminous crop is partic-
ularly beneficial for sweet potatoes where it can be turned under
before the crop is planted.
Results from the use of added fertilizing matter are best when
the soil has a good supply of organic matter. Because it im-
proves moisture conditions in the soil during the life of the crop,
it is advisable to incorporate into the soil as much of such mate-
rial as is possible.

Fig. 4.-A plant bed properly laid off and boarded up, and of convenient

Florida Cooperative Extension


As sweet potatoes are propagated from plants, provision
must be made for growing an ample supply of plants. In
Florida they can usually be grown early enough, when set in
the open. However, if it is desired to set plants in the field
on or before April 1, the plant beds will need some protection
and artificial heat, especially in Middle, North and West Florida.
In South Florida, if covered with pine straw or some similar
material, they will be protected against freezing.
For a plant bed one should select a protected spot, preferably
on the south side of a windbreak, where the plants will get all
the sunlight possible. The sweet potato does best in a warm
soil with a relatively high temperature. The location should be
well drained and the soil should be fairly fertile.

A plant bed may be either in a shallow excavation or on a
level, either of which should be about five feet wide and of the
necessary length. The bed should not be so wide that it is in-
convenient to pull the plants without stepping on the beds. In-
close in a frame made of eight-inch boards, as shown in figure 4.
In the bottom of the bed should be placed from four to six
inches of fresh horse stable manure. On top of the manure

Fig. 5.-Healthy, strong, vigorous plants (Photo by Bureau of Markets
and Crop Estimates, U. S. D. A.)

Bulletin 34, Sweet Potatoes in Florida

place a layer of soil three inches thick. Then spread the seed
potatoes over this layer of soil. On the potatoes lay down a strip
of two-inch-mesh poultry wire, over which place one and a half
inches of loam soil. (The chicken wire holds the potatoes in
place when plants are being drawn from the bed.) When the
plants begin showing thru the ground, add an additional layer
of soil in which the roots may develop properly. To insure long
stocky shoots, there should be six inches of soil over the pota-
toes at pulling time. After the potatoes are planted the soil
must be kept moist by sprinkling. However, too much water is
detrimental as the temperature of the bed will be kept down.
Add just enough moisture to promote good growth. The bed
needs comparatively little attention until the draws are big
enough to transplant.
A slip five inches long is ready to be transplanted. After each
crop of draws is pulled, keep the soil moist and in ten days or
two weeks another crop will be ready to take off.
In estimating the amount of seed potatoes necessary to grow
draws for a given acreage, it is estimated that one bushel will
produce 8,000 to 10,000 plants for the early crop, or enough for
a tenth of an acre. Ten bushels should be planted for each acre
of early planting. If, however, the seedbed is planted early and
the slips are allowed to grow into vines, three bushels will pro-
duce enough vines to set an acre, if conditions are favorable.
When this is done the slips should be transplanted to where they
will have ample room to grow and make vines.

A slight application of a 5-5-5 commercial fertilizer should be
broadcasted on the plant bed about the time the sprouts are ap-
pearing above the soil. Work into the soil by means of a light
rake or hoe. (A 5-5-5 fertilizer is one that has 5 percent of
ammonia, 5 percent of phosphoric acid and 5 percent of potash.)
This added plant food will stimulate and hasten the growth of
the plants.
It is also advisable to provide canvas or cheesecloth for the
protection of the beds. This material can be stretched over
the bed at night and removed during the day. It prevents radia-
tion of heat from the bed, and thus keeps it warm. Plants re-
quire a temperature of 700 to 800 F. to grow well. There will

In estimating the amount of seed potatoes necessary to grow
draws for a given acreage, it is estimated that one bushel will
produce 800 to 1,000 plants for the early crop, or enough for
a tenth of an acre. Ten bushels should be planted for each acre
of early planting. If, however, the seedbed is planted early and
the slips allowed to grow into vines, three bushels will pro-
duce enough vines to set an acre, if conditions are favorable.
When this is done the slips should be transplanted to where they
will have ample room to grow and make vines.

Florida Cooperative Extension

be little difficulty in holding it above 50 F., if the foregoing
precautions are taken.
Where the plants are needed for late planting only, forcing
methods will not be necessary, as late plantings will produce all
the plants needed.

