Watermelon in Zone 4 -- plant

Beginner

Know your soil

Your soil

Identify yours

Not sure what soil you have? Grab a small handful of damp soil from your garden bed and squeeze it. If it crumbles apart easily, it's sandy. If it holds together but breaks when you poke it, it's loam (what most vegetables want). If it stays in a hard, slippery ball, it's clay.

What this crop wants

Plant watermelon in light, well-drained soil that warms up fast, like a sandy loam, with some compost mixed in. Avoid going overboard on rich, high-nitrogen material, because that gives you lots of leaves and vine but less fruit. Many gardeners plant on low hills or raised mounds, which warm up and drain better and keep the fruit off soggy ground. If your soil is heavy clay, it stays cold and wet and can bring on disease, so mix in compost and build the soil up into mounds, or pick the sandiest, best-draining spot you have.

If your soil doesn't match

You have sandy soil

Mix 2-3 inches of compost into the top 6 inches of your bed before planting. Compost holds moisture (which sandy soil drains too fast) and adds the nutrients sandy soil tends to lack. Repeat each season. Compost breaks down over time.

You have clay soil

Mix 2-3 inches of compost AND a few inches of coarse sand or perlite into the top 6 inches of your bed. The compost feeds the plants; the sand breaks up the clay so air and water can move through. Don't add sand without compost. It can compact like concrete.

Containers and raised beds

If amending your soil sounds like too much work, or if your soil is heavy clay, full of rocks, or contaminated, build over it. A raised bed at least 12 inches deep filled with a 50/50 mix of compost and sandy loam gives you ideal growing soil with no battles. A 5-gallon container with quality potting mix does the same for one plant at a time. Both bypass your native soil entirely.

Learn more about your soil

The specs

Care guide

The numbers that matter, at a glance.

Sunlight

Full sun · 8-10 hrs/day

Water

moderate

Spacing

36-72 inches

Soil

sandy loam

Days to maturity

70-95 days from transplant

Soil pH

6 to 6.8

Container OK?

Yes · 15+ gal pot

Germination temp

70-95°F

Soil chemistry

Soil pH for watermelon

Preferred

6 to 6.8

Tolerated

5.5 to 7.5

Watermelon likes soil that is slightly acidic to neutral, about pH 6.0 to 6.8, and most garden soil is already close. An inexpensive soil test tells you where you stand and whether you need to adjust it before planting.Watermelon grows best in slightly acidic to neutral soil, around pH 6.0 to 6.8, and tolerates a wider band of roughly 5.5 to 7.5. It is a little more forgiving of mildly acidic ground than many vegetables, but strongly acidic or strongly alkaline soil tightens nutrient uptake. Test before planting and lime or add sulfur only on the test's advice rather than by guess.

Verified · 2 sources View

Steady hand on the hose

Watering

When & how much

Frequency

Give watermelon about 1 to 2 inches of water a week, more when it is hot and dry. Water deeply rather than a little every day, since the plant roots deep and the fruit is almost all water.Aim for about 1 to 2 inches of water per week, more in heat or on sandy soil, delivered deeply and less often rather than in light daily sprinkles. Watermelon is deep-rooted, with the bulk of its roots in the top 12 inches, and the fruit is about 92 percent water, so steady moisture through fruit sizing is essential.

Amount

About 1 to 2 inches of water a week is a good target, more while the plant is flowering and the melons are growing.Around 1 to 2 inches per week is the working range, leaning higher during flowering and fruit sizing and through hot, dry spells. Even, deep watering builds large, well-filled melons; let the plant swing dry and you get poor set, small fruit, and blossom-end and hollow-heart problems.

Method

Water the soil, not the leaves, using a soaker hose or watering wand at the base, which helps prevent leaf disease. As the melons get close to ripe, ease off the water. That last step is what makes watermelon sweet, since too much water near harvest waters down the flavor and can crack the fruit.Water at the base with drip or a soaker hose, keeping the foliage as dry as possible, since wet leaves invite anthracnose, gummy stem blight, and the mildews that watermelon is prone to. The key move unique to watermelon is to taper watering as the fruit approaches ripeness, which concentrates the sugars and sweetens the flesh, while over-watering near harvest dilutes flavor and can split fruit.

Signs of trouble

Too much water

If lower leaves yellow, the plant wilts even though the soil is wet, stems go soft, or the melons split or taste watery, it is getting too much water or the soil drains poorly.Yellowing lower leaves, wilting even when the soil is wet, soft or rotting stems, and split or bland, watery fruit point to overwatering or poor drainage. Saturated soil also favors Fusarium wilt and fruit rot, especially on heavy ground.

Too little water

Some midday wilting in hot weather is normal and passes by evening. Leaves that stay wilted mean the plant is too dry, and drought while fruit is forming gives small, misshapen melons.Midday wilting that recovers overnight is normal in heat, but leaves that stay limp and dull signal real drought. Dry spells during fruit sizing show up as small, misshapen melons, aborted young fruit, and blossom-end problems.

