Since zucchini is, in fact, a variety of squash, cross pollination of it with other squash is easily achieved and often desirable. Zucchini is also known as an Italian marrow, and comes in sub-varieties of its own, all due to cross pollination. These varieties include, but are not limited to, open pollinated species like Black Zucchini, Black Beauty, Cocozelle and Vegetable Marrow White Bush. Hybrid versions include Aristocrat, Chefini, Classic, Elite, Embassy, President, Spineless Beauty and Gold Rush. While zucchini can cross-breed with other summer squash, they are not able to do so with winter squash.
Cross-pollination strengthens a plant's yield, causing some of the best genes in each plant to be passed on to the fruit. This allows growth of species with heightened disease and pest resistance, making them more likely to survive through future generations. Insects like bees, butterflies, and even pests like the cucumber beetle are responsible for naturally occurring pollination. When the insect visits a male flower, it collects pollen on the hairs of its legs and body. It then visits a female flower and some of that male pollen is transferred to her, resulting in pollination.
In the event that your garden is lacking natural pollinators, which is likely if you use pesticides on your plants, you may have to artificially pollinate your plants. Another reason to use hand-pollination is if you are trying to cross-breed specific species of your squash --- trying for a certain color, size or taste in the resulting fruit. First you must identify male flowers from females: Males grow on a long slender stem and are more funnel-shaped than females. The female flower will additionally have a small growth beneath the flower, which is the fruit awaiting fertilization. Gently touch the center stamen (a slender protrusion in the center of the flower) of the male flower with your finger; if pollen comes off, the male is ripe. Pick the flower and carefully strip the petals back to fully expose the stamen. Brush the stamen all over the like part of the female flower.
There are times, like when you are trying to grow large squash such as for competition, that cross-pollination is undesirable. If you are attempting to grow an exceptionally large pumpkin, cross-pollination with a smaller squash will thwart your efforts. Aside from growing your pumpkins in a glass bubble, about all you can do to prevent this from happening is to avoid growing other varieties of squash anywhere near your pumpkins.
It is a myth that cucumbers and melons will cross-breed with squash. Although they do share the family name of cucurbits, they are too genetically dissimilar to cross-pollinate. Cucumbers and melons are vining plants, so while the flowers and leaves may bear a resemblance the squash plants, they are easy to identify on that count. This is good news for those who like some variety in their vegetable gardens.
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