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
Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / John T. Woeste, Dean
Florida leads the nation in watermelon production,
producing about one-third of the watermelons in the
United States from annual plantings of 45 to 65 thou-
sand acres. This accounts for three-quarters of the
nation's spring production. Commercial watermelon
production of 500 acres or more occurs in at least 22
counties. Harvesting usually begins in April or May
in south Florida and progresses to north and west
Florida by July. From 55 to 70% of the total produc-
tion is harvested in June. A very small acreage is
planted for fall harvest. Since watermelon prices
change rapidly with fluctuations in supply and
weather, growing watermelons is quite speculative.
The use of archaic harvesting and transportation
methods results in high labor cost and uncertain con-
This listing does not imply that other cultivars are
not adapted to Florida. For more detailed cultivar
trial results consult Florida Experiment Station Cir-
cular S-304, Vegetable Variety Trial Results in
Charleston Gray, Charleston Gray #5, Prince
Charles (Fl). 20-35 lb. Fruits long, light gray-green
rinds that are relatively thin, hard and tough. Brown
to black seeds, bright red flesh with good flavor and
excellent texture. Outstanding shipping qualities.
Resistant to anthracnose and fusarium wilt. Very
slow to sunburn.
Crimson Sweet. 20-30 lb. Almost round, blocky,
light green rind with dark green stripes. Flesh is
bright red, sweet, firm and fine textured with small,
dark brown seeds. Rinds are thick and shipping
qualities excellent. Resistant to anthracnose and
Jubilee. 25-35 lb. Fruits long, rinds hard, tough
and green with dark green stripes. Flesh is bright red,
with good flavor, excellent texture and large, black
seeds. Well adapted to shipping. Resistant to anthrac-
nose, and new strain has greater resistance to
Dixielee. 20-30 lb. Almost round, light green rind
with narrow, dark green stripes. Flesh is exceptional-
ly firm, sweet and very dark red with black seeds.
Slightly later maturing than Charleston Gray. Ship-
ping quality good when harvested at the proper
maturity. Resistant to anthracnose, and highly resis-
tant to fusarium wilt.
Sugarlee. 15-20 lb. New cultivar recommended for
trial plantings. Round melon, light green rind with
dark green stripes. Special attributes: earliness and
long holding of good internal quality on the vine.
Flesh is bright red and sweet with large, black seeds.
Resistance similar to Charleston Gray and Crimson
Dec 15 to Mar 1
Jan 15 to Mar 15
Distance between rows (ft)
Distance between hills (ft)
Seeding depth (in)
Seed required/acre (Ib)
Days to maturity
Feb 15 to Apr 15
*Extension Vegetable Specialist and Retired Extension Vegetable Specialist, Vegetable Crops Department, Institute of Food and Agricultural
Sciences, University of Florida, Gainesville.
Circular 96 G
Ft- 14 i1Y
.F ,.1.S^' n R .K,_rSb~ alter*
Watermelon seeds germinate at soil temperatures Soil pH and Liming. Optimum pH range for
of 68 o to 95 o F, but germination is very slow below watermelon production is 6.0 to 6.5. When cleared
700. Spring planting should wait until the soil is suf- and brought under cultivation, many flatwood soils
ficiently warm; however, earliness of production is such as Myakka, Leon and Immokalee are extreme-
very important in securing maximum economic ly acid with values as low as pH 3.5. Better-drained
returns. Young plants are very tender and easily in- soils such as Lakeland tend to be less acid with an
jured by frost. To reduce risk from early plantings, average of pH 5.0 or above. A soil test is essential
a second seeding can be made about one week after on all land where the acidity and nutrient status is
the first with the seeds a few inches from the, original not known. Watermelon seed planted in very acid
planting. The time between planting and:iharvest' '-sbils germinate but generally die before the second
depends primarily on temperatures and cultivars. or third true leaves develop. Response to lime on
Sandy soils that warm up earlier in thospring also: such acid soils is quite marked.
reduce the time required for seedling emergence. Calcium is mobile but since the downward move-
The amount of seed required depends upon seeId nent of calcium in the soil is slow, lime must be
size, germination and plant -spacing. 'l ni'i' thoroughly incorporated in order to neutralize the
vigorous seed with a germination of 85-to'9t(Y% i'sre- soil acidity in the root zone. Lime should be applied
quired for high yield and early harvest. All seed broadcast and worked into the soil to a depth of 6
should be treated to protect the seed and young to 8 inches for maximum growth and yield response.