Feeding rhythm

Feeding

Frequency

At planting, then side-dress once or twice

Type

lower-nitrogen at planting, then nitrogen side-dress

When to start

Work into the bed before planting, then side-dress when vines begin to run and again at flowering

Watermelon does not need a lot of nitrogen, and too much gives you big leafy vines but fewer, less sweet melons. Mix a fertilizer that is lower in nitrogen, like a 5-10-10, into the soil before planting, then give the plants a little nitrogen when the vines start to run and again when flowers appear. Once the melons start to form, stop pushing nitrogen so the plant puts its energy into growing sweet fruit instead of more leaves.Watermelon is a moderate feeder that wants more phosphorus and potassium than nitrogen, since excess nitrogen drives leafy vine at the expense of fruit set and sugar. Work a lower-nitrogen complete fertilizer such as 5-10-10 into the bed before planting (Clemson suggests about 30 pounds per 1,000 square feet), then side-dress with a nitrogen source as the vines begin to run, and again lightly at flowering. Ease off nitrogen once fruit has set so the plant pours its energy into sizing and sweetening the melons rather than growing more vine. Pair feeding with even moisture, because the nutrients only help a plant that is not also drought-stressed.

N · P · K = 5-10-10

Use a lower-nitrogen fertilizer like 5-10-10 at planting, then a little nitrogen as the vines spread. Do not overdo the nitrogen once melons form, or you get leaves instead of fruit.A lower-nitrogen complete fertilizer such as 5-10-10 worked in at planting, then a nitrogen side-dress as the vines run and again lightly at flowering, easing off nitrogen once fruit sets. Too much nitrogen gives vine and leaf at the expense of fruit and sweetness.

Try 5-10-10 at planting, then a nitrogen source such as calcium nitrate or blood meal

Who grows well together

Companion planting

The most useful watermelon companions are flowers that bring in bees, since watermelon needs lots of bee visits to set fruit (especially seedless kinds, which depend on bees carrying pollen from a seeded variety). Bush beans add a little nitrogen, and nasturtiums can lure pests away. The one rule that really matters is to keep watermelon away from other melons, cucumbers, and squash, which all share the same pests and diseases. Most watermelon companion pairings are traditional rather than trial-tested, and the ones worth acting on serve two practical ends: pollination and pest pressure. Because watermelon fruit set is strongly pollinator-limited, flowering insectary plants like borage near the patch are a genuine help, and that help is doubly important if you grow seedless types, which lean entirely on bees moving pollen from a seeded pollinizer. Bush beans fix nitrogen the crop can use without the heavy feeding that would otherwise grow vine over fruit, and a trap planting of nasturtium can divert cucumber beetles and other pests. The firmest rule is a rotation one: keep watermelon away from other cucurbits, which share its pest and disease complex, including the soilborne Fusarium wilt and the foliar anthracnose and gummy stem blight that build up where melons follow melons.

Other

Borage

Borage flowers are loved by bees, and watermelon needs lots of bee visits to set fruit, so a few borage plants nearby can help with pollination. This matters most for seedless watermelon, which depends on bees.A strong bee magnet whose flowers recruit the pollinators watermelon fruit set depends on, which is especially valuable for seedless types that rely on bees moving pollen from a seeded pollinizer. Pollinator-habitat value is well grounded; the specific borage-watermelon pairing is traditional rather than trial-tested. Well-grounded

Bush beans

Beans pull nitrogen from the air into the soil, which watermelon can use, and they do not share watermelon's pests. A good, traditional neighbor.Bush beans fix nitrogen that lightly benefits the crop without the heavy nitrogen that would push vine over fruit, and they share none of the cucurbit pests. A traditional, mechanistically plausible pairing rather than a trial-isolated one. Well-grounded

Nasturtium

Nasturtiums are often grown near melons and squash to lure cucumber beetles and other pests away, and their flowers bring in bees. A helpful, low-risk neighbor.Often planted near cucurbits as a trap and deterrent for cucumber beetles, and its flowers also draw the bees watermelon depends on for fruit set. Trap cropping is a documented principle, but the specific nasturtium-watermelon effect is not formally isolated, so treat it as a plausible aid. Well-grounded

Corn

Corn is the traditional Three Sisters partner that gives sprawling vines something to grow among. With watermelon it is more tradition than a proven boost, and watermelon's full-sun need means you should not let corn shade it much.The classic Three Sisters partner, though the fit is looser for watermelon than for shade-tolerant squash: tall corn can give the trailing vines structure, but watermelon wants full sun to sweeten, so keep corn from shading the patch. A long-standing intercropping tradition with a space rationale, not a measured yield effect for this pair. Traditional

