Watermelon (Citrullus lanatus) is a vine-like, flowering plant in the Cucurbitaceae family originating from sub-Saharan Africa. Watermelon is grown in tropical and subtropical areas worldwide for its large, edible fruit. Watermelon cultivars differ in fruit shape, rind pattern, fruit size and flesh color. Varieties may be classified as open-pollinated, F1 hybrid, or triploid (seedless). Consumer demand for seedless watermelon has driven an increase in the production of those varieties. Seedless watermelons are developed with an odd number of chromosomes (33) and do not produce (or rarely produce) viable pollen and eggs in the resulting seedlings. Because of this, seeded watermelon varieties must be planted along with the seedless varieties for proper pollination.
Watermelon plants are self-fertile and bear separate male and female flowers on the same vine. Flowers are approximately 1-inch in diameter and range from pale to bright yellow. The pollination window is drawn out over a few months with plants producing a new flush of blooms after picking mature fruit. However, individual female flowers are only receptive to pollen for a single day. Flowers open early in the morning and close by the afternoon with peak-pollination occurring mid-morning. Proper pollination is important for achieving adequate fruit set, and bee pollinators are recommended at 1-2 hives per acre for pollen transfer from male to female flowers.