Nothing is gained by transplanting potato draws before they
are sufficiently strong, since to do so checks their growth. When
the plants are pulled from the bed, it is best to set them out im-
mediately. However, if they are to be shipped, allow them to
wilt in the shade for at least six hours before packing. This
tends to harden them and to reduce the number dying. Immedi-
ately following a rain is a good time to set out potatoes. If the
area to be planted is small, the plants can be transplanted at
almost any time and watered.
Number of Slips to Plant an Acre.-It requires about 8,000
slips to plant an acre of potatoes with four-foot rows, when
the plants are set 15 inches apart in the row. The width and

Fig. 6.-Draws, or slips, crated to be shipped (Photo by Bureau of Mar-
kets and Crop Estimates, U. S. D. A.)

Bulletin 34, Sweet Potatoes in Florida

distance for planting depends on the richness of the soil and the
variety of the potatoes. In soil that is rich the plants can be
set closer than in poor soil;
Sand with varieties that pro-
Sduce many vines the rows
should be a little wider than
With varieties that produce
but few light vines. The rows
should be wide enough to per-
mit cultivation for five or six
v weeks after the plants are
Asset, particularly if set in early
'- spring when the weather is
r likely to be dry. If planted
in mid-summer when rains
are frequent, cultivation to
S ~-- conserve moisture is not nec-
: !- Slips Compared with Vines.
-There is no difference in
A \ setting the vines and in set-
Fig. 7.-Proper root development and ting the slips. However, as the
top for transplanting (Photo by Bu- vines usually are set later in
reau of Markets and Crop Esti- the season and are larger and
mates, U. S. D. A.) stronger, they can be set un-
der less favorable conditions
than can slips. This is due largely to the superior strength of the
vine and its ability to withstand unfavorable conditions.
In setting the vines, first cut them into 15-inch lengths, insert
the butt end at least 6 to 8 inches deep. The soil should be left
firm around the vine in order to prevent the bed from drying
Vines are preferred to slips, where it is practical to grow them,
since the vines are usually stronger and mature their crop quick-
er than do slips. This is due to the vigor of the vine cuttings.
It is further true that many more vine cuttings than slips can
be secured from a bushel of seed. For early planting one must
depend on slips, but for late planting it will not be difficult to
secure ample vine cuttings from a much smaller amount of seed,
especially if the slips are transplanted into rows for the purpose
of growing vines.

Florida Cooperative Extension

There are about four commercial varieties of sweet potatoes
recommended for Florida. Several others are grown locally but
do not seem to have any particular merit and, consequently, little
commercial importance.
The most important commercial varieties are Porto Rico,
Triumph, Nancy Hall and Big Stem Jersey. The Red Providence
and Norton Yam are grown commercially but are of less import-
ance. Other varieties such as Dooley Yam, Pumpkin Yam, Nig-
ger Killer, "Pattysaw" and Red Buck, are grown in gardens
but are not recommended for commercial plantings.
The Porto Rico is the most popular variety thruout Florida,
on account of its rich color, moist soft flesh, and its rich, sweet
and juicy flavor. It is also very popular in the markets of other
southern states, and, in fact,
wherever a moist-fleshed po-
tato is demanded. It yields
on the average a good crop of
marketable potatoes, which
can be stored several months
and kept in good condition,
if harvested without being
It produces heavy, purple
vines, the leaves being large
and thick and greenish brown
in color with purple markings

Fig 8.--The Porto Rico, famous in the South for its richness of flavor and
rare delicacy

Bulletin 34, Sweet Potatoes in Florida

on the veins, around the edge of the leaf and on the petiole
The Nancy Hall is less popular for home use and for most
southern markets than is the Porto Rico. The tuber is light
yellow in color with flesh of a creamy-pink yellow. When cooked
the flesh is moist, soft and sweet, but not as rich in appearance
as the Porto Rico.
It is an average yielder on
light soils and has proven a
satisfactory variety to grow
under average conditions. Of
moist potatoes it is one of the
most satisfactory for north-
ern markets. It has the disad-
vantage of a tendency to
crack, if grown on rich soil
or if allowed to remain in the
soil for some time after ma-
turing. The vines are in-
clined to be bushy. The leaves
are mottled greenish yellow
with purple markings at the
junction of the blade and

Fig. 9.-The Nancy Hall cooks soft, moist and sweet and is popular on
the northern markets

The Triumph is recommended for early planting, particularly
when the crop is to be shipped to northern markets. It is drier
than the Porto Rico or Nancy Hall and for that reason is less
liable to bruising and is a better shipper.