Keep apart from

Other cucurbits Keep watermelon away from other melons, cucumbers, and squash. They share most of the same pests and diseases, so planting them together makes those problems worse.Cucumber, muskmelon, squash, and pumpkin share watermelon's pest and disease complex, including cucumber beetle, aphid-spread mosaic viruses, the mildews, and the soilborne Fusarium wilt and foliar anthracnose and gummy stem blight that build up where cucurbits repeat. Grouping them concentrates that pressure. A real epidemiology and rotation principle rather than a tested adjacency effect: spread cucurbits out and rotate them on a long cycle. Well-grounded

Potatoes Some gardeners keep potatoes and melons apart, since both are hungry plants and potatoes can bring their own diseases. This is more tradition than a proven rule.A traditional caution that potatoes and cucurbits compete heavily and that potatoes can harbor disease and attract pests near melons. There is no strong T1 mechanism for the specific pairing, so it persists mostly as garden lore. Traditional

Provenance tagged inline · see methodology for the labeling system Key

Harvest signals

When to pick

You pick a watermelon once, when it is fully ripe, and it will not get any riper after you cut it, so timing matters. Look for several signs together: the little curly tendril closest to the melon dries up and turns brown; the pale spot where the melon sits on the ground turns creamy yellow instead of white; the skin goes from shiny to dull; and the melon makes a deep, dull thump when you tap it, instead of a tight, high ring. Cut it off the vine with a knife, leaving a short piece of stem, rather than pulling it. The browning tendril and the yellow ground spot together are the most reliable check.Watermelon is harvested once, at full ripeness, and does not ripen further after cutting, so reading the plant correctly is everything. No single sign is perfect, so use several together: the curly tendril nearest the fruit dries up and turns brown; the ground spot where the melon rests on the soil turns from white or pale green to a creamy, buttery yellow; the skin loses its gloss and dulls to a matte finish; and a ripe melon gives a deep, dull, hollow thump when tapped (an unripe one rings tight and high). The melon should also have reached full size and color for its variety. Cut the fruit from the vine with shears or a knife leaving a short stub of stem rather than pulling it, since watermelon does not slip from the vine. When in doubt, the browning tendril plus a yellow ground spot is the most reliable pair.

Verified · 3 sources View

Yield

What to expect

A full-size watermelon plant usually gives you 2 to 4 melons, while small icebox types make more, smaller ones. Each plant needs a lot of room. If you want bigger melons, keep just two or three fruit per vine so the plant can size them up.A healthy full-size watermelon vine typically yields 2 to 4 marketable melons, while icebox and bush types set more, smaller fruit. Limiting fruit to two or three per vine on full-size types channels energy into larger, better-filled melons. Plants need plenty of room, roughly 24 square feet each for full-size types, and even moisture and modest feeding through sizing build sweet fruit.

Unlike summer squash, watermelon does not keep producing all season. The plant sets its fruit over a few weeks and the melons ripen over a stretch in mid to late summer, and you pick each one once when it is ripe.Watermelon does not produce continuously; the plant sets fruit over a few weeks and then sizes and ripens that crop, with the melons coming ready over a window in mid to late summer rather than all at once or all season long. Each melon is harvested once, at full ripeness. The big first-year surprises are how far watermelon vines spread, how much they depend on bees, and how tricky it is to tell when a melon is ripe (it will not ripen after you pick it). Give them lots of room, grow some flowers for the bees, and learn the ripeness signs before cutting.The usual first-year surprises are how much room the vines take (8 to 12 feet for full-size types), how pollinator-dependent fruit set is, and how much ripeness judgment matters, since the melon does not finish off the vine. Give plants far more space than seems necessary, grow flowers nearby for bees, and learn the tendril-and-ground-spot check before you cut.

What changes yield

Heat and season length: watermelon needs a long, hot season (70 to 95 days) with warm nights to ripen and sweeten; cool-summer northern and coastal areas are marginal and need early icebox types, transplants, and black plastic mulch.Pollination: fruit set is pollinator-limited, each female flower needing many bee visits, and seedless types additionally need a seeded pollinizer nearby; poor pollination drops or deforms young fruit.Space and vine vigor: full-size vines sprawl 8 to 12 feet and need about 24 square feet each; crowding cuts yield and worsens disease.Disease pressure: Fusarium wilt, anthracnose, gummy stem blight, and the mildews can end a planting early, so resistant varieties and long rotations matter.Even moisture, then a dry finish: steady water through sizing builds full melons, but tapering water near ripeness is what concentrates the sugars and makes them sweet.

Verified · 2 sources View

Pick your variety

Recommended varieties

Pick a watermelon by your summer and your space. If your season is short or cool, grow a fast small type like Sugar Baby or Yellow Doll. If you have a long, hot summer and room to spread, grow a big one like Crimson Sweet, Charleston Gray, or Jubilee. In the South, choose disease-resistant varieties like Crimson Sweet. Seedless watermelons are sweet and convenient, but remember they need a regular seeded variety planted nearby to pollinate them, and they like it extra warm.Choose by season length, space, and use. Where summers are short or cool, lean on the fast icebox types such as Sugar Baby and Yellow Doll, which ripen in 70 to 80 days; in long, hot regions the full-size Crimson Sweet, Charleston Gray, and Jubilee reward the heat with big, sweet melons. In the disease-prone Southeast, prioritize varieties with anthracnose and Fusarium wilt resistance such as Crimson Sweet, Charleston Gray, and Jubilee. Seedless types are popular and sweet but add a real requirement: a seeded pollinizer must be grown alongside, and they want the warmest conditions to germinate and finish.

