When to plant watermelon – to enjoy a delicious summer harvest

Best enjoyed on a warm summer's day, learn when to plant watermelon so you can be tucking into a fresh crop from your own kitchen garden. 

Full of vitamin C and potassium, watermelons are a delicious and nutritious fruit. It is easy to learn how to grow watermelon and once you know when to plant watermelon you can add them to the list of crops to nurture as part of your vegetable garden ideas. 

Watermelon can be grown really successfully a part of your vegetable garden container ideas, under cover if you're planning a greenhouse, and directly outside – all providing you get the timing right. 

Nothing says summer like that first taste of a fresh slice of watermelon. Blended into a smoothie or frozen as a popsicle, there are so many ways for the whole family to enjoy this deliciously sweet fruit.

If you are planning a kitchen garden, knowing when to plant watermelon is key to ensure a good crop. Here’s everything you need to know.

When to plant watermelon

Watermelon is a warm loving plant and will not tolerate any amount of frost, so knowing when to plant watermelon is really important to ensure a healthy crop.

The general rule of thumb is to plant watermelon in the spring about three weeks after your last frost date, or early summer. Your last frost date will vary depending on your USDA hardiness zone. 

As watermelon requires a long growing season, it could be a good idea to start your seeds as early as possible.

'Sow seeds under protection in pots from late February to early April,' suggests Steven Shirley from Victoriana Nursery Gardens. By sowing early, you will ensure a good harvest from late summer through to early fall. 

'Watermelon seeds will germinate at a temperature of around 75°F (23°C). The plants can be put outside in a heated greenhouse from March, or an unheated greenhouse from May,' Shirley advises. 

If, when deciding when to plant watermelon, you choose to sow directly outside, Kate Rowe, greenhouse coordinator at Seed Savers Exchange, suggests 'watermelons should be planted outside in late spring to early summer after the soil temperature has reached 70°F (21°C).' 

You should always check your last frost date for your specific hardiness zone before planting.

What is the best month to plant watermelon?

The best month to plant watermelon depends on a few variables. You must take into account your specific climate as well as the location you plan on planting the watermelons, for instance in a greenhouse or directly outside.  

Watermelons need warmth to germinate and, as such, a soil temperature of about 75°F (23°C) is perfect. They should be sown from early spring, about three weeks after your last frost date, and with some protection.  

'To get a head start on the season, especially in northern climates with shorter growing seasons, seed watermelons inside and transplant them, but be careful with their tender roots,' explains Kate Rowe. 

Mike Davidson from Platt Hill Nursery in Illinois, agrees. 'Watermelons can be started a couple of weeks before you put them out in your garden, a couple of weeks after your last frost free date. They should have germinated in a week or so.'

Once the watermelon plants are ready to plant outside, 'they need to be allowed to sprawl in the sunniest spot possible – ideally under protection in a greenhouse, polytunnel or similar – although a really warm and sunny sheltered spot outside should also be fine,' advises Shirley.

Because they do spread, watermelons can take up quite a bit of space in a small vegetable garden, but there is the option to plant them so they grow vertically as a vegetable garden trellis idea.

When can I plant watermelon outside?

Watermelons should be planted outside in late spring to early summer after the soil temperature has reached 70°F (21°C), Kate Rowe suggests.

It is a warm loving plant, and is simple to direct sow outdoors.  

As the plants are not frost hardy at all, 'look at the days to harvest and make sure to get them in, with plenty of time to harvest before a frost occurs,' Mike Davidson advises.

How long do watermelons take to grow?

Watermelons take about 70 to 100 days to grow, depending on the variety you have planted, and the conditions in which you are growing them.

As a warm loving crop, the plants need plenty of sun. 'Choose the sunniest spot to plant and grow your watermelon,' says Steven Shirley from Victoriana Nursery Gardens.

Now that you know when to plant watermelon, you’ll be able to grow your own delicious crop at home in your vegetable garden.