Grow

Vines in the sand

UF/IFAS Gardening Solutions says Florida has a great climate for watermelon and is a leading producer for the nation, and adds the fact that surprises people: Florida is the only state in the country that produces watermelon from December to April. In a Central Florida yard the planting window opens in January.

Florida is the only state in the country that produces watermelon from December to April.

When to plant here

The window depends on where you are in the state. UF/IFAS puts North Florida at March and April. Central and South Florida can plant earlier, from January through March, because springtime temperatures get there sooner. South Florida gets a second shot in December. The reason behind the dates is a temperature range, not a calendar: watermelon grows best when daytime temperatures sit between 70°F and 85°F, and it will tolerate up to 90°F. The Florida Vegetable Gardening Guide carries the state planting tables if you want the vegetable-by-vegetable version, and the UF/IFAS What to Plant by Month list has watermelon under seeds for Central Florida in January.

Space is the real constraint

This is the part to settle before buying seed. UF/IFAS says growing watermelon takes in excess of 18 to 24 square feet per plant. A good rule of thumb where the seed packet does not say is 36 inches between plants, in rows 7 to 8 feet apart. If you plant a large variety you may end up with several 15 to 20 pound melons at once to eat, store, or give away. Fruit size runs 6 to 50 pounds depending on cultivar, and in rare cases as much as 200.

The answer for a small yard is an icebox variety. They are smaller, easier to harvest, easier to store, and they got the name because they fit in a refrigerator. UF/IFAS names Sugar Baby and Mickeylee for icebox size, and Jubilee, which it also calls Florida Giant, plus Crimson Sweet and Charleston Grey 133 for the large end. The heirloom Moon & Stars is a large variety with yellow dots on dark green rind, so it needs the space too.

Bed or container

Watermelon is the crop on this site that a container does not solve. The vine is an annual with curly tendrils and lobed leaves, and the 18 to 24 square foot figure is what it needs to make fruit. A pot can hold the roots of an icebox variety, but the vine still has to run somewhere, so the practical version is a pot at the edge of a bed with the vine trained across ground you were not using anyway. Full sun either way. UF/IFAS says watermelon is not fussy about soil type as long as it drains, which suits Florida sand.

How to start

1. Decide between seed and transplants. UF/IFAS warns that watermelon roots are sensitive, so if you buy transplants, look for ones grown in peat pots that go into the ground whole.
2. Pick full sun and any well-drained soil. Check your seed packet for spacing, since it varies by variety.
3. Space at 36 inches in rows 7 to 8 feet apart if the packet is silent.
4. Keep the plant unstressed. UF/IFAS ties the best-tasting melon directly to avoiding stress from insects, disease, weeds, poor nutrition, and too much or too little water.

Pests

The disease UF/IFAS leads with is gummy stem blight, also called black rot, a major fungal disease of watermelon and other cucurbits that can leave you with little or no edible fruit. There is no spray-first answer. The best way to avoid it is buying seed from a reputable company with a history of blight-free seed production. If you start with transplants, inspect for the symptoms: necrotic areas on leaf margins, water-soaked regions on the stem, and gummy ooze coming out of the stem. Keep debris from any other cucurbits you are growing away from the watermelons.

Rotation is part of the same defense. Plant where watermelons or other cucurbits have not been for the last two or three years. Handle fruit carefully at harvest, because a wound is an opening, and store melons at 45°F to 50°F to prevent postharvest black rot. Preventative fungicide is used in some areas. Powdery mildew and downy mildew also hit cucurbits here. For anything beyond identification, UF/IFAS sends you to your county Extension office, which is the right call for a spray decision.

When to pick

Watermelons take 80 to 100 days to mature depending on variety, and UF/IFAS admits outright that it can be difficult to know when one is ready. It gives two physical checks and neither is thumping. Look at the bottom of the melon where it sat on the ground: cream-colored or bright yellow means ripe, and a white or pale green spot means it is not. Then find the curled tendril closest to the melon on the vine. When that tendril turns brown and shrivels, the melon should be ready. Use both, because either alone can mislead you.

After that, the clock is short. A harvested watermelon lasts a little over a week at room temperature, or about two weeks refrigerated. A grid cutter turns a whole melon into cubes in one press, which is the difference between eating it and watching it sit. Get this. For scooping rather than cubing, a double baller does both sizes. Get this.

Questions

Sources

1. Watermelon, UF/IFAS Gardening Solutions
2. Florida Vegetable Gardening Guide (SP 103/VH021), UF/IFAS

The winter Florida melon versus the summer box, or the shop for cutters and ballers.