Sugar Baby

A classic early icebox watermelon, round and dark green with sweet red flesh, about 8 to 10 pounds. Quick to mature, which makes it the go-to for shorter or cooler-summer gardens and the North. Open-pollinated and seed-saveable.

Crimson Sweet

The dependable home-garden standard: round-oval, light-and-dark green striped, 15 to 25 pounds, with very sweet red flesh. Carries resistance to anthracnose and Fusarium wilt, which makes it forgiving in the Southeast. Open-pollinated.

Charleston Gray

The classic long, oblong gray-green watermelon, 20 to 30 pounds, with sweet red flesh, a tough rind, and good heat and drought tolerance plus anthracnose and Fusarium wilt resistance. A strong choice for hot regions and long seasons.

Jubilee

A large oblong striped watermelon, 25 pounds or more, with crisp, sweet red flesh and Fusarium wilt and anthracnose resistance. A long-season Southern favorite where there is room and heat to finish it.

Yellow Doll

An early yellow-fleshed icebox hybrid, small at around 5 to 8 pounds, very sweet, and fast to ripen. A good pick for short seasons, small gardens, and gardeners who want something different.

Seedless (triploid) types

Seedless hybrids such as the Crimson-type triploids ripen in roughly 85 to 90 days and produce no viable pollen of their own, so they must be planted alongside a seeded pollinizer variety (commonly one seeded plant per two to three seedless). Sweet and convenient, but they need warm conditions to germinate and a longer, hotter season.

Off the vine

Storing your harvest

Room temp

A whole, ripe watermelon keeps at room temperature for about a week. It does not store for months like a pumpkin, so eat it within a week or so of picking, and keep it out of direct sun.An uncut, ripe watermelon holds at room temperature for about a week, or 7 to 10 days, kept out of direct sun. Unlike winter squash, it does not improve or keep for months, so plan to eat it within a week or so of picking. Whole melons hold a bit longer in a cool room than a warm one.

Fridge

A whole watermelon keeps for up to about 2 weeks if held cool, around 50 to 60°F. Do not keep it very cold for a long time, since that harms the flesh. Once you cut it, wrap the pieces and keep them in the fridge, using them within a few days.A whole watermelon keeps about 2 weeks held cool at around 50 to 60°F, the practical limit before flavor and texture decline; do not store it very cold for long, as watermelon is subject to chilling injury below about 50°F. Once cut, wrap the pieces tightly and refrigerate, using them within 3 to 5 days.

Freezer

Watermelon turns mushy if you freeze it in chunks, so it is best frozen as juice or puree. Blend the flesh and freeze it in portions for slushies and drinks, or freeze cubes to drop into a glass like ice.Watermelon does not freeze well as chunks, since freezing collapses the crisp texture into mush, but it freezes nicely as puree or juice: blend the flesh, strain if you like, and freeze in portions for slushies, granita, or agua fresca. Frozen cubes also work for chilling drinks.

Verified · 2 sources View

When something goes wrong

Common problems

The watermelon was not sweet insideCut the melon open and it was bland, pale, or watery

01 of 04

What happened The melon was picked too early, or it got too much water right before harvest. Watermelon does not get sweeter after you cut it, and too much late water makes it watery.The melon was harvested under-ripe, or it was over-watered near harvest. Watermelon does not sweeten off the vine, so a melon picked early stays bland, and heavy watering in the final week dilutes the sugars and can leave the flesh watery. Next season Wait for the ripeness signs to line up before picking, and ease off the water in the last week or two so the melon sweetens.Learn the ripeness signs and use several together (browned tendril, creamy-yellow ground spot, dull skin, dull thump), and taper watering in the last week or two before harvest to concentrate the sugars.

The vine wilted and died even though it was wateredVine yellowed and wilted on one side and died

02 of 04

What happened Usually Fusarium wilt, a soil disease that only attacks watermelon and blocks the plant's water pipes, so it wilts and dies even when watered. It builds up in soil where you grow watermelon too often.Most likely Fusarium wilt, the watermelon-specific soilborne fungus that clogs the water-conducting tissue, often killing one runner first, then the plant, even in moist soil. A pinkish mold near the soil line and browned vascular tissue in a cut stem confirm it. It builds up where watermelon repeats on the same ground. Next season Grow resistant varieties, do not plant watermelon in the same spot for at least five years, and look into grafted plants if the disease keeps coming back.Plant resistant varieties, rotate out of watermelon and cucurbits for at least five years, and consider grafted plants on resistant rootstock where the disease is established.

