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How To Grow The Sweetest Watermelon From Seed (3 Delicious Varieties)

Memorial Day weekend is the unofficial kickoff to the summer season, and nothing says summer like biting into fresh, juicy watermelon straight from the garden. Of course, you can buy a watermelon at the grocery store, but once you’ve had a homegrown melon you’ll never want to go back to store bought.

A surprising number of people think that you can only grow watermelon in the South, but Northern gardeners can enjoy homegrown watermelon too! They’ll just need to tweak the growing process just a tad to make sure that their melons ripen before the end of the season.

In this blog post, we will guide you, step-by-step, through the process of growing watermelons from seed and recommend some of our sweetest varieties. Wherever you garden, you can wow your family and friends by bringing homegrown watermelon to the next cookout or backyard barbeque!

Starting watermelon seeds

How you start watermelon seeds will depend in part on where you live. Southern gardeners with longer, hotter summers can start watermelon seeds outdoors after the last frost, but Northern growers may opt to start their seeds indoors to get a jumpstart on the growing season.

Sow indoors

You can start watermelon seeds indoors, but it isn’t necessary unless you have a shorter growing season. Growers in the South can direct sow watermelon seeds about a week after the last frost, or when soil temperatures reach 70°F (21°C).

The best time to start your watermelon seeds indoors is in the late winter, about six weeks before the last frost. Watermelon seedlings grow quickly, so seeds started indoors may need to be bumped up into pots before they go into their permanent home outside. Alternatively, you can sow watermelon seeds in four-inch pots and skip the bumping-up step. Mature watermelon seedlings can be transplanted outside one week after the last frost date.

Direct sow

Whether you plan to start watermelon seeds indoors or direct sow the seeds outside, you’ll first need to prep the soil for planting. Watermelon plants benefit from a practice called mounding, or planting into small hills. Mounds are doubly beneficial: the mounds warm up faster and drain much better than the surrounding soil.

Most growers sow watermelon seeds directly in the ground a week or two after their last frost date. Sow four watermelon seeds per mound—once the seeds sprout, you’ll thin the seedlings back to the strongest two vines. Most watermelon vines can reach up to 20 feet in length, so space mounds four to six feet apart to allow for the mature plants to sprawl.

Growing requirements for watermelon

  • Full sun

Watermelons need full sun to produce their deliciously sweet fruit, so choose a planting location that gets eight hours of sunlight a day, minimum.

  • Fertile, well-draining soil

The soil should be well-draining and fertile, and the pH level will ideally fall between 6.0 and 6.8. Watermelon plants are heavy feeders, so add a generous layer of organic compost and work it into the soil, along with a balanced granular fertilizer.

  • 1–2 inches of water per week

As you might expect, watermelons require a lot of water throughout the growing season, so installing drip irrigation or a sprinkler system is a must. Otherwise, you’ll spend a good amount of time dragging water hoses around. Make sure that watermelons get at least one inch, ideally two inches, of water per week.

  • Ample space 

By nature, watermelons are vining plants that have a tendency to sprawl and take over the garden. Either plant watermelon at the edges of the garden, so the vines don’t smother your other crops, or train the vines to grow vertically on a trellis. You can tie rags or pieces of netting underneath young fruit to provide support as the fruit grows.

  • Pruning 

Pruning watermelon plants properly can lead to larger and sweeter melons. Once the plant has set three to four fruits, remove all other flowers and fruit that form later. While it might be scary at first, trust the process and once you make the cut, you’ll be rewarded with a better harvest. 

  • Pollination 

Watermelon plants produce both male and female flowers, but pollinators like bees and flies are essential to fruit development. Intercrop watermelon plants with flowers and native plants to attract beneficial insects to the garden, and if you don’t see many insects on your plants you can always hand-pollinate the flowers to ensure a good harvest.

For best results, feed watermelon plants with a phosphorus-potassium fertilizer when the plants begin flowering to encourage better fruiting. You’ll also want to stop irrigating watermelons two weeks before you plan to harvest so that the plants will concentrate their sugars and produce sweeter melons.

