Unidentifiable plants may appear in your garden if you have recently taken over a previously owned plot, live in an area where seed spillage is likely, lost your plant labels or simply forgot what you planted. Because squash and melon plants are in the same family, Cucurbitaceae, they have many common features, making morphological traits poor means of identification. The best identifiers are the growing region, season of production and the properties of the plants and their fruit.
Compare your region and growing zone with the ideal growth conditions of squash and melons. For example, watermelon is a warm-season plant that grows best in southern states, making it unlikely that the plant would appear in a garden in Maine. Likewise, winter squash grows poorly in southern states.
Consult a growing calendar and use the seasonal harvesting information to guide your identification. For example, watermelons appear on the vine in June and grow through September, while summer squash will start appearing in May and winter squash may not be picked until August. A plant blossoming in April, therefore, is likely a summer squash or melon.
Examine the produce. Depress the skin with your thumbnail. If you are able to pierce the skin easily you most likely have a summer squash.
Note physical characteristics such as shape, size, color and skin toughness: pumpkins and buttercup squash have orange skin; watermelon has distinctive green skin with yellow-green stripes; bitter melon has a dry, wrinkled appearance; honeydew melons are round, light green and smooth; cucumbers have a cool, dark green exterior; acorn squash is acorn-shaped; and turban squash resemble two stacked discs.