Florida Cooperative Extension

Being propagated from slips, there is little difficulty in pro-
ducing early potatoes of this variety. And for spring shipments
to northern markets it is one
of the most dependable. Since .
it is a comparatively dry po-
tato, it is not very popular
on southern markets. How-
ever, where the quality is
good it is comparatively free
from stringiness and when i
ripe is fairly sweet. The vines
make a heavy growth and the
leaves are deep green with
purple stems and veins. Both
the peel and the flesh of the
roots are light yellow in color.

Fig. 10.-The Triumph is a good shipper

The Big Stem Jersey is a dry mealy potato and sells much
better on northern than on southern markets. It has not been
popular in the South because of its dryness. In the North it
is well known as being dry and mealy. It can be handled easily
without bruising.
When this potato is planted in Florida it is usually with an
idea of shipping to northern markets. It can be produced and
placed on those markets in July, or earlier than most other va-
rieties. This requires very early planting. When grown early
in spring, particularly if the soil is dry, the yield is often light.

Bulletin 34, Sweet Potatoes in Florida

For that reason it has not
been grown to any extent ex-
cept by a few who have made
special preparation to grow it
at this season. It is doubtful
if it ever will be a satisfactory
variety for home use or local
The vines are rather scant,
long and creeping, and the
leaves are small and green in
color. The roots are dark
yellow and their flesh creamy
yellow in color. When cooked
it is dry and mealy.

Fig. 11-The Big Stem Jersey, a good shipper and popular in the North
because of its dryness and mealiness

The Norton Yam is a good variety for local markets and for
home consumption. It is a sweet, moist potato but is inclined
to be stringy, if its growth is retarded by dry weather. The
roots are russet yellow in color, and their flesh white, flaked
with yellow. The leaves and stems are rich green and the vines
light green in color. The vines are inclined to have a long strag-
gling growth.
The Red Providence is grown commercially and for home use.
It is usually a good yielder and is propagated easily. In color
the roots are tan, shading into yellow. The flesh has a tinge of
pink. The potato is comparatively free from stringiness. It is
moist and a good keeper, if harvested without bruising. The
vines are green with purple markings at the nodes, and the leaves

Florida Cooperative Extension

have purple stems which
shade into green. The vines
make a medium heavy
The Pumpkin Yam is best
suited for local consumption.
It is a very juicy potato and
bruises easily, unless handled
carefully. As to color, the
roots are salmon with a rich
yellow flesh. When cooked it
is sweet and juicy. The leaves
are long and irregular, with
prominent yellow veins.
The Nigger Killer, "Patty-
saw" and Red Buck are of
little importance from any
standpoint. They seem able

Fig. 12.-The Norton Yam, both
for home use and to supply lo-
cal markets. It is a sweet, moist
potato. However, it does not do
well when the weather is dry

to produce light inferior crops under neglected conditions. They
are moist and comparatively sweet, but are not recommended
for commercial plantings.


The practice of selecting seed has been neglected very greatly
in much of the sweet potato growing area. Little along this line
has been done in Florida, with the result that the average yield

Bulletin 34, Sweet Potatoes in Florida

is low. In fact it is difficult to
secure a high yield of uni-
form, marketable potatoes.
While the lack of good seed is
not altogether responsible for
this condition, it is an im-
portant factor.
The planting of sweet po-
tato vines from volunteer
plants is partly responsible
for many low yields. These
volunteer vines come up from
potatoes which were over-
looked when harvesting the

