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FOR COMMERCIAL GROWERS
Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gaineville.
ONION PRODUCTION GUIDE
PART I BULBING TYPES
Onions can be grown on most of the soil type
found in Florida. Excellent yields can be obtain
with the newer varieties and hybrids. Lack o
suitable climate at harvest time for the proper
curing of the bulbs is a major factor limiting dom-
mercial production of onions in Florida. The
humid spring weather will not generally permit pro
per curing of the onion bulbs. Artificial curing of
the bulbs can be accomplished by using drying
equipment. Generally, under Florida conditions,
onions grown on organic soils do not cure and keep
as well as onions grown on sandy soils. In most
growing situations, raised beds should be used for
best water control.
The varieties described below will grow under the
short daylight conditions of winter and bulb in the
spring with increasing day length. Plant only short
day varieties recommended for the South.
Eclipse.-Highly resistant to the disease pink
root, medium size, thick-flat shaped and white
Excel.-Highly resistant to the disease pink root,
medium size, thick-flat shaped, and amber skinned.
Texas Grano 502.-Large size, top-shaped, and
Ringer.-Similar to Texas Grano 502, but has a
higher percentage of single centers and is slightly
more spindle shaped. Highly resistant to the
disease pink root.
Granex.-Hybrid, highly resistant to the disease
pink root, thick-flat to globe shaped, and yellow
Laredo.-Highly resistant to the disease pink
root, globe shaped and yellow skinned. (For Trial.)
Tropicana.-Resistant to the disease purple
blotch, thick-flat shaped, and red skinned. Pun-
gent. Stores well.
Red Creole C-5.-Resistant to the disease purple
blotch, small, thick-flat shaped and red skinned.
Very pungent. Stores well. (For Trial.)
RANGE OF PRODUCTION DATES
To Field Bed
Sept. 15 Nov. 15 Dec. 15-Jan. 15
1 Onion transplants should be "pencil-size" and vigorously
growing. The tops can be lightly pruned 5 to 7 days
before transplanting to facilitate ease of handling.
2 Onion bulbs continue to "size up" after the tops fall
over late in the season. To help insure uniform curing of
the majority of bulbs, the tops can be "rolled" down
with a light roller when 10% of the tops have fallen
Transplant Production Bed
12-24" between rows
Production Field Beds
12-24" between rows
12-24" between rows
10 to 20 seeds/ft. of
row (about 20/A rate).
2-3# of seed will yield
enough transplants for
1-3" between plants
3-4 lbs. seed per acre
Mineral soils used for the production of trans-
plants should be fertilized with 800 to 1,000
pounds of 8-8-8 per acre. If an organic soil is
utilized, a 0-8-8 material can be substituted. The
fertilizer should be worked into the upper 2 inches
of soil about 10 days before seeding. The soil
should be kept in a moist condition.
The following table indicates the recommended
rates of fertilization for different soil types for use
in the production field.
Fertilizer Rates and Usage
Basic Application Sidedressing Applications
Soils Pounds Actual/Acre Pounds Actual/Acre
N P205 K20 N P205 K20
Irrigated 120 120 120 15 0 30
Non-Irrigated 96 96 96 15 0 30
Peat-Muckl 0 120 120 -2
Marl 54 72 72 15 0 30
1 The amounts of fertilizer suggested here are the amounts
needed for organic soils low in P205 and K20. Where
soil tests show a medium level of P205 in an organic soil,
reduce the suggested amount ot P205 by one-third;
when soil P205 levels are high, reduce by two-thirds.
Follow the same suggestions for medium and high levels
2 The amounts of fertilizer suggested are sufficient to
grow crops under normal conditions. Most crops will
respond to supplemental applications of nitrate nitrogen
during periods of cool weather or following heavy rain-
The basic application of fertilizer may be applied
as a single dose prior to planting or as split applica-
tions with /4 to /2 applied prior to planting and the
remainder in 1 to 3 applications at later times.
Split applications favor a minimal soluble salts
build-up in the root zone and a reduction in the
amount of the basic fertilizer lost from the root
zone due to leaching. Timing and number of split
applications depend upon weather, grower ex-
perience, and grower equipment.
The use of supplemental fertilizer applications
depends upon the weather conditions following
application of the basic fertilizer. Normally, after
heavy leaching rains an application of a sidedressing
material may be needed.
Minor Elements In the absence of previous
history and experience on sandy soils a "shotgun"
approach can be used. A general guide for adequate
minor elements is the addition of 0.3% MnO,
0.2% CuO, 0.3% Fe203, 0.2% ZnO, and 0.2% B203
to the fertilizer mixture. Another good material
containing these same elements is FTE 503 at 20 to
30 pounds per acre.
On muck and peat soils, higher rates are neces-
sary to overcome the tendency of minor elements
to be completed or tied-up by the organic matter
in these soils.