Little melons turned yellow and fell offTiny fruit yellowed and dropped after flowering

03 of 04

What happened The flowers were not pollinated well, so the little melons died instead of growing. Watermelon needs lots of bee visits, and seedless kinds need a seeded variety planted nearby.Poor pollination. The female flower was not adequately pollinated, so the young fruit aborts. Watermelon needs many bee visits per flower, and seedless types fail entirely without a seeded pollinizer nearby. Common in cool, wet, or pollinator-scarce conditions and during extreme heat. Next season Grow some flowers nearby for the bees, hand-pollinate early flowers if needed, and always plant a seeded watermelon next to any seedless ones.Plant flowers to draw bees, avoid spraying open blooms, hand-pollinate in the morning if set is poor, and always grow a seeded pollinizer alongside seedless types.

The melon rotted on its undersideMelon rotted on the bottom where it touched the soil

04 of 04

What happened The melon sat on wet ground and rotted on the bottom. Damp soil and poor drainage let rot soften the fruit where it touched the ground.Fruit rot, typically from a wet underside in prolonged contact with damp soil, favored by poorly drained, rainy conditions and the cucurbit fruit-rot fungi. A soft, sometimes molded patch develops where the melon sits. Next season Plant on raised hills so water drains away, and slip a board or straw under each melon so it is not on wet ground.Plant on raised hills for drainage, avoid low wet spots, and set each sizing melon on a board, tile, or thick mulch to lift it off the soil.

The usual suspects

Pests & diseases

Pests

Cucumber beetles

P · 01

Symptoms Small yellow beetles with stripes or spots chew on the leaves and flowers of young plants and can scar the fruit. They can also spread disease, though watermelon handles the wilt disease better than cucumbers or cantaloupe.Small striped or spotted yellow beetles chew young leaves, stems, flowers, and the rind of developing fruit, and can enter the soil to feed on seedlings below ground. The bigger threat is indirect: cucumber beetles can transmit bacterial wilt and spread mosaic viruses, though watermelon is far less prone to bacterial wilt collapse than cucumber and muskmelon. Cause Cucumber beetles spend the winter as adults and move onto young plants early. They feed on the leaves and can carry diseases from plant to plant, and seedlings are most at risk.Striped and spotted cucumber beetles feed on cucurbits and overwinter as adults, colonizing plants early in the season. They carry the bacterial wilt organism in their gut and spread mosaic viruses as they feed; seedlings are most vulnerable. Organic treatment Cover young plants with a light row cover (take it off when flowers open so bees can reach them), pick beetles off by hand, and clear away weeds. Yellow sticky traps help, and strong young plants shrug off some feeding.Protect seedlings with floating row cover removed at flowering for pollination, hand-pick beetles, and clear weeds that shelter them. Yellow sticky traps help monitor and reduce numbers; keep young plants vigorous so they grow past the most vulnerable stage. Prevention Cover seedlings until they flower, keep them growing strong, clear away weeds and old plants, and do not plant where melons or squash grew last year.Exclude beetles from seedlings with row cover, keep plants growing fast, clear weeds and debris, and rotate away from where cucurbits grew. Aim control at the early-season colonizers.

Aphids

P · 02

Symptoms Tiny soft insects gather under the leaves and on new growth, making leaves curl and yellow, often with a sticky film. They can also spread viruses that damage the plant.Colonies of small soft-bodied insects, often melon aphids, cluster on leaf undersides and growing tips, curling and yellowing the leaves and coating them in sticky honeydew that grows sooty mold. Beyond direct feeding, melon aphids transmit mosaic viruses that mottle and distort the foliage and can ruin a crop. Cause Aphids are small insects that suck the plant's juices and multiply quickly, especially on soft, over-fed growth. The sticky honeydew they leave grows black mold, and they can carry plant viruses.Melon and other aphids suck sap and multiply rapidly in warm weather, building up fast on stressed or over-fertilized plants, and typically colonize once the vines begin to run. The honeydew they excrete fosters sooty mold, and several species spread cucurbit mosaic viruses. Organic treatment Blast them off with a strong spray of water and treat the undersides of the leaves with insecticidal soap, repeating every few days. Ladybugs and other helpful insects eat aphids, so welcome them.Knock colonies off with a strong jet of water and spray insecticidal soap or horticultural oil with thorough coverage of leaf undersides, repeating every few days. Conserve ladybugs, lacewings, and parasitic wasps, which usually bring aphids under control; reflective mulch deters them from young plants. Prevention Do not over-fertilize with nitrogen, check the undersides of leaves regularly, and let helpful insects do their work. A reflective mulch around young plants helps keep aphids away.Avoid excess nitrogen, which drives the soft growth aphids favor, scout leaf undersides and growing tips, and support natural enemies rather than spraying broadly. Reflective or aluminum-foil mulch deters aphids from young plants.