Fig. 13.-The all-round Red Providence
previous year's crop. Usually such potatoes are small and in-
ferior. One cannot expect plants from such seed to give the
best returns, nor to produce roots uniform in color and shape
and true to variety.
The practice of bedding the inferior or cull potatoes for seed
is also responsible for low yields. While there are many small
roots suitable for seed, the probability of getting low-yielding
plants from them is so great that it is better to feed them to
livestock and to purchase seed, if necessary, even at a much
greater expense.
Sweet potato seed should be selected for uniformity of type,
color and variety, and should be free from disease. Careful seed
selection year after year results in the ultimate production of
a higher percentage of marketable potatoes. Such potatoes can
be graded and packed so as to compare favorably with the best
that reach the eastern markets, and also make a decided im-

Florida Cooperative Extension

provement in the general appearance of the potatoes on our
southern markets.
There are several diseases of sweet potatoes that mar their
appearance and increase the number of seconds and culls. By
the proper selecting of seed when the potatoes are dug, the
proper storing of seed potatoes, the careful re-sorting, the throw-
ing out of all diseased tubers, and the disinfecting of seed the
amount of diseased potatoes will be reduced, their yield increased
and their quality improved.
As many diseases are carried into the field by planting dis-
eased seed, it is advisable to treat all seed immediately before
bedding. This is done by placing the potatoes in a solution made
of 1 ounce of corrosive sublimate mercuricc chloride) and 8
gallons of water, and letting them remain for ten minutes. Then
bed immediately. In case the soil is generally infected, this
treatment is of little service. In such a case plant some other
Much care is needed when harvesting sweet potatoes to avoid
bruises. Southern potatoes,
because of their high content
of water, are bruised more
easily than the drier varieties.
et The diseases of sweet potatoes
can do comparatively little
damage, unless the potatoes are
bruised or broken. If the crop
is to be stored for several
months, too much care cannot
be exercised to prevent bruis-
ing. If comparatively free of
diseases and if carefully hand-
led to prevent bruises, breaks
and cuts, practically all pota-
toes will cure well and few will
rot. However, if they are
Fig. 14.-This hamper looks like hauled loose in the ordinary
it was shipped by parcel post,
but it was by express (Photo by wagon body, handled careless-
Bureau of Markets and Crop ly from the wagon to the cur-
Estimates, U. S. D. A.)

Bulletin 34, Sweet Potatoes in Florida

ing house by forks or shovels, the blemished and rotted will
amount to as high as 75 percent or more of the original bulk.

Sweet potatoes are packed in hampers, baskets, crates and
barrels. The kind of package used is determined largely by
how the potatoes are shipped. For car-lot shipments the hamper
has the advantage of being packed easily in the car. For ex-
press shipments this package is objectionable in that it is more
easily broken than the bushel basket or crate.


Fig. 15.-B-sk"et: are cirvenient containers (Photo by Bureau of Markets
and Crop Estimates, U. S. D. A.)
If sweet potatoes are placed in storage houses, the bushel crate
is preferred, sice crates of this type may be filled with pota-
toes immediately. from the field and stacked up in such a way as
to provide veni '-ttion. This last crate, therefore, minimizes
handling and by rising. If the potatoes are carefully sorted in
the field, they can be placed in these crates immediately; but
usually they must be re-sorted just before being shipped in or-

Fig. 16.-Crates minimize handling and bruising (Photo by Bureau of
Markets and Crop Estimates, U. S. D. A.)

Florida Cooperative Extension

der to remove the blemished or unmarketable. The tight bar-
rel is used generally when shipping direct from the fields to the
market. This barrel is not headed as is the Irish potato barrel,
the potatoes being held in by a covering of burlap fastened down
with a hoop. Such a package would not be suitable for storing
in a storage house because good ventilation cannot be secured.
Packages filled and ready for marketing should contain pota-
toes uniform in color, size and quality. The packages should
be well filled so that they will be held firm in the pack and thus
prevented from settling down and being bruised in transit.
Never ship sweet potatoes in sacks for long distances. This
is impossible to do without practically every tuber's becoming
bruised. Like any other product, a neat-appearing package us-
ually finds a ready sale at a good price, and, therefore, care
must be exercised in placing sweet potatoes on the market that
they may sell for the best price.