seedlings from decay. For seed not treated by the Generally, it is desirable to apply lime at least one
seedsmen, multipurpose kits are available for con- month before seeding. However, studies have shown
trol of root rots, mice and birds. These are particular- that where lime was needed, it could be applied one
ly important for seed planted in cool soil that requires day before seeding with beneficial results. The form
longer emergence periods. Watermelons transplant of lime used can also be determined from the soil
poorly, with slow formation of new roots; however, test. If the Magnesium (Mg) level is low, dolomitic
container-grown seedlings may be transplanted limestone should be applied rather than calcic
when direct-seeded plants are lost and it is too late limestone.
to plant additional seed. Micronutrients. A general guide for adequate
When several seeds are planted in each hill, the micronutrients in mineral soils is the addition of 5
plants should be thinned to one or two per hill, lbs. of Manganese (Mn), 4 lbs. of copper (Cu), 4 lbs.
depending upon local conditions. Closer spacing pro- of iron (Fe), 3 lbs. of zinc (Zn) and 1.5 lbs. of boron
duces higher yields when irrigation and high fertiliza- (B) per acre to the fertilizer mixture. These micro-
tion rates are used. Melon size usually increases with nutrients can be obtained from mixtures of oxides,
increased space between plants, but market demand sulfates and chelates. Watermelons grown on new
may be greater for 15 to 25 lb. sizes than for larger sandy and flatwood soils generally develop copper
melons. A near perfect stand and good foliage cover deficiency unless fertilizer containing Cu is used.
are very important and hand thinning one or more
times may be desirable. Copper. Copper is a second limiting factor for
Placement and Timing. Watermelon is a heavy
feeder and yield increases can be expected from in-
creased fertilization if applications are based on soil
tests and previous cropping. Watermelons respond
better to split applications of fertilizer as follows:
(1) Broadcast one-half of the basic fertilizer (N-
P2,O-K20) in a 4-foot swath in the middle of the
row and work well into soil before seeding.
(2) When the vines develop runners, make the se-
cond application in swaths on each side one to
two feet ahead of vine tips and work into the
(3) Apply supplemental nitrogen and potash as re-
quired, especially after heavy, leaching rains.
watermelon production on many sandy soils in
Florida. Yield responses to organic sources of N such
as castor pomace, activated animal tankage and
sewage sludge have been reported in the past. Max-
imum production was limited until it was found that
this yield-increasing response was due to
micronutrients supplied by the organic-N source.
Copper was found to be largely responsible for the
Watermelons grown on very deficient virgin san-
dy soils generally develop severe Cu deficiency
without Cu-containing fertilizer. Deficiency symp-
toms become evident as early as the two- to four-true
leaf stage. Symptoms consist of upward cupping and
crinkling of the young expanding leaves and death
of the leaf tips. As growth continues, internodes are
shortened, and because of necrosis of leaf tissue, leaf
shapes are irregular. When Cu deficiency is less
evere, symptoms do not develop until later growth
tages and generally during periods of rapid growth.
expandingg leaf tips become necrotic as the Cu supply
s depleted. Flower development and fruit set are
;reatly reduced on Cu deficient plants.
Response to Cu varies considerably with soil type
ind is greatest on poorly drained sandy soils and less
>n better drained upland soils.
Copper can be applied with the fertilizer, directly
o the soil, or as a foliar spray, but mixing throughout
he plant bed is superior. A total of 4 lbs. of Cu per
icre should provide the continuous Cu supply that
s needed throughout the season.
Soil Application Supplemental Application
Actual Actual lb No. of
Ib/acre Each Applications
Mineral Soils1 180-240-240 -
Mineral Soils2,3 120-160-160 15-0-30 1 to 4
Rockland 60-80-80 30-0-30 1 to 3
Includes all irrigated mineral soils (except marl and rockland) us-
ing polyethylene-mulched beds.
i Includes all irrigated mineral soils (except marl and rockland) us-
ing open ground culture.
1 On the acid flatwood soils in south Florida, P205 may be increas-
ed to 200 to 240 Ibs for the early spring crop.
Timely irrigation on sandy soils with high levels
)f fertilization is extremely important. Plants pro-
Juce larger yields and larger watermelons with
Fewer defects, such as blossom-end rot, when the
moisture supply is uniform and plants do not come
inder water stress. Portable, overhead sprinkler ir-
rigation systems are used extensively except in
south Florida where seepage irrigation is available.
Watermelons require insect pollination for fruit
set and proper development of fruit shape and size.
