Watermelons (Citrullus lanatus) are a warm season crop that grows best at average air temperatures between 70 and 85 degrees F. The soil temperature at a 3-4 inch depth should be 60-65 degrees F before the crop is planted. Melon seeds do not germinate well in cold soils.

Watermelon seeds can be planted directly in the garden or transplants can be grown for an early start. Seeds or transplants should be planted in rows that are spaced 6-8 feet apart and plants should be spaced 5-6 feet apart in the row. A good rule of thumb is to allow 24 square feet per plant. If seeding the seeds should be planted about one inch deep. Transplants will generally be harvested two weeks earlier than direct seeded melons.

Recommended varieties include (Standard Varieties): Crimson Sweet, Royal Sweet, Sentinal, Sangria, Jubilee, Sugar Baby; (Seedless Varieties): Liberty, Majestic, Obsession, Fascination etc. You can also plant yellow and orange flesh watermelons now if you desire.

Growing watermelons (contributed photo.)

It is best to base your fertility program on a soil sample. If no soil sample is available, apply 10 lbs of 10-10-10 fertilizer per 1,000 square feet before planting. Melons should be side-dressed before the vines start to run. Sidedress with 34-0-0 at two pounds per 100 feet of row. Sidedress a second time if needed when fruit is developing on the vine.

Watermelons require a lot of water. The watermelon is comprised of up to 92% water. As with most plants the watermelon vine roots are concentrated in the top 12 inches of soil. Therefore, water to a 12- inch depth is crucial to the success of watermelon production. It is critical to maintain irrigation cycles during fruit set and development. If watering overhead it is best to water in the morning to prevent foliar diseases.

Watermelon plants have male and female flowers. For proper fruit development, sufficient pollen must be moved from the male flower to the female flower. Pollen can be moved with wind, but for best pollination results insects such as honeybees, native bumblebees and other pollinators are necessary for proper pollination. Seedless varieties do not have viable pollen and will need a seeded variety planted within 10 feet to provide adequate pollen for seedless watermelon fruit set. Often, when buying seedless packs of watermelon seeds the package will mention that there is a pollinating variety mixed in the packet.

Seedless watermelons are created by crossing two genetically different watermelons to produce a sterile hybrid plant. The resulting hybrid plant (triploid plant) has an odd number of chromosomes, making it sterile and unable to produce mature seeds. Therefore, the seeds are inconspicuous and white in nature. The seedless watermelon seed results when the tetraploid hybrid plant is pollinated by a normal plant (diploid plant) and the resulting seed then produces the triploid plant that produces the seedless watermelon.

When ready to harvest there are signs that you should look for to determine if the melon is ripe or not. The signs include: does the fruit look to be the expected size, the tendril closest to the fruit turns brown, the skin color loses its gloss and becomes dull in color and the bottom of the fruit has a large white to cream color oval spot. Generally it takes 35-40 days from fruit set to ripening. Most varieties take between 85-90 days from seeding to the first ripe fruit.

Problems that you might encounter when growing watermelons may be mis-shapened fruit from poor pollination, blossom end rot caused by calcium deficiency and insect problems from cucumber beetles or squash bugs. The most efficient and cost effective disease control measure is rotating the crop and avoiding planting in the same areas as cantaloupes, cucumber, squash and pumpkins for at least three years.

For more information about watermelons, or if you have other gardening questions, feel free to contact the N.C. Cooperative Extension, Franklin County Center at 919-496-3344. Stay tuned for nutritional information about watermelons in the next Growing in Franklin article.