University of Vermont Extension
Department of Plant and Soil Science
Dr. Leonard Perry, Extension
University of Vermont
of watermelons and the images that come to mind for many are warm
picnics, barbeques, and outings with family and friends. Although a
warm climate crop, there are
watermelons you can grow in the north. For
the best success, follow a few simple steps, beginning in May.
gardeners start watermelons from seeds, so the first step is to
right cultivars (cultivated varieties).
There are 4 main types of watermelons.
“Picnic” ones are the largest, ranging from 15 to 50 pounds, and
shapes varying from rounded to oblong.
“Icebox” ones are smaller, 5 to 15 pounds, and rounded—thus fitting
better in refrigerators, known in the past and still by many as
“iceboxes”. Newer ones are seedless, in varying shapes and
from 10 to 20 pounds. Seedless ones came
about in the early 1990’s, and today half of all watermelons sold in
seedless. Then there are those with
yellow or orange flesh inside. Expect one or two fruits per plant,
for seedless selections.
need a long growing season, for most cultivars, of 80 to 100 days.
If you’re gardening in a cooler climate with
shorter growing season, consider selections that mature 75 to 80
days from transplanting.
‘Sugar Baby’ is a standard of the small watermelons with rounded
fruit, only 6
to 8 inches wide and 8 to 10 pounds, and a dark green rind. ‘Sweet
Beauty’ has smaller, oblong fruit in
green with darker stripes. ‘Sweet Favorite’ has slightly larger
‘Sugar Baby’, oblong and bright green with dark stripes. Similar
only with rounded fruit is the hybrid
unique colors, ‘Sunshine’ is a small hybrid similar in size to
‘Sugar Baby’ but
yellow flesh, and light green rind with dark
stripes. ‘Sorbet Swirl’ is a newer
hybrid, with oval fruit to about 10 pounds, and flesh in swirls of
red and yellow. ‘Faerie’ has small fruit of 4 to 6 pounds
with an oblong shape, red flesh, and yellow rind; and, they may
mature in about
watermelons like warm to hot climates, you’ll want to wait until the
reaches about 70 degrees (F) before sowing or planting out. Since
in the north this may be early summer,
you can get a jump on the season a couple of ways. Sow seeds
indoors mid to late May in most
areas-- 2 to 3 weeks before planting out.
To warm the soil where you’ll plant, cover your garden soil outside,
about the same time as you sow indoors, with black plastic.
starting seeds indoors, use peat pots that you can plant directly in
the ground. Sow a couple seeds per pot, in a soilless
medium. Don’t start too soon, as plants
will get too large and their growth will be set back at
transplanting. Place pots in a sunny window, or under lights
(on 16 hours a day) on a heating mat which you can buy in garden
online. Ideally, soil temperatures in
your pots should be 75 to 80 degrees.
Once seeds germinate, keep watered, and as plants start to form
give a half-strength solution of fertilizer of your choice.
planting outside, work plenty of compost or composted cow manure
into the soil,
and add a balanced fertilizer such as 5-3-4 or 10-10-10 (4 or 3
respectively, per 100 square feet). If
sowing seeds directly, sow 2 or 3 seeds in a shallow mound. Space
the mounds (or plants if planting
seedlings) 3 to 4 feet apart, in rows 8 feet apart. The smaller
melons can be grown closer—2 feet
apart in rows 4 feet apart. To minimize any soil, pest, or disease
don’t plant watermelons in the same bed or space where you had
melons, or squash in the previous year or two.
of many cultivars can reach 20 feet long, so need plenty of space.
There are some newer cultivars such as ‘Sugar
Baby’ with vines only 3 to 4 feet long, and ‘Sweet Beauty’ or
‘Faerie’ with vines 9 to 10 feet long. Look for such shorter vining
you’re short on space. Or, consider
growing up a “sturdy” trellis, as made from pipes or 2x4 lumber.
For such upright vines, support the heavy
fruit with slings made from netting or cloth.
planted outside and watered, cover with a lightweight row cover
can find in many garden stores. This has two purposes—to help
soil heat, and to keep cucumber beetles and vine borer moths away.
Make sure to uncover plants, though, when
flowering so honey bees and other insects can pollinate them.
need at least an inch of water a week, from you if not from rain.
You’ll want to water with fertilizer
according to the label, or “side dress” dry fertilizer around
vines start growing and when fruits are maturing. Use a dry
fertilizer such as 5-3-4 analysis
at the rate of 2 pounds per 100 square feet of garden area at each
application. When fruits start to
mature, use less water so melons will become sweeter.
are 3 ways to check if your watermelon is ripe.
When the curly tendril closest to the fruit stem turns brown and
up, the watermelon “may” be ripe, however, for some cultivars this
week before fruit are fully ripe. Most
common is to tap or thump the melon with your fingers, a ripe fruit
soft hollow sound or “thunk” instead of a higher-pitched “ping”.
Perhaps best is to check the bottom of the
fruit where it rests on the ground. This
area turns from almost white to yellowish when fruit are ripe. Ripe
their slick or powdery surface, taking on a dull appearance.
are best chilled and eaten fresh. Cut, they’ll store up to 4 days
plastic in the refrigerator. Uncut,
they’ll store 10 days or so.
are great to quench summer thirst, being up to 92 percent water.
They are healthful, being rich in vitamins A,
B6, and C plus other beneficial minerals and compounds. They’re
rich in lycopene, an antioxidant that may
reduce the risk of some diseases such as
prostate and breast cancers, heart disease, and asthma. An amino
acid in watermelon (citrulline) may help boost the immune system.
Studies have shown that watermelon can protect
vision loss, even more so than eating carrots. These possible
benefits do not substitute, of
course, for medical advice from your doctor if you have such
year the National Garden Bureau chooses a flower and vegetable to
2013 being the Year of the Watermelon.
More information on this crop, as well as others from the past, can
found on their website (www.ngb.org).