Growing Watermelon in Your Square Foot Garden

Watermelons can be grown in a square foot gardening system. They are vine grown and can take up a lot of room in a normal garden. In a square foot garden you can only allow one square foot of ground, so all the growth has to be aerial. Ideally, you will plant two seeds in a square foot section and remove the weakest one if both germinate.

The Soil

The mix of soil in your square foot garden should be ideal for watermelon growth. If you can, it might be a good idea to have a slightly deeper garden box for the watermelons because they have deeper roots than many plants. One foot in depth should be sufficient.

Planting the Seeds

Watermelon seeds are triggered by frost to germinate. You should plant them towards the end of the winter so that they catch the last frost. It is possible to simulate this by putting the seeds in a freezer for half an hour. Typically, the seeds are planted in small hills 10 to 12 feet apart. In your square foot garden a hill is not necessary. It will help the watermelons if you work more compost into the square foot section before planting.

Training the Vines

Watermelons are well known for rotting on the vines if they grow along the soil. With your square foot garden you will have to provide a trellis to support your vines. You will be building vertical plants. The trellis can be a simple frame as high as you can make it. A simple trellis can be made with two 3 foot pieces of 2 inch diameter steel tube, two pieces of 2 inch by 2 inch timber 6 feet long and one piece of 2 inch by 2 inch timber the width of your garden box. Pound the steel tubes at least 18 inches into the ground at two corners of your garden box. Fasten a 6 foot length of 2 x 2 to each tube and fix the short piece of 2 x 2 across the top. Support for the plants can be provided by plastic coated netting fixed to the wooden frame that you have created.

Care of the Growing Fruit

Traditionally, watermelons are grown on the north side of a garden, but with vertical growth this is not a factor. The vine will be able to support the blossom and the early fruit which will naturally take up the ideal position for the light they need to receive. As the watermelons grow they will need additional support. This can be provided by using ‘hammocks’ made from any lightly woven material tied to the netting.

Watermelons always taste better if they ripen on the vine, so it is best to harvest them only when you need them. They will not rot on the vine while suspended in the air. Towards the end of the season there will be immature fruit and possibly blossoms on the vines. These should be taken off to encourage the vine to divert the remaining growth energy into the watermelons that are more advanced.
Watermelons are very successful in square foot gardens – you just need to ensure they are supported well so they don’t take over the whole area.