Spider mites

P · 03

Symptoms The leaves get a fine yellow or bronze speckling, and in bad cases you see tiny webs underneath. Spider mites love hot, dry weather and can build up fast on watermelon in summer.Pale yellow and reddish-brown stippling appears on the upper sides of leaves, ranging from small specks to large whitish, stippled areas, and fine webbing shows on leaf undersides in bad infestations. Two-spotted spider mites explode in hot, dry weather, exactly watermelon's season, and heavy feeding bronzes and dries the foliage, cutting fruit size and sugar. Cause Tiny mites that thrive in hot, dry summers and multiply fast, especially after broad insecticide sprays kill the helpful bugs that normally keep them down. They feed on the undersides of the leaves.Two-spotted spider mites are tiny sap-feeders that proliferate during hot, dry weather and whose populations explode rapidly when their natural enemies are killed off by broad-spectrum sprays. They feed mostly on leaf undersides. Organic treatment Spray the plants, especially the undersides of the leaves, with a strong stream of water, and treat with insecticidal soap or horticultural oil if needed. Avoid spraying broad insecticides, which kill the good bugs that eat mites.Spray plants with a strong jet of water to dislodge mites and raise humidity, and apply insecticidal soap or horticultural oil with thorough leaf-underside coverage before populations peak, repeating as needed. Avoid broad-spectrum insecticides, which kill the predatory mites and insects that control them. Prevention Keep plants watered so they are not stressed in the heat, and avoid spraying strong insecticides that kill helpful bugs. Check under the leaves during hot, dry weather and treat early if you see speckling.Keep plants well watered and not heat-stressed, since drought-stressed plants are hit hardest, and avoid broad-spectrum insecticides that wipe out natural enemies. Scout leaf undersides through hot, dry spells and act early.

Squash bug

P · 04

Symptoms Leaves get yellow spots, then brown and wilt, and you find clusters of shield-shaped gray-brown bugs and their bronze eggs under the leaves. Watermelon is not their favorite, but they can still bother young plants.Leaves develop yellow specks that brown and wilt, and heavily fed runners can wilt and turn brittle. Flat bronze egg clusters appear on leaf undersides along the veins, and gray-brown adults and pale nymphs cluster near the crown and under debris. Watermelon is less affected than winter squash, but young plants can still be hurt. Cause Squash bugs pierce the leaves and stems and suck out the juices, which makes the vines wilt. They hide in plant debris over winter and prefer squash to watermelon, but can still attack young plants.The squash bug feeds with piercing-sucking mouthparts on cucurbit foliage and stems, injecting saliva that wilts and browns the tissue. There is one generation a year in much of the South, and adults overwinter in garden debris. It prefers squash and pumpkin to watermelon. Organic treatment Pick the bugs off by hand and scrape off the egg clusters under the leaves. A board laid on the ground overnight draws them underneath, then lift it in the morning and destroy them. Treat the young bugs with insecticidal soap.Hand-pick adults, crush the bronze egg masses on leaf undersides, and trap bugs by laying a board near the plants overnight, then lifting it in the morning and destroying the cluster underneath. Target young nymphs with insecticidal soap, since adults are tough to kill. Prevention Clean up old vines after harvest so the bugs have nowhere to overwinter, move your melons around the garden each year, and check under the leaves for eggs early in the season.Clean up vines and debris at season's end to cut overwintering sites, rotate cucurbits, and scout leaf undersides for the bronze egg clusters from early in the season, acting before nymphs mature.

Squash vine borer

P · 05

Symptoms On many squash, a healthy plant suddenly wilts in summer with sawdust-like specks at a hole near the base of the stem, and a fat white grub inside. Watermelon rarely gets this, since the borer mostly leaves it alone, but it is still worth a look.On susceptible squash a vine wilts suddenly in midsummer with sawdust-like frass oozing from a hole low on the stem and a fat white caterpillar inside. Watermelon is the fortunate exception: the borer rarely attacks watermelon or cucumber, so this collapse is uncommon, though heavy local pressure can occasionally produce damage. Cause A moth lays eggs at the base of squash stems in early summer and the grubs tunnel inside, but the moth strongly prefers thin-stemmed squash like zucchini and mostly leaves watermelon alone.The larva of the squash vine borer moth bores into thin-stemmed Cucurbita pepo squash; it largely avoids watermelon and cucumber, so watermelon planted near a borer-ravaged zucchini usually sails through untouched. Where pressure is severe, an occasional larva may still enter. Organic treatment Watermelon seldom needs treatment. If you do find a borer, slit the stem with a knife, dig out the grub, and cover the spot with damp soil so it can re-root.Rarely needed on watermelon. If a borer does enter, slit the stem lengthwise, remove the larva, and bury that node under moist soil to re-root; remove badly damaged vines. Prevention Growing watermelon is half the battle, since the borer mostly skips it. If borers are bad where you live, cover young plants with a light row cover until they flower, then take it off so bees can pollinate.Choosing watermelon is itself most of the prevention, since the borer mostly avoids it. Where pressure is severe, row cover from planting until flowering excludes the egg-laying moths, and tilling in late winter and rotating disrupts overwintering pupae.

