How To Grow Watermelon (Detailed Instructions)

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Almost everything homegrown in the garden tastes better than its grocery store counterpart, but watermelon might take the cake as the most improved. It’s packed full of so much more juicy, layered flavor than anything you can grab at a supermarket—you don’t know watermelon until you bite into your own homegrown melon that’s still warm from the sun!

The great news: watermelon is relatively easy to grow! It takes a long season and thrives in hot weather, but give it some space to sprawl, and it’s mostly maintenance-free! Let’s get you growing some melons.

Table of Contents

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• Are watermelon easy to grow?
• When should I plant watermelon?
• How long does it take for a watermelon to grow to full size?
• What watermelon varieties should I grow?
• Should I grow watermelon from seeds or plants?
• How do I grow watermelon from seed?
• How do you prepare soil for watermelon?
• How do I transplant watermelon seedlings?
• Do watermelon plants need a lot of sun?
• What temperature do watermelons grow in?
• Do watermelons need lots of water?
• What can you plant next to watermelon?
• How do you grow a watermelon vertically?
• Do I need to fertilize my watermelon plants?
• Should I cut back watermelon vines?
• Do I need to rotate my crop?
• How do you tell if a watermelon is sweet or ripe?
• How do you harvest watermelon?
• How many watermelon will one plant produce?
• Do watermelon plants come back every year?
• What about growing seedless watermelons?
• Troubleshooting

Are watermelon easy to grow?

If you can grow a cucumber or a zucchini, you can grow a watermelon! Watermelon plants are remarkably prolific, and as long as your climate is hot enough (or you can fake it with poly tunnels or cold frames), watermelons are a breeze to get going.

When should I plant watermelon?

Watermelon requires a relatively long growing season (about 80-90 days from sowing the seeds), and it wants absolutely nothing to do with cool weather. Plant your watermelon when the soil has warmed to around 70ºF and there are no longer any cool nights in the forecast. For many people, this is actually two to three weeks after their last frost date in the spring.

How long does it take for a watermelon to grow to full size?

Watermelons require 80-90 days from seed sowing to grow a full-size watermelon. Some smaller-sized watermelons (like Sugar Baby) can reach maturity in closer to 70 days.

What watermelon varieties should I grow?

The fun thing about growing watermelon is that there are so many options beyond the standard red watermelon you see at your grocery store—you can grow yellow, orange, and even white-flesh watermelon! These are some of our favorite varieties:

• Moon and Stars—This legendary heirloom watermelon is named for the interesting markings on its rind. Melons can grow up to 40 pounds each!
• Sugar Baby—This small-sized seeded watermelon lives up to its name. It is so sweet, you’ll swear someone sprinkled sugar on it! The melons are about 10″ across, and you can get as many as 4-6 per watermelon vine. There is also Sugar Baby Bush, which is the same watermelon but grown on a patio-friendly plant with a bush habitat.
• Orangeglo Watermelon—Many orange and yellow watermelon varieties are fun to look at, but don’t offer much in the way of flavor, but not Orangeglo!
• Blacktail Mountain—For those of you with shorter, cooler summers, Blacktail Mountain might be a good option for you. It’s an early ripener (taking only about 70 days for a full size watermelon) with great flavor.

Should I grow watermelon from seeds or plants?

Like all cucurbits, watermelon prefers to stay put and not be transplanted. In most climates, you’ll do best to directly sow watermelon seeds in warm soil in the bed they will grow in.

We did an experiment in the Growfully Garden a few years back testing transplanted cucurbits versus direct sown, and it only took three weeks for all of our direct sown plants to catch up to our transplants that we started 6 weeks earlier!

If you live in a cooler climate (or just want to ensure germination), you can start your watermelon seeds indoors, but we do recommend you do so using a seed starting method that will not disturb the roots during transplanting. Newspaper pots or soil blocking are both good options.

How do I grow watermelon from seed?

You’ll have a hard time tracking down watermelon seedlings at a garden center because watermelon plants perform so well from seed! So grab yourself a seed packet, and let’s get growing.