Sweet potatoes to be stored in houses or banks for two or
more months must be comparatively free of bruises and blem-
ishes and well-matured, or many will decay and others grade

Fig. 17.-Barrels are generally used when shipping direct from field to
market (Photo by Bureau of Markets and Crop Estimates, U. S. D. A.)

Bulletin 34, Sweet Potatoes in Florida

low. Before being piled together, broken and bruised ones
should be sorted out for immediate use.
Rotting in storage is caused by a fungus that develops slowly
when the potatoes are spread out thin and have a free cir-
culation of air over them. When they are piled together and
have but a limited circulation of air, there is usually some in-
crease in temperature and moisture in the air about them, which
makes conditions favorable for the action of the fungus. This
accounts for the fact that potatoes stored in small beds keep
better than those stored in large beds.
The round bank, as shown in figure 1, has an advantage over
the larger bank in that the pile is small and there are more po-
tatoes exposed to a free circulation of air. If the bank contains
15 bushels or less, it will hardly be necessary to place a venti-
lator in the center of it. However, the top should have a venti-
lator so that, if there is any heating, the warm air can escape.
After the potatoes are shaped up they should be covered with
about four inches of straw, and over this a thin layer of dirt in
order to keep out cold and rain.
When a larger quantity of potatoes are to be stored, the bank
can be long and narrow. But on account of the larger pile there
will be more heating, consequently more ventilation will be
needed. The ventilated bank, as shown in figure 18, provides a
free circulation of air from one end to the other.
Invert a V-shaped trough and lay it in the bottom of the bed.
Under this place supports to hold the trough two inches off the
ground. Pile the potatoes over this ventilator.

Fig. 18.-A ventilated sweet potato bank, designed and used by T. K.
Godbey, Waldo, Florida

Florida Cooperative Extension

Such a bank can be made five or six feet wide at the bottom
and about four feet high and can have any desired length up to
20 feet. Such a bed 20 feet long will hold about 200 bushels.
When the beds are shaped up and ready to be closed in they
should have a light layer of straw, held down and protected by
a layer of boards, the upper ends of which rest on a ridge pole.
The boards should overlap sufficiently to keep out rain. No straw
should be placed in the bottom of the bed. The potatoes will
keep better, if laid on the ground.
A layer of dirt can be placed over the boards. This will be
needed during frosty weather. The potatoes will keep much
better, if a fairly uniform temperature is maintained both day
and night. To provide such a temperature, a thicker wall than
provided by the boards and straw will be necessary. In unus-
ually cold weather both ends of the ventilator in the bottom of
the bed can be covered with dirt.
Ample ventilation is necessary to keep sweet potatoes sound
and fresh after being stored. If fresh air can enter from the
bottom, circulate thru the potatoes and escape at the top of
the bank, the potatoes will keep with comparatively little shrink-
ing or rotting. And if a uniformly cool temperature is main-
tained, there will be little sprouting.
Sweet Potato Curing Houses are in general use in many sweet
potato sections. Where a large acreage is grown for several
years in succession, a curing house is recommended. Such a
house is not recommended unless there are 1500 bushels or more
to be stored. In small houses it is not easy for the temperature
to be held uniform. When the outside temperature is frequently
70 F., or higher, it is often difficult to prevent sprouting. This
can be controlled in a large house better than in a small one.
Also, for a crop of 1500 bushels or less, the initial cost and neces-
sary supervision will be too large to justify a storage house.
Therefore, if the crop is small, it is more profitable either to
market the potatoes at harvesting time or to store them in a
A storage house with a capacity of from 5,000 to 10,000
bushels can be operated at a relatively low cost. A small house
requires practically the same supervision that a large one does.
In either case an attendant must watch and hold the tempera-
ture and moisture in the house at their proper places.