*PRECAUTIONS: Read pesticide labels thor-
oughly before opening container, and observe all
safety precautions. Dispose of empty containers
promptly and safely. Pesticide usage is subject to
changes and cancellations. Keep current on
recommendations and regulations by consulting
county agents, experiment stations, and industry
Insecticides Rates and Use
Insect Material/100 Gal. Dust To Harvest
Thrips1 Diazinon 4E, 1 pt. 10
Malathion 5E, 1/ pt. Malathion 5% 3
Parathion 4E, /2 pt. Parathion 2% 15
Phosdrin 2E, 1 qt. 1
Leaf Miners Diazinon 4E, 1 pt. 10
Parathion 4E, 1 pt. Parathion 2% 15
1 Thrips Apply insecticide when thrips appear, repeat
when necessary. Direct nozzles over rows close to plants.
Addition of spreader-sticker to spray is suggested.
Spraying down into sheaths is very important.
Cutworms.-If cutworms are known to be pre-
sent, a preplant application of 2 pounds active in-
gredient per acre toxaphene or chlordane can
be used. The soil should not be disturbed for 3 to
5 days after application. If cutworms become a
problem after the onions have been planted, a bait
must be used. A 21/2% toxaphene or a 2% chlor-
dane bait at the rate of 20 to 40 pounds per acre
can be used.
Wireworms.-Control can be effected by preplant
soil applications of parathion or diazinon. On
mineral soils, 2 pounds active ingredient per acre of
parathion or diazinon can be used. On muck and
peat soils, apply parathion at 5 pounds or diazinon
at 4 pounds active ingredient per acre. Distribute
the material evenly over the soil surface and incor-
porate immediately into the upper 6 inches of soil.
This should be done 2 to 3 weeks before planting.
Mole Crickets.-If the insects are known to be
present, a preplant spray, dust or granule applica-
tion of the following insecticides can be used about
a week prior to planting: diazinon (2 pounds active
ingredient per acre) or chlordane (4 pounds active
ingredient per acre). A preplant bait (2% chlor-
dane) at the rate of 20 to 40 pounds of bait per
acre can also be used.
After the crop has been planted, control is
limited to the use of a bait at the rate given above.
Onions are severely affected by sting, stubb
root, root-knot, and awl nematodes. Stubby-roo
nematodes frequently build-up rapidly following
fumigation with D-D or Telone and cause injury t
direct seeded onions. Where this nematode occurs
fumigate and plant sets or transplants. Onions ar
sensitive to bromine, so a fumigant which does no
contain bromine should be used.
Nematicides Rates and Use
Rates1,2 Fluid Oz./Chisel
Nematicide Gallons/Acre Per 1000 Linear Feet
Vidden D 20-25 59-73
Telone 15-20 43-59
1 The overall rate per acre of fumigants is based on a
12-inch chisel spacing.
2 For organic (peat and muck) soils, rates should be
Fungicides Rates and Use
Disease Fungicide Lbs./100 Gallons Minimum Days
Downy Mildew zineb 75%
(Peronospora plus sticker 2 71
Purple Blotch maneb 80%
(Alternaria plus sticker 1% NONE
1No time limit on dry onions, 7 days on green onions.
Damping off.-Fungus organisms attack seedlings
at or slightly below the soil line. Seedbed sanita-
tion and good drainage conditions help prevent
occurrence. Seed treatment with such materials as
Arasan is also helpful.
Pink Root.-Fungus organisms attack weak or
injured roots and the roots turn pink and darken
until they die. The fungus organisms live in-
definitely in the soil and can be easily transported
by equipment or transplants. Onions should not
be grown in fields known to be heavily infested
with pink root organisms. The use of tolerant or
resistant varieties can be effective where infesta-
tions are not severe.
Newly emerging seedlings are susceptible to
damage from windblown particles. To prevent a
loss or reduction in stand and the need to reseed or
replant the acreage, windbreaks should be estab-
lished for protection of the seedlings. Where
windbreaks are not utilized for protection, a light
overhead irrigation to wet the soil surface can pre-
vent the sandblasting effect.
Onions are a shallow rooted crop and an ade-
quate supply of moisture is needed to maintain the
plants throughout the growing period. Growth
"checks" due to lack of moisture often can result
in the increased occurrence of doubles or splits
which reduce the overall crop quality. When the
plants begin to mature, irrigation should be re-
duced. Excessive irrigation at this time may induce
a regrowth or sprouting of new roots which can
hinder the proper curing and storage following
Onions are shallow rooted and can be seriously
affected by competition from weeds for soil
moisture and nutrients. Shallow cultivation prac-
tices are recommended. Deep cultivation can cut
and injure roots which results in reduced growth
and reduced yield. When bulbing has begun, culti-
vation should cease. Chemical methods of con-
trolling weeds result in reduced weed competition
and less "trash" to cope with at harvest.
Herbicides Rates and Use
Time of Lbs. Active Ingredient/A
Herbicides Application Sandy Organic
To Crop Soils Soils
CDAA (Randox) Preemerge 4-6 4-6
See Footnote 1. May be
applied as a postemergence
but before weed emergence.
Apply as directed spray to
base of plants at second true
leaf stage. DO NOT USE ON
GREEN BUNCHING ONIONS.