Honey bees are the most dependable pollinators
when properly managed and tend to collect pollen
From a single species of flower that is near their
hive. Pollination is improved when bees visit female
flowers 8 or more times. Use one active hive of bees
for every 3 to 5 acres of watermelons. Wait until
plants begin to blossom, then move hives into the
field and distribute them for uniform coverage of
the crop by the bees. Bees require water for sur-
vival and their efficiency can be improved by a
water source near the hive. Apply insecticides in
late afternoon after bee activity diminishes to
minimize bee kills. Bee activity in the field should
be checked frequently to be sure the melon flowers
are being pollinated.
Fusarium wilt continues to be a serious problem
requiring watermelons to be grown on new land or
in a rotation of at least 8 years between watermelon
crops. Other "old land" problems include
nematodes, weeds and wind erosion.
Nematodes. Watermelons are susceptible to
nematode injury and soils heavily infested with
nematodes should be avoided. Nematodes may
cause short, stubby or galled roots and the plants
may be stunted, chlorotic and prone to wilt during
hot weather, even when soil moisture is adequate.
If plant and root observations indicate nematode
problems, have soil and root samples examined to
determine if they are present. If nematode-infested
soil must be used, it should be treated as suggested
in the Florida Extension Nematode Control Guide.
Insects. Watermelons can often be grown without
much injury from insects, although there are many
insects that may cause damage. These include soil
insects such as cutworm, mole cricket and
wireworm; foliage and stem feeders such as ar-
myworm, cucumber beetle, leafhopper, leafminer,
aphids and mites, and rindworms such as tobacco
budworm, cutworm, cabbage looper and
pickleworm. Cutworms may be destructive to small
melon plants or scar the rind of developing melons.
Aphids cause direct damage as sap feeders and
spread watermelon mosaic virus. Rindworms should
be given special attention because one hole in a
melon makes it unmarketable. Insect control is best
accomplished by periodic scouting of fields and ap-
plication of insecticide as suggested by your County
Extension Agent or the Florida Extension Insect Con-
Diseases. Watermelons are generally subject to
diseases that often destroy much of the crop. The
major diseases caused by fungi anthracnose,
downy mildew, gummy stem blight, cercospora
leafspot, alternaria leaf spot and seedling blights -
have several recommended prevention and control
measures to be used before and after planting. A con-
trol program should include crop rotation, isolation
from other cucurbits, deep plowing, weed control,
resistant cultivars, seed treatment and fungicide
sprays. Fusarium wilt caused by a fungus in the soil
cannot be controlled by fungicides. The scarcity of
new land and cost of installing irrigation for one crop
decrease the production potential for watermelons.
Bacterial leafspot can be controlled by spraying,
but no control is available for rind necrosis.
Watermelon mosaic is caused by a virus that can be
transmitted mechanically but is generally transmit-
ted by aphids. It may be transferred to watermelon
from cucurbitaceous weeds or crop plants, including
other watermelons. Control is difficult, but isolation
from other cucurbits, killing of known weed hosts,
and avoidance of areas known to have had severe
mosaic occurrences in previous seasons are recom-
mended. Control of aphids in individual fields is not
effective in controlling mosaic since transmission of
the virus can be effected before the insects ingest
lethal doses of the insecticide. Disease control recom-
mendations can be found in Extension Plant
Pathology Report No. 15.
Physiological disorders. Blossom-end rot is the
name applied to a physiological or non-parasitic
disorder that is related to calcium deficiency in the
plant. Prevention recommendations include an ade-
quate supply of calcium through liming while main-
taining a uniform moisture supply to the plant.
Weeds. Weed growth and competition can be
severe, especially on old land. At the present time
adequate weed control can be obtained only through
the combined use of good field preparation, her-
bicides and cultivation.
With supplemental fertilizer applications, a shallow
cultivation can destroy small weeds and germinating
weed seeds. Care should be taken not to prune
watermelon roots, which can extend beyond the
ends of the runners. Updated herbicide listings can
be found in Circular 196, Weed Control Guide for
Commercial Vegetables in Florida.
HARVESTING AND HANDLING
Maturity and quality. Watermelons have a short
period during which maturity is satisfactory for
harvest. Desirable harvest qualities include sweet,
crisp flesh with red color. Maturity is reached when
the flesh is at least fairly sweet and shows the
characteristic color of a mature watermelon of that
cultivar. Sweetness usually develops concurrently
with red color. Crispness is associated with high
moisture content within undamaged cells that have
not separated to form air spaces, beginning around
the seeds. Flesh colors in immature fruits are white
to pink, mature watermelons are red or dark red and
orange colors indicate overmaturity in the cultivars
grown commercially in Florida. Harvested immature
fruits are very firm, do not yield readily to pressure
and will never develop acceptable sweetness. Liv-
ing, functioning vines are necessary to produce good
quality fruits and the vines should be kept healthy
as long as harvesting is continued.