Bulletin 34, Sweet Potatoes in Florida

Digging and Handling.-Potatoes to be cured in a storage
house should be left in the ground until well matured. If frost
destroys the vines, the potatoes should be dug at once or have
their vines cut off at the level of the ground. If the dead rotting
vines remain attached to the tubers, germs of decay will enter
the tubers and they will decay in storage. After the potatoes
are dug they should be placed in the storage house just as soon
as they are dry. If the weather is clear and relatively cool,
allow to dry before storing; but, if the weather is hot, do not
let them remain exposed to the sun, since to do so will cause
them to sunburn. It is usually best to house the potatoes as
they are dug, allowing them to remain on the ground just long
enough to dry.
In digging potatoes care should be taken not to bruise them
by throwing from one row to another or into a loose wagon bed
or into bags. Sort and put into a basket or box, load onto the
wagon and haul them directly to the storage house. If stored
in crates, there is no occasion to handle more than once. If the
grading is done in the field and the different grades are kept
separate, handling at the cars will be facilitated.
Houses can be built with or without bins. Those without bins
require that the potatoes be stored in crates. This is economical
and usually most practical, as it saves handling the potatoes
after they reach the storage house, and the boxes can be piled
up in such a way that air can circulate freely thru them.
Curing the Potatoes.-As soon as the potatoes are stored ex-
cess moisture in the house should be driven off by means of a
stove or heating flue. For the first ten days the temperature
in the house should be from 80 to 850 F. with ample ventila-
tion. The temperature maintained will depend on weather con-
ditions. Ventilation is needed to drive off the excess moisture
and to keep the potatoes fairly dry. During the day the win-
dows and doors may be opened but at night they should be
After ten days the temperature within the curing house should
be gradually reduced to 550, where it is kept as near as pos-
sible as long as the potatoes are in the house. In case the
temperature falls to 450 or lower, a fire should be started again
and the temperature raised to 55. If the house becomes moist
at any time during the curing period, it will be necessary to
dry it out.

26 Florida Cooperative Extension

A storage house can be heated with an ordinary sheet-iron
stove. The more uniform the temperature can be held the bet-
ter the potatoes will keep. For this reason coal is preferred to
wood for heating purposes. In commercial storage houses with
a capacity of 10,000 bushels or more, a large heating system is
advisable. The important points in the control of heat in a
storage house is to bring in fresh air, to drive out all moisture-
laden or foul air and to keep the temperature within the house
to 55. In Florida it is difficult to hold the temperature down
to 550, particularly in the fall months when the outside tem-
perature is from 70 to 80'. It is important, therefore, in the
construction of the house to be sure that ventilators are placed
properly and that air spaces are in the walls so that a uniform
temperature may be maintained and not constantly varied.
Advantages of the Sweet Potato Storage House are as follows:
First, the sweet potatoes can be kept in a marketable condi-
tion until prices are satisfactory, even for several months after
Second, the potatoes can be placed on the market in good con-
dition with a minimum loss from decay.
Third, sweet potatoes that are stored properly can be shipped
to distant markets several months after being harvested.

Fig. 19.-Crated sweet potatoes on the way to market (Photo by Bureau
of Markets and Crop Estimates, U. S. D. A.)

Bulletin 34, Sweet Potatoes in Florida

Fourth, the grower is enabled to watch his potatoes while
they are in storage and, should they show a tendency to rot or
sprout, he may be able to dispose of them.
The details for the construction of a sweet potato storage
house are contained in Farmers' Bulletin 970, United States De-
partment of Agriculture, Washington.
In order to market sweet potatoes to best advantage, they
must be properly graded and packed. The general practice of
shipping all the potatoes from a field in loose cars, unsorted,
is wasteful. The seller usually gets only the price of his lowest
grade, the best potatoes being sold for the price of the poorest.
It is always best not to ship cull potatoes. They have little
or no market value, at least not sufficient to cover freight
charges. Such potatoes are worth from 30 cents to 50 cents a
bushel for stock feed or for canning.
Potatoes should be graded according to fixed standards, such
as those worked out by and given in Circular 99 of the Bureau
of Markets and Crop Estimates, United States Department of
Agriculture. These standards, with. slight modifications, are ap-
plicable to most of the southern varieties. Until this is done
southern sweet potatoes will sell for less than they are worth,
and the returns from this valuable crop will continue relatively
low. The standards mentioned above follow:

U. S. Grade No. 1
U. S. Grade No. 1 shall consist of sound sweet potatoes of
similar varietal characteristics which are practically free
from dirt or other foreign matter, frost injury, decay,
bruises, cuts, scars, cracks, and damage caused by heat,
disease, insects (including weevils), or mechanical or other
The diameter of each sweet potato shall not be less than
one and three quarter inches nor more than three and one-
half inches, and the length shall not be less than four inches
nor more than ten inches, but the length may be less than
four inches if the diameter is two and one-quarter inches
or more.
In order to allow for variations incident to commercial
grading and handling, five percent, by weight, of any lot
may not meet the requirements as to diameter and length,
and, in addition, six percent, by weight, may be below the
remaining requirements of the grade.

