Watermelon (Citrullus lanatus) is a traditional summer treat. Florida has a great climate for growing watermelon and is a leading producer for the nation. While it is generally considered a summer fruit, growers in Southern Florida are lucky enough to be able to plant watermelon for harvest in the winter as well.

Watermelon is in the cucurbit family along with other melons like cantaloupe and honeydew. Winter and summer squashes, gourds, pumpkins, and cucumbers are also members of the same family. Watermelon cultivation originated in Africa and has a long history around the world.

Watermelon is an annual vine with curly tendrils and lobed leaves; both the vine and its leaves are "hairy." It has pale yellow flowers, and the fruit is a round or oval shape with a firm, smooth rind that is typically green with darker marks or stripes. Depending on the cultivar, the fruit can range anywhere between 6 to 50 pounds, and in some rare instances, as much as 200 pounds. Each melon has sweet, juicy pulp that is red, pink, or even yellow. Seeds, if they exist, are black or brown; seedless varieties are also available.

Watermelon plants take up a considerable growing area — up to 18-24 square feet per plant. Luckily, there are smaller "icebox" varieties that are better for gardeners with limited space. Plus, the smaller fruits are easier to harvest and store (thus the name — they will fit in the refrigerator).

Watermelon can be planted either as seeds or transplants; care needs to be taken with transplants as the plants have sensitive roots. Transplants grown in peat pots that can be planted straight into the ground are best as this can help prevent stress to the young roots. Watermelons should be planted in full sun. The plants will grow in almost any type of soil as long as it is well-drained. The seed package should have the exact spacing needs. A good rule of thumb is that plants should be 36 inches apart and in rows 7 to 8 feet apart.

Watermelon plants grow best when temperatures during the day are between 70º and 85ºF, although they can handle daytime temperatures up to 90º. In North Central Florida watermelon can be planted in March and April and again in July and August.

There are a few varieties of watermelon that do particularly well in Florida. These include the popular smaller, icebox-sized watermelons “Sugar Baby' and 'Mickeylee'. Larger watermelons include 'Jubilee' (Florida Giant), 'Crimson Sweet', or 'Charleston Grey 133'. 

Watermelons are not without their vulnerabilities. (Pictured) Gummy stem blight (GSB), also called black rot, is a major disease of watermelon and many other cucurbits. GSB is a fungal pathogen that can lead to little or no edible fruits being produced. The best way avoid GSB is to purchase seeds from a reputable company with a good history of GSB-free seed production. Infected transplants may have characteristic GSB symptoms: necrotic areas on the leaf margins, water-soaked regions and/or gummy ooze coming from the stem.

Crop rotation is always a good idea when growing edible plants. Watermelons should be planted in an area where they or other cucurbits have not been planted within the last two or three years.

The use of fungicides may be necessary in some areas, and for some a preventative fungicide spray can be used to help avoid problems from GSB. In addition to GSB, powdery mildew and downy mildew can also cause problems for gardeners growing watermelons and other cucurbits.

To get the best-tasting watermelon, stress from insects, disease, weeds, poor nutrition, or too much or too little water should be minimized. Additional information on watermelon diseases may be found in reference 2 below.

Watermelons take 80 to 100 days to mature depending on the variety. It can be difficult to know when watermelon is ready to harvest. In general, the bottom of the melon should be cream-colored or bright yellow; a white or pale green spot means the melon is not yet ripe. The melon should be ripe when the curled tendril closest to the melon on the vine turns brown and shrivels, Once harvested, watermelons can last a little over a week when kept at room temperature or about two weeks when refrigerated.