How to Sow Seeds Directly in the Garden (RECOMMENDED)

1. Amend your soil with at least 1-2 inches of compost before planting your watermelon seeds.
2. 7-14 days after your last frost date, sow seeds 1/2″ deep in the soil in small hills or rows spaced 36″ apart. In the hills, plant 6-8 seeds; in the rows, plant 2-3 seeds every 36″.
3. Once the seedlings have started to grow and the true leaves are formed (not the initial leaves that came up with the seedling), use small snips to thin the seedlings to 2-3 per hill or one plant every 36″ in a row.

How to start watermelon seedlings indoors (only recommended for cooler climates or to ensure germination)

1. Fill a large seedling pot or soil block with seed starting medium. We like to use coco coir (4 parts), vermiculite (2 parts), and perlite (1 part).
2. Sow 2-3 seeds in each pot (this will ensure germination of at least one), about 1/2″ deep in the pot.
3. Gently water the seeds (a mist or spray bottle is great for this!), and keep the soil evenly moist until germination.
4. Keep the seeds somewhere warm, ideally where the soil can stay between 75-85°F. You’ll probably need a heat mat to achieve this temperature. You’ll see seedlings popping up within 7-10 days.
5. Once you see the first set of true leaves (these are the leaves that look like melon leaves, not the initial leaves that came up when the seed first germinated), use small snips to clip off all but the strongest seedling in each pot.
6. 7-14 days after your last frost date, plant the watermelon seedlings 36″ apart in the garden.

How do you prepare soil for watermelon?

The most important thing to remember when preparing your soil for watermelon plants is that they need the soil to be very warm to grow. Soil needs to warm to at least 70°F before watermelon plants can thrive.

Growfully Protip

Having a hard time getting your soil warm enough for watermelons? Row covers, cold frames, or even just a layer of thick black plastic can warm up soil quickly by trapping warm air near the soil surface.

Watermelon plants prefer a soil pH of between 6.0-7.5—this range covers the vast majority of garden soils, but if you need to amend your soil to adjust pH, do so before planting.

Watermelons are heavy feeders, so you want to make sure you plant them in nutrient-rich soil to ensure they can produce lots of delicious melons. We recommend amending your bed with at least 1-2″ of well-rotted, rich compost or manure before planting. You can also amend your soil with a balanced, slow-release organic fertilizer.

Growfully Protip

Mulch is very important for watermelon plants to help retain moisture, reduce weed competition, and give cushion for the melons to grow on. We like a base of cardboard (to really stamp out weeds), topped with either weed-free straw or pine shavings.

How do I transplant watermelon seedlings?

Like we mentioned above, we don’t recommend doing watermelon transplants for most folks, but if you are transplanting watermelon seedlings, the key is to disturb the roots as little as possible.

1. Make sure you have properly hardened off your seedlings to acclimate them to the weather. Ensure that your soil temperature is 70ºF or above.
2. Transplant on a warm but not hot day that is preferably overcast with calm winds.
3. Water your watermelon seedlings thoroughly about an hour before you plan on transplanting them.
4. If using a plantable seed starting method (like newspaper pots, peat pots, or soil blocks), plant the seedling directly into the soil. You might want to (gently!) tear off the bottom of the newspaper pot or peat pot to encourage root growth.
5. Water the plants in well.
6. Don’t be surprised if your plants go through a bit of transplant shock—yellowing, drooping of leaves, or stunted growth. With a little TLC, they’ll bounce back and take off soon.

Do watermelon plants need a lot of sun?

Yes! Watermelon plants require full sun (8 to 10 hours daily) to produce melons.

What temperature do watermelons grow in?

Watermelons like it moderately hot, and they grow their best between 75°F and 95°F air temperature.

Do watermelons need lots of water?

Just like most other plants in your veggie garden, watermelons need 1 to 2 inches of water per week to grow adequately. This is particularly important when the watermelon plants are setting and growing fruit. A watermelon is made up of 92% water—if you want big, juicy watermelons, make sure your plants stay well watered!

Growfully Protip

The sprawling vines and large canopy of leaves of a watermelon vine can act like a mulch to help retain soil moisture and prevent weed competition around your watermelon plants.

What can you plant next to watermelon?

The most important companion plant for watermelon are plants that can repel pests (like squash bugs or cucumber beetles) and can also attract beneficial pollinators that can help ensure your watermelon plant is pollinated and can set fruit.