In this article: Learn how to grow watermelon in your vegetable garden, plus how to start from seed and when to harvest.
Watermelon is one of my favorite fruits to grow in my garden. With 6 kids, fruit gets eaten fast! So the more we can grow the less we have to buy.
Who doesn’t love a nice cold watermelon on a hot summer day? And like many homegrown fruits and veggies, nothing tastes better than one picked fresh from the garden.
Watermelons are in the cucurbit family along with squash, cucumbers, and pumpkins.
Watermelons aren’t a difficult crop to grow, so if you have the space I highly recommend learning how to grow this rewarding fruit.
How to Grow Watermelon from Seed
You can direct sow your watermelon seeds directly into the garden after all danger of frost as passed and the soil is warm, but I prefer to start my seeds indoors 2-3 weeks ahead of time so that I can control the germination better.
To start seeds, fill your containers with seed starting mix and place the watermelon seed about 1 inch under the soil. Water well initially and keep the soil damp but not wet.
Watermelon seedlings sprout and grow quickly, making them very susceptible to becoming root bound in small containers. You can plant your watermelon in peat pots that allow the roots to push through and can be planted directly in the garden. Keep your seedlings in a sunny location (even outside is good if the weather is warm) or under lights to keep them from getting long and leggy.
When your watermelon seedlings are a couple of inches high and have at least one set of true leaves then can be planted out into the garden.
Carefully break apart of the roots if they are root bound and plant the watermelon plants directly into the garden with lots of organic matter. Don’t plant the plants too deep- match the soil level in the garden to the soil level of the plants in the pots.
Like I said, you can also direct sow seeds into the garden. To do this, simply place the seed about 1 inch (or as deep as the seed is long) under the soil.
Be sure to water well and don’t let them dry out to get a better germination rate. Also be on the lookout for pests that might eat your seeds!
Watermelon Varieties to Grow in Your Garden
There are 2 general types of watermelons: Seedless and Seeded. I will tell you now that growing seedless watermelons can be hard to do- even varieties that are said to be seedless don’t always end up that way in the garden.
Growing Seedless Watermelon Varieties:
Seedless watermelons haven’t been around all that long. Through years of breeding and crossbreeding watermelon growers have been able to create hybrids (not genetically modified).
These hybrids are just a sweet and have the same growth needs as seeded varieties.
Seedless watermelons are very popular since, of course, they don’t have seeds to deal with while cutting and eating.
Growing Seeded Watermelon Varieties:
Though the convenience of seedless watermelons is nice, I much prefer growing seeded varieties. Seeded watermelons are a bit easier to grow, you have more choices, they grow biggers and you can get heirloom varieties from which to save seeds.
And who doesn’t enjoy a good watermelon seed spitting contest?
Watermelon Varieties We Love:
Charleston Gray- These plants give lots of fruits. The flesh is smooth and sweet.
Carolina Cross- This variety holds the record for the largest watermelon, with fruits reaching up to 200 lbs. We grow them for the fair, but they are also one of our favorites to eat.
Orangeglo- Sweet orange flesh that is so good to eat! They are a staple in our watermelon patch- melons can get quite large.
Moon and Stars- This variety comes in both red flesh and yellow flesh. Both are equally as yummy! Can get up to 40 lbs.
Kolb’s Gem- My son grows these large fruits for the fair, but they are so sweet! Ours get over 60 lbs!
Jubilee- Long. large fruits. Deep red flesh that’s very sweet.
You will notice that most, or all of these, are large watermelons. There are quite a few of small or icebox watermelon types, but I feel like the amount of seeds to fruit make them not quite worth the effort.
How to Grow Watermelon: Care
Before you plant your watermelon seeds or seedlings in the garden you need to prepare your soil first.
Growing watermelon does require a lot of room. There are some bush varieties and you can grow watermelon vertically, though it takes a little more thought and planning- and usually involves creating hammocks for the fruits.
For the most part you need plenty of room to allow the watermelon vines to sprawl. I plant mine on black plastic since it helps warm the soil, preserve water, and keep the weeds down around the base of the vines. Black plastic is also helpful if you have a shorter growing season. You can use floating row covers and plastic together to extend your season, allowing you the long growing season watermelon requires.
