Days to germination: 5 to 10 days
Days to harvest: 80 to 100 days
Light requirements: Full sun
Water requirements: Regularly
Soil: Loose and well-drained
Container: Not particularly
Traditional watermelons are quite large and may not be the best option for a small home garden. Black Beauty or Sugar Baby is a smaller variety with fruits more suited for family use. For something a little different, you can get yellow watermelon varieties too. Diana is yellow on the outside, and Golden Sunrise is yellow on the inside.
Watermelon is pretty much only eaten raw, and the rinds can even be pickled for another unique treat. The flesh of the watermelon is mostly water, which makes it the perfect summer fruit to eat. There is quite a bit of vitamins C, A, B6 and B1 in watermelon and very few calories.
If you don’t want to be spitting out the hard black seeds, plant seedless varieties instead.
Starting from Seed
Watermelons love the sun, so you will have to give your plants an early start indoors or they won’t germinate in the cool spring ground.
In peat pots, start watermelon seeds around 4 weeks before the expected last frost in your area. Don’t start your plants in plastic pots or seedling trays because the roots are delicate and can be damaged during transplant. You can just plant the entire peat pot instead.
Before you transplant your seedlings out into the garden, you need to decide how you plan on growing your watermelons.
Watermelons typically grow along the ground, taking up a lot of space in your garden (up to 10 feet of vines). If you are a bit more industrious, you can set up a trellis for your vines to grow upward instead. This is only a viable option if you are growing watermelons with small fruits (like the above mentioned Black Beauty). The vines won’t hold bigger fruit in place when on a trellis.
Even with small watermelons, you will likely have to help your plants with slings of fabric to hold them up while they grow. You can save space with a trellis, but it’s more work.
If this is your preferred approach, you can plant your seedlings in a row with about a foot of space between them.
For watermelons growing the old-fashioned way all over the ground, you can group 2 or 3 seedlings together in hills. Then keep your hills at least 4 feet apart for adequate room to grow.
Either way, dig up the soil so that it’s loose down at least 6 inches deep. Add compost or standard commercial fertilizer before you put in the plants. Cut open or tear out the bottoms of the peat pots for maximum rooting success, and plant out your seedlings without taking them out of the pots. They can go out in the garden 2 weeks after your frost date.
While your plants are first growing, water then every 2 or 3 days. Take care to water the soil and not the leaves or you can spread mildew infections among your plants. Once the fruit begins to grow, you can cut back the water just a little. The melons are mostly water after all. Some people limit the water quite a bit in order to make the fruit sweeter, but that works better with cantaloupe than watermelon.
For trellis growing, watch for developing fruit and get your fruit support hammocks in place before the melons actually need any support. It’s better that they grow into the nets rather than risk the fruit dropping off because you waited too long.
If you’ve let your watermelon grow along the ground, protect the melons from moisture and soil-borne pests with shield of some kind. Plastic lids or pieces of weather-proof tarp under them can keep your fruit out of the dirt.
As the weather starts to cool and your season is coming to an end, pinch out any flowers on your melon vines so that the plant can concentrate on the last few melons instead of growing new ones.
Watermelons are not the best plants for container gardening, though some plants are smaller than others. You may not save much space because the vines will still spread for many feet past the edge of the pot. Like in the garden, you can also try growing them upward but this can make the plant more top-heavy than most. Your container will need to be at least 5 gallons in size, or larger to really accommodate a watermelon plant.
The two varieties mentioned above (Black Beauty and Sugar Baby) are better for containers than larger fruited types.
Pests and Diseases
As part of the cucumber and squash family, watermelon are vulnerable to many of the same hazards in the garden as those other vegetables.
Cucumber beetles, squash vine borers and cutworms are all a problem for the watermelon patch. Check your plants every day and pick off the first two leaf-eating beetles. Spray with natural insecticide to help keep them at bay. The cutworms are caterpillars that live in the soil, and are harder to see. They can chew right through the stalk of a young plant, so if you see evidence of damage at the soil level, put cardboard or foil collars around the stalks to protect your plants.
If you see your plants developing a light coating of white dust, you likely have a problem with powdery mildew. This is one example of a fungus that can (and will) spread when you get the leaves wet every time you water the plants. Standard fungicide will help clear it up provided you catch it before it overwhelms the plant.
Harvest and Storage
Watermelons cannot be picked early, so you should not try to pick any small ones before their time. Depending on the variety, your watermelons will be between 2 and 12 pounds each. Most plants will produce between 3 to 6 fruits.
When the small tendrils near the stem of the watermelon yellow and dry up, the fruit is ready to be picked. A ripe watermelon will also have a hollow sound when you tap it with your knuckle but that can be hard to distinguish unless you’ve rapped a lot of watermelons. For the most part, your watermelons will all mature at roughly the same time.
Once picked, you can store a whole watermelon in the fridge for around 2 weeks. If you remove the pink flesh from the rind, you can freeze cut chunks of watermelon for later use.