Florida Cooperative Extension

Any lot in which the diameter is not less than one and
one-half inches and which contains a greater percentage by
weight of sweet potatoes below one and three-q"arters
inches than is permitted in U. S. Grade No. 1, but which
otherwise meets the requirements of such grade shall be
designated as U. S. Grade No. 1 Medium.
Any lot in which the length is not less than six inches nor
more than twelve inches and which contains a greater per-
centage by weight of sweet potatoes above ten inches in
length than is permitted in U. S. Grade No. 1, but which
otherwise meets the requirements of such grade shall be
designated as U. S. Grade No. 1 Long.
U. S. Grade No. 2
U. S. Grade No. 2 shall consist of sound sweet potatoes
of similar varietal characteristics, not meeting the require-
ments of the foregoing grades, which are free from serious
damage caused by dirt or other foreign matter, frost in-
jury, decay, bruises, cuts, scars, cracks, heat, disease, in-
sects, or mechanical or other means, and which are not less
than one and one-half inches nor more than three and one-
half inches in diameter.
In order to allow for variations incident to commercial
grading and handling, five percent by weight of any lot
may not meet the requirements as to diameter, and, in ad-
dition, six percent by weight may be below the remaining
requirements of this grade.
U. S. Jumbo Grade
U. S. Jumbo Grade shall consist of sound sweet potatoes
of similar varietal characteristics, which are free from
serious damage caused by dirt or other foreign matter,
frost injury, decay, bruises, cuts, scars, cracks, heat, dis-
ease, insects, or mechanical or other means, and which are
not less than three and one-half inches in diameter.
In order to allow for variations incident to commercial
grading and handling, five percent by weight of any lot
may be less than the diameter prescribed, and, in addition,
six percent by weight may be below the remaining require-
ments of this grade.
U. S. Grade No. 3
U. S. Grade No. 3 shall consist of sweet potatoes not
meeting the requirements of any of the foregoing grades.
Definition of Grade Terms as Used in These Grades
"Practically free" means that the appearance shall not
be injured to any extent readily apparent upon casual ex-
amination of the lot, and that any damage from the causes
mentioned can be removed without appreciable increase in
waste over that which would occur if the sweet potatoes
were perfect.

Bulletin 34, Sweet Potatoes in Florida

"Diameter" means the greatest dimension at right angles
to any portion of a central line running through the sweet
potato from stem end to root end.
"Free from serious damage" means that any damage
from the causes mentioned can be removed without increase
in waste of more than ten percent by weight over that
which would occur if the sweet potatoes were perfect.

Sweet Potato Silage.-The value of the sweet potato as a sil-
age crop has been determined by the Florida Experiment Sta-
tion and reported in Press Bulletin 274 of that station.
In those experiments potatoes were stored in the silo just
as is corn or sorghum. Or, in other words, the potatoes were
run thru an ensilage cutter at harvesting time and kept in a
concrete silo until the following May. Sweet potato silage, com-
pared with corn silage, shows the following analysis:
Moisture Crude protein Nitrogen free ext. Fat
Sweet potato silage........ 54.8 1.82 39.4 0.66
Corn silage.......................... 72.7 2.1 15.4 .08
During those experiments a test was made with ten cows to
compare the feeding values of sweet potato and sorghum silages
for milk production. Both were fed with a concentrated ration
of wheat bran and cottonseed meal. The test was continued for
43 days with the following results:
The cows fed with sweet potato silage produced 2,641 pounds,
or 307 gallons of milk. During the same period the cows fed
sorghum silage produced 2,416 pounds, or 281 gallons of milk.
This gave a difference of 26 gallons in favor of the sweet potato
The cows in this test were as nearly average cows in every
respect as can be selected from the ordinary herd. The test
serves to indicate that the advisability of making sweet potatoes
into silage can be determined only by their market value.
Sweet Potatoes for Milk Production.-In feeding tests con-
ducted by the Florida Experiment Station for the purpose of
comparing sorghum silage and sweet potato silage for milk pro-
duction, it was found that, when fed with cottonseed meal and
wheat bran, 4,8191/2 pounds of sweet potatoes produced 3,1221/4
pounds of milk at a feed cost of 17 cents a gallon, and that 6,898
pounds of sorghum silage, with the same additional feeds, pro-
duced 2,8001/4 pounds of milk at a cost of 14 cents a gallon. In
making these tests the amount of silage fed was based on the

