Watermelon Fertilizer Recommendations

Fertilizing at Planting Time

• When you first sow watermelon seeds or plant seedlings in your garden, you will need to fertilize the soil around the plant to provide it with enough nutrients to grow strong, healthy vines. A fertilizer high in phosphorus is ideal because this nutrient is responsible for the initial growth of most plants. Mass-produced fertilizers labeled 10-34-0 are often best because they also include a small amount of nitrogen, which will help the watermelon produce fruit.

Fertilizing During the Growing Season

• You will need to fertilize your watermelon once a month for two months after planting with additional nitrogen to keep the vines growing outward and encouraging them to produce fruit. You can use straight nitrogen for this, or simply an all-purpose garden fertilizer labeled 10-10-10. Apply the recommended amount one month after planting and then again the following month.

Commercial Fertilizers

• Store-bought fertilizer mixes, available at garden stores and many mass retailers, are one of the easiest ways to ensure your watermelon plants are getting all of the nutrients they need. These fertilizers' labels indicate the ratio of nutrients they have, with most containing nitrogen (N), phosphorus (P) and potassium (K). You can also purchase each nutrient individually. Some manufacturers sell products listed as organic and made from natural products. Guano, worm castings, fish fertilizers, kelp meal, blood meal, bone meal and gypsum can all provide the necessary nutrients for watermelon plants with fewer chemicals than standard garden fertilizers.

Homemade and Natural Fertilizers

• Many organic farmers and gardeners consider cow manure mixed with straw the ideal food for watermelons. If you are opposed to the use of animal manure, you can use a fish spray during the growing season to encourage healthy vines and fruit production. You can obtain phosphorus from rock phosphate, a natural fertilizer product sold in most garden stores. For an all-natural balanced fertilizer, try using a compost tea for your watermelon plants. This tea is made by steeping compost in water and then straining the mixture. Use the resulting liquid to fertilize the plants, which can also work as a natural insecticide.