The 7 best-tasting watermelon varieties

There are hundreds of watermelons in the world, but there are a few that stand out from the rest. Shop our entire collection of non-GMO watermelon seeds here.

1. Sugar Baby

Our most compact watermelon, Sugar Baby, is an early icebox variety and a favorite among our customers. The small round fruits mature at 75 days and only weigh between six and ten pounds—perfect for one or two people. The juicy, red-orange fruit has few seeds and is resistant to watermelon fruit blotch.

2. Crimson Sweet

Hands-down the best melon to bring to a family function. The large, slightly oblong fruits are deliciously sweet and have very few seeds. Crimson Sweet is fairly disease-resistant and grows well in northern climates.

3. Cal Sweet Bush

Another bushy watermelon variety, Cal Sweet Bush is our go-to for containers. Compact and productive vines produce 2–3 symmetrical 10–12 pound fruits per vine for an abundant harvest, even with minimal space.

4. Congo

If you’re looking to feed a lot of folks, Congo is the variety for you. An heirloom variety and AAS winner, Congo produces oblong fruits with an average size of 35 pounds! To be so large, Congo is still a super-sweet variety that will thrill any taste-testers.

5. Charleston Grey

While it may not look like any watermelon you’ve ever seen, Charleston Grey still has that crisp texture and super sweet taste that makes for an excellent melon. One of the later varieties to mature at 85 days, Charleston Gray has excellent disease resistance and is worth the space it takes up in the garden.

6. Yellow Buttercup

Ever had a yellow-fleshed watermelon? Once you try Yellow Buttercup for the first time, you’ll be obsessed! The lemon-colored, seedless flesh is as sweet and crispy as any red melon but adds uniqueness to any party or cookout.

7. Secretariat Seedless

If you don’t want to fool with watermelon seeds, you’ll love Secretariat Seedless. An early-maturing variety that is harvestable at 80 days, Secretariat Seedless produces large 16 to 18-pound seedless fruits with crisp, bright red flesh.

How to tell when a watermelon is ripe

If you’ve ever bought a watermelon before, you know it can be a little tricky to pick out the perfect melon. Fortunately, there are three easy tests that you can use to determine if a melon is ready for harvest:

  • Does it make a hollow sound when thumped? A deep thunking sound is indicative of ripe melon.
  • Does it have a yellow field spot? Field spots form at the point where a melon rests on the ground. A yellow field spot has sat in the garden for longer than a white field spot, so it will indicate that the melon is ripe.
  • Is the tail brown? If the piece of stem that attaches the melon to the vine—growers call this the tail—is brown, the watermelon is ripe.

A perfectly ripe watermelon will be uniform in size and will feel very heavy, while an elongated melon is the result of irregular watering, and may taste bland. A shiny melon hasn’t had time to ripen, so only pick fruit that has skin on the duller side. Webbing, or the scarring near the field spot, is a result of pollination, so more webbing means that the melon received ample pollination.

Watermelons are ready to harvest when the fruit is ripe and sounds hollow when tapped. The bottom of the fruit should have a yellow spot, and the stem should be dry. Unlike other fruits that ripen off the vine (tomatoes, peppers, peaches, etc,), watermelons do not ripen off the vine, so wait until the fruit is ripe before picking it.

Once the fruit is ripe, harvesting watermelon is simple—use a sharp knife or garden shears to cut the melon from the stem, leaving a couple of inches of tail. Unlike squash or onions, watermelons don’t need to cure—go ahead and cut into it and enjoy the sweet, crisp taste of summertime. An uncut watermelon will store for two weeks in the refrigerator but once cut, the fruit will only keep for three to five days—if it lasts that long!

Growing watermelon from seed is a rewarding experience for young and old gardeners alike, and there’s no reason that you can’t grow your own melons this year! 

As long as you plant watermelons in fertile, well-draining soil and provide the plants with adequate sun and water, you’re sure to have an abundant harvest of fresh, sweet watermelons that you’ll be able to share with friends and family this summer.

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