CIPC Preemerge 3-4 6-8
CDAA + CIPC Preemerge 6+6
See footnote 1. DO NOT USE
ON GREEN BUNCHING ONIONS.
DCPA (Dacthal) Preemerge or 10%
DCPA + CIPC Preemerge 5 + 1
Posttransplant (5 + 1) For trial
1 CDAA is more effective against grasses than broadleaf
Bolting.-The production of seed stalks follow-
ing conducive weather conditions is given the name
bolting. The switch from the vegetative to the
reproductive state of growth (bolting) in onions is
induced by exposure to prolonged cold weather.
As a general rule of thumb, bolting is greatest when
onions are exposed to a late warm fall followed by
a cool spring. A cool fall and a mild spring result in
the least amount of bolting. The size of the trans-
plants or sets used, as well as temperature and
variety, influences the amount of bolting that will
occur. Generally, the larger the size of the trans-
plants or sets, the higher the incidence of bolting.
Sprouting.-A chemical treatment of 2 pounds
active ingredient per acre of maleic hydrazide ap-
plied 10 to 14 days before harvest retards high
respiration and sprouting in storage.
Onions must be adequately cured after harvest
to prevent rotting in storage. To facilitate rapid
and uniform curing, the onions may be undercut
and "lifted" in the field. These practices facilitate
the curing process by reducing the water uptake
and growth due to the cutting of the roots. Under-
cutting is usually done 7 to 10 days before harvest.
The harvested onions may be windrowed and
left in the field, weather permitting, to dry or they
may be topped and placed in shallow crates under
roof to dry. Mechanical drying can be done by pas-
sing heated air through the stacked crates allowing
for adequate circulation. The onions can be cured
in 48 hours at temperatures not exceeding 110F
provided there is good circulation of the heated air.
Discard all diseased, injured, and "bottle-necked"
bulbs prior to storage. Store only well cured bulbs
or loss due to rotting will be high. Well cured
bulbs exhibit "tight" necks and dry outer scales.
storage temperature should be 320 F with 65-70%
elative humidity. Most mild onions grown in
orida do not store well and usually cannot be
tored safely for extended periods of time.
PART II GREEN BUNCHING TYPES
Green bunching onions can be grown from "sets"
or seed. Sets are small onion bulbs measuring /2 to
% inch in diameter. When using sets, they should
be sized to get uniform maturity time and size.
Under good growing conditions, the bulbs produce
marketable bunching onions about 45 to 60 days
after planting. Green bunching onions can also be
grown from seed, but to produce a salable onion
by this method requires 75 to 90 days. Sets can be
used for green bunching onions for late fall and
early winter marketing. Seed can be used for later
Not all varieties are available in both sets and
seeds. A good source of sets can often be difficult
to find. When a grower finds a satisfactory source,
it should be maintained. Nearly all the varieties
utilized for bulbing onions can be direct seeded and
used for green bunching onions. However, there
are non-bulbing varieties that have been selected
specifically for green bunching onions that may be
Bulb forming types used prior to bulb formation
for bunching onions
Varieties used most often from sets:
White Portugal or Silverskin
Varieties most often direct seeded
Crystal White Wax
Non-bulbing types, usually produce clumps which
are divided and used as bunching onions
Planting Dates (Sets) Harvesti
s Planting Sets
*If you plant seed, seed in the field at 6 to 8 pounds
Same as for bulbingg" types.
Same as for bulbingg" types except for where noted.
Green bunching onions are perishable so storage
should not be more than several days. The storage
conditions should be 320 F and 90-95% relative
humidity. Exposure to high temperatures will
result in yellowing and decay of the tops.
1. Florida Extension Circular 193, "Commercial
Vegetable,Insect and Disease Control Guide."
2. Florida Extension Circular 196, "Chemical Weed
Control for Florida Vegetable Crops."
3. Florida Extension Circular 225, "Commercial
Vegetable Fertilization Guide."
4. Florida Extension Circular 153, "Commercial
Vegetable Variety Guide."
5. USDA Agriculture Handbook 303, "Market
Diseases of Asparagus, Onions, Beans, Peas, Carrots,
Celery, and Related Vegetables."
Since extension circulars are revised from time
to time, be sure to obtain latest editions.
The use of trade names in this publication is
solely for the purpose of providing specific infor-
mation. It is not a guarantee or warranty of the
products named and does not signify that they are
recommended to the exclusion of others of suita-
Prepared by: Stephen R. Kostewicz, Mason E.
Marvel, and James Montelaro in cooperation with
other personnel of the Institute of Food and Agri-
cultural Sciences. Special assistance was given by
D. S. Burgis, J. E. Brogdon, D. W. Dickson, R. S.
Mullin, and W. L. Currey.
^?4 MAY 61976
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMIC
(Acts of May 8 and June 30, 1914)
Cooperative Extension Service, IFAS, University of Florida
and United States Department of Agriculture, Cooperating
Joe N. Busby, Dean
This public document was promulgated as
an annual cost of $561.00, or .0561 cents per
copy to inform county extension directors
and vegetable growers.