Diseases

Anthracnose

D · 01

Symptoms Dark brown-black spots show up on the older leaves and grow into ragged patches, and the fruit can get sunken dark spots on the rind. In wet weather the spots may look pink-orange. Bad cases strip the leaves off the vine.Small brown-black spots appear first on the older crown leaves, expanding into ragged, sometimes water-soaked lesions; in damp weather the spots carry orange-pink spore masses that turn gray as it dries. On fruit it causes sunken, dark spots on the rind that can keep developing in transit and storage, and severe infection defoliates the vines. Cause A fungus that thrives in warm, wet weather and spreads from infected seed and old plant debris. It is worse on late plantings and in rainy spells.Anthracnose is caused by the seed-borne fungus Colletotrichum, favored by warm, damp weather and prolonged leaf wetness, and it hits late plantings especially hard. It overwinters on infected debris and seed. Organic treatment Treat early, at the first spots, with a labeled fungicide and remove badly affected leaves and fruit. Water the soil, not the leaves, and stay out of the patch when the vines are wet.Treat at the first spots with a labeled fungicide such as chlorothalonil or mancozeb, covering both leaf surfaces, and remove the worst-affected leaves and fruit. Avoid overhead watering and working among wet vines. Once it is widespread, control is mostly damage limitation. Prevention Choose resistant varieties and clean seed, rotate where you grow melons so they are not in the same spot every year, water at the base, and remove sick leaves and fruit early.Plant resistant varieties and disease-free seed, do not soak seed before planting, rotate watermelon and other cucurbits out of the bed for several years, water at the base, and start a protective spray schedule before the disease appears in wet seasons.

Gummy stem blight

D · 02

Symptoms You see round black spots on the leaves and dark sunken patches on the stems, sometimes with a brown gummy ooze. The leaf spots grow fast into big tan blotches, and in warm, wet weather the vines can collapse.Round, black, wrinkled spots form on young leaves and dark, sunken, sometimes girdling lesions develop on the stems, often with a brown gummy ooze on the surface. Brownish circular leaf spots expand rapidly into large tan lesions, and a brown streak can appear at the blossom end of the fruit. In warm, wet weather the foliage and vines can collapse quickly. Cause A fungus that spreads in warm, wet weather, especially in the South, and survives on seed and old plant debris. Long rainy spells make it move fast.Gummy stem blight is caused by the seed-borne fungus Didymella bryoniae (Stagonosporopsis), a warm-weather, southern cucurbit disease driven by prolonged rainy periods and leaf wetness. It survives on seed and infected debris. Organic treatment Use a labeled fungicide at the first sign and remove the worst vines. Give plants room so air moves between them, and water at the base to keep the leaves dry.Start a protective fungicide schedule at the first sign, covering leaf undersides, and remove and destroy badly affected vines. Improve airflow, avoid overhead irrigation, and keep the foliage as dry as possible. Prevention Pick resistant varieties and clean seed, rotate where you grow melons, give plants room, water at the base, and keep an eye out in warm, humid weather.Plant resistant varieties and clean seed, rotate cucurbits out of the bed for several years, space plants for airflow, water at the soil line, and avoid working among wet vines. Scout closely in warm, humid weather.

Fusarium wilt

D · 03

Symptoms The leaves turn yellow and wilt, often on just one runner at first, and the plant dies even though the soil is wet. You may see a pinkish mold near the base of a dying stem. It is the most serious soil disease of watermelon.Foliage turns yellow and wilts, often starting on one side or one runner, and infected plants decline and die soon after symptoms appear even though the soil is moist. A pinkish-white cottony growth can show near the soil line on dying stems, and a cut stem reveals browned, discolored vascular tissue. It is the most damaging soilborne disease of watermelon. Cause A soil fungus that only attacks watermelon, blocking the plant's water pipes so it wilts. It builds up in warm, sandy soil and survives for years, which is why long rotations matter.Fusarium wilt is caused by the soilborne fungus Fusarium oxysporum f. sp. niveum, which is specific to watermelon and clogs the water-conducting tissue. It thrives in warm, sandy soils typical of watermelon ground and persists in soil for many years; several races exist, and resistance covers only some of them. Organic treatment There is no cure once a plant has it, so pull and destroy infected plants. You cannot spray it away, so prevention is everything.There is no cure once a plant is infected; remove and destroy wilting plants. Management is preventive and cultural, since fungicides do not control a soilborne vascular wilt. Prevention Choose resistant varieties, do not grow watermelon in the same ground for at least five years, and where the disease is bad, look into grafted plants on resistant roots. Keep plants healthy and do not overwater.Plant resistant varieties, follow a long rotation of at least five years out of watermelon and related cucurbits, and consider grafting onto resistant rootstock where the disease is established. Avoid moving infested soil, and keep plants vigorous but not over-watered.