Florida Cooperative Extension

digestible nutrients in the foods given, so that practically the
same amount of food value was contained in the sweet potatoes
as in the sorghum silage. It was also estimated that the cost
of the sweet potatoes was 30 cents a bushel and that of the
sorghum silage $3 a ton.
For feeding dairy cows the value of sorghum silage may be
estimated at $6 a ton, and sweet potatoes at 60 cents a bushel,
when made into silage. This will give a fair idea of the relative
value of sweet potatoes compared with sorghum silage.
Sweet Potatoes as Hog Feed.-The advisability of feeding
sweet potatoes to hogs is determined also by the market value
of the sweet potatoes. When sweet potatoes are worth more
than 60 cents a bushel, it is seldom profitable to feed them to
hogs. There is, however, in every crop a quantity of broken,
bruised and unmarketable potatoes which can be utilized to good
advantage as hog feed. On account of their high moisture and
relatively low protein and fat content sweet potatoes must be
supplemented with grain, if fed to fattening hogs.
Supplemented with concentrates and pasture, sweet potatoes
are an excellent hog feed. By using approximately half the
grain that would be used with pasture alone, growing shoats
do well on this root crop. Hogs turned into the sweet potato
field after the main crop is harvested gather and eat many small
potatoes and roots that otherwise would be wasted. Or the
potatoes may be gathered and stored and fed as needed to the
hogs in troughs or on a platform. Approximately two pounds
of grain for 100 pounds of live weight of hogs, added to a
ration of sweet potatoes, will produce satisfactory gains.
According to an experiment reported in Florida Experiment
Station Bulletin 90, when the ration is entirely of sweet potatoes
the hogs become unthrifty and actually lose weight after being
fed 42 days.

Bulletin 34, Sweet Potatoes in Florida

Much information in this bulletin was secured from Mr. A. C.
Brown of the Florida State Plant Board.
Several photographs showing plant beds and varieties were
taken in the sweet potato grounds under the control of the State
Plant Board.
Photographs supplied by the Bureau of Plant Industry and
Bureau of Markets and Crop Estimates, United States Depart-
ment of Agriculture, and shown in this bulletin are valuable in
presenting the subject matter herein.

SOIL REQUIREMENTS...................---..------------------ 2
GENERAL CULTURE..................--.... ------------ -------
TIME TO PLANT-.......................----..------- ----- ------------ 4
FERTILIZATION ....................................... -- ------------ 5
GROWING POTATO PLANTS..---..................---- ...-- ...---.-------- .. 10
SETTING POTATO PLANTS...........----...---... ---------- ------------ 12
VARIETIES ..................................... ------------------ ------- 14
SEED SELECTION.........................--------------------------- 18
SEED TREATMENT.............----.....----------------------------- 20
HARVESTING ...................................-- --..- --- ---------.... 20
PACKAGES .................. .....................-- -- ----------- 21
STORING SWEET POTATOES-............----..........--...... ... --.....-...... 22
CURING AND STORING..................-- --...------------------------- 24
MARKETING --....-...........---- --..... ................-- ----------------------- 27
United States Grades for Sweet Potatoes--.....................---------.... --.. 27
SWEET POTATOES AS STOCK FEED............---......------- --- ----------------- 29
ACKNOWLEDGMENT ...--...... -........------------ -------------31

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