Culture
This annual vine can easily be grown from seed. It is best grown in fertile, organically rich, consistently moist, well-drained loams in full sun. Thrives in long hot summers. Intolerant of wet soils. Avoid compacted soils. Vines spread out over the ground. Seeds may be planted outdoors when soil temperatures have risen to 70 degrees F., typically right after last spring frost date. Plant several seeds (up to six) together in hills that are 6-8' apart and thin later. Mulch around hills to help soils retain moisture and to discourage weed growth. Seed can also be started indoors about 3 weeks before the last spring frost date, with young plants set out after last frost date. Fertilize well. Fruits resting on mulch, straw or boards resist rot.
Noteworthy Characteristics
Citrullus lanatus is native to southwestern Africa. It is a scrambling, prostrate, hairy-stemmed, annual vine clad with curly tendrils and hairy, pinnately-lobed leaves. Stems grow to 10' or more. Pale green axillary flowers. Glabrous fruit is a spherical to oval watermelon that is typically green with darker mottling or striping. Over 1200 cultivars now exist, producing fruits from 6 to 50 pounds + (infrequently to 200 pounds or more). Each melon has a firm outer rind, a white inner rind and a sweet, juicy flesh (edible pulp) that is red, pink or yellow with imbedded black to brown seeds (seedless varieties are also available). Pick fruits only when ripe ("thunk" test with thumb). Notwithstanding the virtues of its fruits, this vine has become a common weed of roadsides and open ground some parts of the world.
Genus name comes from Citrus referring to the appearance of the fruit.
Specific epithet means woolly.
Problems
Anthracnose, blossom end rot, fusarium wilt, bacterial wilt, downy mildew and powdery mildew may appear. Watch for cucumber beetles which should be removed immediately by hand. Additional potential insect pests include aphids, squash bugs, stink bugs, cutworms, pickleworm and squash vine boreres. Watch for mites. Spray for insects at night when bees (needed for cross-pollination) are less active.
Uses
Cultivated watermelons are a popular summer fruit throughout the world. Edible melon-like flesh is juicy, sweet and tasty. Inner white rind is also edible. Rinds may be used as a vegetable. Watermelon rind can be pickled. Interesting wine.