Make sure that your soil is amended with plenty of organic material. Watermelon’s are heavy feeders and will grow better and taste sweeter in nice, rich soil.
Related Reading: 8 Ways to Improve Your Soil for Free
Watermelons thrive in heat and they need full sun- at least 8 hours per day. Soil temperatures should be at least 70 degrees, so don’t jump the gun and plant them too soon or they will just sit stunted until the weather has sufficiently warmed.
Watermelon plants have deep roots, so if you use mulch you won’t have to water them too much unless you are in a dry or drought prone area. When you do water, water deeply from the base of the plant and water early in the morning or in the evening.
If you are using row covers for warmth or pest control, you need to remove them when the vines start to flower. Your watermelon plants will produce both male flowers and female flowers, and they need pollinators to pollinate the flowers if the female flowers are to produce any fruit.
Try growing herbs, nasturtium or marigold around your watermelon plants to attract beneficial insects and pollinators.
Pests and Diseases Affecting Your Watermelon Plants
First and foremost, as I said above, healthy plants start with healthy soil. Healthy plants will have a much easier time fighting off both disease and pests. That said, here are some of the problems you might face with your squash plants:
Cucumber Beetles: Yes, we are talking about watermelon, but since cucumbers and watermelon are both cucurbits, many of the pests will attack all types of vines.
Cucumber beetles are small yellow and black beetles, either striped or spotted.
Some types of cucumber beetles will lay eggs in the soil and the larvae will eat on the roots of your plant. All types will feed on the plant and carry disease, so it’s best to control them.
Read: How to Control Cucumber Beetles Organically for tips on getting rid of this pest.
Aphids: Aphids can cause problems for a lot of garden crops, watermelons included.
Aphids have many predatory insects that can effectively control them- ladybugs being the most common.
Use companion plants such as nasturtiums to help with aphids and other flowers to attract beneficial insects.
Cucumber Mosaic Virus: Again because cucumbers and watermelons are in the same family, they are susceptible to the same pests and diseases.
Cucumber mosaic virus will cause your plants to be stunted, the foliage will be yellowed and curled. The flowers and fruits will be deformed and the fruits small and misshapen.
Controlling aphids can help control this virus, as they transmit the virus. Make sure your tools are clean to prevent transmission too.
Powdery Mildew: Powdery Mildew is a fungal disease that can attack your watermelons plants and overwinter in your soil year after year.
Powdery mildew looks like fuzzy, white spots covering the leaves of your plant. It can quickly spread through your entire melon patch if you don’t stop it in time.
It thrives in crowded, low light, high humidity locations- so not crowding your plants can help prevent it in your garden.
Read Controlling or Eliminating Powdery Mildew for some information on this disease.
Controlling pests can go a long way in controlling melon disease as well. Cucumber beetles can carry bacterial wilt and cucumber mosaic virus. Whitefly can introduce disease that stunts growth and causes poor flavor in the fruit.
While watermelons are less susceptible, if they don’t have enough squash to feed on squash bugs may attack your watermelon vines.
When to Harvest Watermelon
How long does it take watermelon to grow? It will depend greatly on the variety you choose but the average time to harvest is about 80 days.
You can find some early watermelons that are closer to 70 days and some varieties that will take closer to 100 days.
The biggest questions is, how do you know when a watermelon is ripe? This takes some practice, and there have been many times that I have brought a melon in only to find it not quite ready (and on the flip side, I’ve also brought in melons that are so spongy and overripe they are inedible).
How to Tell When a Melon is Ripe:
One way to judge ripeness is to thump the melon with your knuckles. If it produces a dull, hollow sound, your melon is likely to be ready.
You can also look at the tendrils on your watermelon vines. If the curly tendril immediately opposite the stem of the fruit is brown and dry, your melon is probably ready.
You can also look at the bottom of your melon, where it has been sitting on the soil. If this field spot is yellow instead of white, you melon is ready.
And finally, if you still aren’t sure if your melon is ready to pick, do some math. Each variety will have an average time to maturity. If you have been keeping good records in a journal or calender, you should be able to tell how many days old your watermelon plants are. If the age matches the days-to-maturity then you should be good to go.
Not keeping track? Pick up a copy of my Garden Planner and keep better records!
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© 2019, Sarah R Toney. All rights reserved.