Harvesting. Fruits for distant markets must be
harvested before full ripeness to minimize handling
damage, whereas watermelons for local, nearby
markets should be harvested fully ripe. Since ship-
ping qualities vary among cultivars and change with
advancing maturity, harvesting operations should be
coordinated with your buyer's requirements. Ex-
perience in selecting fruits for harvest is highly
desirable and they should be cut from the vine, not
Some indications of maturity are ground spot
changes from white to yellow, tendrils change from
green to brown and begin to dry, thumping sound
changes from a metallic ringing when immature to
a soft, hollow sound when mature. Cut a few melons
to compare flesh quality with external appearance.
As watermelons are harvested (cut) from the plant,
they should be carried to roadways through the field
and laid in rows. They should not be dropped, stood
on end, or allowed to remain in hot sun. Field trucks
should be well-padded with burlap or carpet on the
sides and 6 inches of hay or straw on the bottom.
Workers on the ground should pass fruit to a worker
in the truck who carefully places them in the load.
Bruising results when loaders throw fruit into the
truck. Loaders should never walk on watermelons
while loading nor ride on top of the load, even
though no visible damage occurs. Internal damage
during harvesting and handling seriously impairs
later appearance and eating quality.
Grading. Grade standards, effective since January
15, 1978, describe the requirements for U.S. Fancy,
U.S. No. 1 and U.S. No. 2 grades of watermelons with
two levels of optional quality to indicate "good" and
"very good" sweetness levels. To qualify for the
"good" internal quality requires not less than 8%
soluble solids and 10% is required for the "very
good" quality. Grade standards give industry a com-
mon language for buying and selling, but unfor-
tunately Florida growers and shippers have mostly
discontinued using U.S. or any grade standards that
indicate consumer qualities. It would benefit the in-
dustry if minimum sugar contents were voluntarily
adhered to by growers.
This public document was printed at a cost of $878.00, or 15.9 cents per copy, to inform interested commercial
growers on watermelon production in Florida. 1-5.5M-85
COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL -1
SCIENCES, K. R. Tefertlller, director, In cooperation with the United States Department of Agriculture, publishes this Infor-
mation to further the purpose of the May 8 and June 30, 1914 Acts of Congress;and Is authorized to provide research, educa- IFAG
tional Information and other services only to Individuals and Institutions that function without regard to race, color, sex or
national origin. Single copies of Extension publications (excluding 4-H and Youth publications) are available free to Florida
residents from County Extension Offices. Information on bulk rates or copies for out-of-state purchasers Is available from --
C. M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Galnesville, Florida 32611. Before publicizing this
publication, editors should contact this address to determine availability.
Field truck loads of watermelons are hauled to a
local grading and packing site, unloaded, divided into
sizes, inspected according to buyer specifications and
loaded on highway trucks for transport to market.
Containers. Watermelons generally have not been
shipped in containers, but cartons holding 2 to 5 fruit
and bulk bins holding 800 to 2,000 pounds are gain-
ing in popularity. The trend toward standardized and
unitized shipping containers in the produce industry
has several advantages for watermelons.
1. Less labor with quicker unloading and handling.
2. Better utilization of trucks and dock space at
terminal markets, which would increase
availability of trucks.
3. Less fruit damage and better quality.
Large wood and fiberboard bins on pallets or slip-
sheets are available. Melon cartons need to accom-
modate wide ranges in melon dimensions, maximize
utilization of the 48 x 40 pallets and have sufficient
strength to carry 50 to 75 pounds under high humidi-
Shipping and Storage Conditions. Watermelons
are not adapted to long storage and should be con-
sumed within 2 to 3 weeks after harvest.
Temperature management is important for optimum
storage. Watermelons should be protected from sun-
burn by prompt field handling after harvest and
shading while waiting for shipment. Temperatures
above 90 F result in flesh breakdown and increas-
ed decay. At temperatures below 500, chilling injury
causes decreased redness, juice leakage and decay.
Transit temperatures of 55 to 70 F with ventilation
are recommended and refrigeration is not required.
Most watermelons are transported from Florida in
open or closed trucks and trailers without refrigera-
W:i ,.,IIielons should not be shipped or stored with
fruits that emit ethylene because this gas causes flesh
softening and poor flavor. Watermelons sliced for
retail sales storage should be overwrappcd with film
and stored at 32 0F.
Additional information and details on local applica-
tion can be obtained from your County Extension