"Squash" can refer to summer squash (Cucurbita pepo) and winter squash (Cucurbita maxima). These annual vining plants are grown in many home gardens and need plenty of room to sprawl across the ground. Winter squash generally requires more room than summer squash; there are more bush varieties available for warm weather squashes. You can pinch back both types of vines a few times during the growing season to control size and help produce fruit. Pruning summer squash, including zucchini, by harvesting immature fruits keeps it producing longer during the growing season.
Pinching back should begin when fuzzy tips begin to grow on the squash vines, usually in July. The pinching helps keep vines a certain size and allows them to focus on fruit production instead of growing new shoots. Continue to pinch back vines during fruit production so the plants focus their energy on the fruit growing on the vine. Pinching back makes plants produce less fruit, but what it does produce is larger and of better quality.
Trellis and Pinching
You can save room and improve air circulation in the garden by providing a trellis for the squash to climb. The vines can outgrow the trellis support just as they do their space when growing on the ground. You can pinch back the vines that extend beyond the trellis to encourage the plant to spread horizontally. Like pinching back vines on the ground, this pinching of vines on a trellis allows the plant to concentrate growth on developing fruit.
Toward the end of the growing season, pinch any blooms that develop on the vine to encourage the fruit on the vine to ripen and the plant to stop expending energy on producing new blooms. If these blooms are pollinated, the plant continues to produce new fruit that can be small and of poor quality.
Pruning and Fruit Production
Summer squash is picked before it matures, so harvesting the immature fruit is a type of pruning. Using a clean, sharp knife, cut the fruit of immature summer squash off the vine between the fruit and the main stem. Never pull fruits off the vine, because this can damage the plant. Once you stop harvesting the fruit, it matures and produces seeds, which signals to the plant that the growing season is over. If you have an abundance of summer squash, allow a couple of fruits to remain on the vine and mature to halt production.