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Summer is for watermelons—here’s how to grow your own

Grow juicy melons in your backyard

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Growing watermelons means you get to eat sun-warmed, sweet, juicy fruit straight off the vine—a top-tier garden delight.

Guess what? It’s not hard to grow watermelons. With a little attention to space, soil, and temperatures, you can grow great watermelons in any yard—or even in raised beds.

Read on for how to grow a watermelon.

How long does it take to grow a watermelon?

Two packets of Watermelon Sugar Baby Citrullus Lanatus seeds.
Credit: Reviewed / Gaea's Blessing

Watermelon growth time depends on the variety. Sugar Baby mature around the 80-day mark.

Watermelons are hot weather plants and therefore cannot tolerate cold temperatures. Plant watermelons after the last frost of spring, but early enough so they have time to ripen before the first frost of fall.

Most varieties of watermelon need to grow for at least 80 to 100 days after seedlings are planted outside to bear ripe melons. Small, round varieties of watermelons like Sugar Baby, which ranges in size from eight to 10 pounds, mature around the 80-day mark. Bigger, longer varieties, like Jubilee or Allsweet, which can grow up to 25 pounds, take about 100 days.

In short, the time between the last spring frost and the first fall freeze is your growing season, also called the frost-free season. You can find the average last frost date for your region using NOAA maps or search your zip code in the The Farmer’s Almanac database. Just remember that “average” isn’t an exact date.

To extend your planting season, start growing watermelon seeds indoors 2-4 weeks before your last frost date or buy seedlings. Watermelon seeds can be sowed in the ground, too, if your growing season is long enough.

How to grow a watermelon

Prep the soil with organic nutrients

A flier for MySoil soil test kit is laid out next to a cell phone screen showing bar graph results for a sample vegetable garden.
Credit: Reviewed / MySoil

Use a soil test kit to make sure your soil’s pH is just right.

Watermelons grow best in sandy loam soils that drain well with a pH between 6 and 6.5. You can check your soil’s pH with a soil test kit. If your garden soil tends to drain slowly, consider building a raised bed and filling it with a mix of soil, sand for drainage and well-rotted manure or compost.

Make sure the soil is warm enough

Two Taylor soil thermometers, one large and one small.
Credit: Reviewed / Taylor Precision Products

A soil thermometer helps you make sure seeds are warm enough to germinate.

Watermelons like it hot. Seeds won’t germinate if the soil temperature is below 60°F, and they’d prefer it if your was 70°F. If you’re starting seedlings inside, consider using a heat mat to keep them toasty.

If you’re not sure how warm your soil is, take its temperature. You can use a meat thermometer to measure the temperature in your soil if it goes down to 50°F or get a soil thermometer.

Get the Taylor Precision Products Soil Testing Thermometer on Amazon for $11

Sow seeds far apart

Two Burpee SuperSeed pop-out reusable seed starting trays are arrayed side by side.
Credit: Reviewed / Burpee

Pop-out seed starting trays give watermelon seedlings a home before you plant them outdoors.

Watermelons grow on vines 3-4 feet long, while vines for larger watermelons may need to sprawl 10-feet or more.

Short on space? You can grow watermelons on a low, sturdy trellis like an A-frame design that can also be used to grow cucumber. Plant watermelon seeds roughly a half-inch deep in the soil. If you’re planting watermelon seedlings, remove the plastic pot and plant them as deep in the soil as they were in the pot; don’t mound dirt higher on the stem. If you’re planting your watermelons in a row, place two to three seeds together about 2 feet apart, and space the rows at least 5 feet to 6 feet apart.

You can also plant watermelon seeds on hills in mounds of dirt that are about four to eight inches high, about a foot wide, and four- to five-feet apart. Count on six seeds per hill. A few weeks after planting, when the plants have two or three leaves, thin them to two plants per hill.

Support melons growing on a trellis by putting a sling or support underneath and attaching it directly to the trellis—not another part of the vine. You can use old stockings or onion bags, or get a pack of melon hammock netting to keep your little watermelons growing safely.

Watering watermelons

The Orbit B-hyve Smart Hose Faucet Timer, a cellphone and Wi-Fi hub.
Credit: Reviewed / Orbit

App-connected smart hose faucet timers help control the watering of your plants remotely.

Watermelons need plenty of water to thrive. Once settled in the soil, make sure the melon gets one to two inches of water per week—about a half hour at a time. Use a rain gauge to check how much water your watermelon plants are getting.

It’s better to water them in one long, slow session each week instead of daily doses. The water will soak deeper into the soil where the roots are, and the leaves will stay drier longer. Water in the early morning so the leaves can dry out in the sun. Watermelon plants tend to get diseases if their leaves get wet.

If you’re going on vacation but want to keep your garden growing, try an app-connected smart hose timer. The timer attaches to a garden hose, which can be connected to a drip irrigation system or a sprinkler head for remote water management. If you have an in-ground irrigation system, a smart sprinkler controller effectively works the same as a hose timer, allowing you to set watering schedules, turn the sprinklers on/off, and overall remotely control your sprinkler system. Smart lawn watering devices save you time, money, and prevent overwatering.

About two weeks before you expect your watermelons to ripen, stop watering them. Too much water just before harvest time can lead to watermelon splitting open while it’s still on the vine—and you don’t want to share your harvest with wasps and slugs. Unless your region is going through a drought, turn off the hose.

How to harvest watermelons

Two gray and black pruning gloves beside a pair of gardening shears.
Credit: Reviewed / SHOWA / Gonicc

Be sure to use gardening gloves and pruning shears when cutting watermelons free from the vine.

Unlike cantaloupes, watermelons don’t “slip” (fall off the vine) when they’re ripe. Instead, look for these signs your watermelon is ready to pick:

  • The “ground spot” where the melon sits on the soil turns yellow.
  • The vine tendrils near the fruit dry up and turn brown.
  • The watermelon’s skin looks less shiny, with more of a matte/dull appearance

Put on your gardening gloves and use a pair of pruning shears to cut the watermelon free from the vine. Don’t delay! Watermelons will rot if you leave them on the ground—and plenty of pests enjoy ripe watermelons, including coyotes.

Eat your watermelon immediately, or pop it in the fridge for up to two weeks.

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