Powdery mildew

D · 04

Symptoms A white, powdery coating spreads over the leaves until they yellow, brown, and die. The plant fades early, and the melons may not size up or sweeten well.White, powdery patches appear on the upper and lower leaf surfaces and stems, spreading until leaves yellow, brown, and die back ahead of schedule. Early defoliation cuts the season short, reduces fruit size and sugar, and exposes melons to sunscald. Cause A fungus that spreads on warm, humid days, especially where plants are crowded and air does not move well. It does not need wet leaves to take hold.Powdery mildew fungi thrive in warm conditions with high humidity but do not need leaf wetness, spreading by wind-blown spores. Crowded plantings, poor airflow, and shade worsen it, and it is a common late-season cucurbit disease. Organic treatment Treat early, at the first white spots, with a labeled fungicide like sulfur or horticultural oil, and remove badly affected leaves. Water the soil, not the leaves.Treat at the first spots with a labeled fungicide such as sulfur or a horticultural oil or biofungicide, covering both leaf surfaces, and remove the worst leaves. Avoid overhead watering. Once it is widespread, control is mostly damage limitation. Prevention Pick resistant varieties, give plants plenty of room and full sun, water at the base, and start checking in midsummer, treating the first white spots early.Choose resistant varieties, space plants for airflow, plant in full sun, and avoid excess nitrogen and overhead watering. Scout from midsummer and treat at the first sign.

Downy mildew

D · 05

Symptoms Yellow, angular patches show on top of the leaves with fuzzy gray-purple growth underneath, mostly in damp, humid weather. The spots brown and spread, and badly hit leaves can die within a couple of weeks.Small yellowish, angular areas bounded by the leaf veins appear on the upper leaf surface, water-soaked underneath with a grayish or purplish fuzzy spore growth in humid weather. Lesions turn from yellow to brown and several infected leaves can die within 10 to 14 days, rapidly defoliating the vines. Cause A mold-like disease that blows in on the wind during mild, rainy weather and needs wet leaves to infect. It can move through a planting quickly.Downy mildew is caused by the air-borne, fungus-like water mold Pseudoperonospora cubensis, which needs leaf wetness and humidity to infect and arrives on wind currents during mild, rainy stretches, often spreading north through the season from overwintering sites in the far South. Organic treatment Open up the planting so leaves dry faster, remove the worst leaves, and use a labeled fungicide when wet weather sets in. Do not water over the leaves.Improve airflow, let foliage dry, remove badly affected leaves, and apply a labeled fungicide covering leaf undersides when conditions favor the disease. Avoid overhead irrigation, which keeps leaves wet. Prevention Give plants room so air moves between them, water at the base, choose resistant varieties if downy mildew is common where you live, and watch closely in humid weather.Space for airflow, water at the soil line rather than overhead, choose resistant varieties where available, and start protective sprays when the disease is reported moving into your area. Scout closely in humid weather.

Verified · 4 sources View

Seasoned

Where to plant next year

Crop rotation

Try not to grow watermelon or its relatives (cucumbers, melons, squash) in the same spot more than once every 3 years, and wait longer, up to five years, if you have had wilt or anthracnose. Moving them around the garden is the best way to avoid a buildup of disease. Clean up old vines at the end of the season too.Rotate watermelon and its cucurbit relatives on at least a 3 year cycle, and stretch it to five years where Fusarium wilt or anthracnose are established, since the watermelon wilt fungus persists in soil for years and anthracnose and gummy stem blight carry over on debris and seed. A long rotation is the single most important cultural defense against the diseases that limit this crop. Clear and remove spent vines at season's end rather than tilling them in, which removes overwintering disease sites.

Family

Cucurbitaceae

Years between

3 years

in the same bed

Avoid following

Do not plant watermelon where you grew cucumbers, melons, squash, or pumpkins in the last few years. They get the same pests and diseases, which build up in the soil.Avoid planting watermelon where any cucurbit grew in the last few years, including cucumber, muskmelon, squash, and pumpkin. They share cucumber beetle, the mildews, and especially the soilborne Fusarium wilt and seed- and debris-borne anthracnose and gummy stem blight, which build up in the soil and on residue.

Plant after

Legumes such as beans and peas, sweet corn, leafy greens, or alliums like onions and garlic make good preceding crops, since they do not share the cucurbit pest and disease complex, and a legume leaves a little nitrogen behind.

Verified · 2 sources View

Read the full methodology →

Spot a data point that doesn't match your experience? Submit a correction; accepted corrections earn full author credit on the page.

Watermelon

What's happening right now

Planting calendar

Seed to garden

The growing journey

Your soil

Identify yours

What this crop wants

If your soil doesn't match

Containers and raised beds

Care guide

Soil pH for watermelon

Watering

Feeding

Companion planting

When to pick

What to expect

Recommended varieties

Storing your harvest

Common problems

Pests & diseases

Crop rotation

When plant taps you on the shoulder

Common questions

Got a question we missed?

Share a tip

Report a problem

Methodology & sources

Growing notes, weekly.