When to Pick a Zucchini
Zucchini (Cucurbita pepo), also called summer squash, is a warm-season vegetable that should be planted after all danger of frost has passed. A frost-tender annual, zucchini can be once the soil has warmed to at least 60 degrees Fahrenheit. Most zucchini varieties reach maturity in roughly 60 days and are best harvested when still young and tender.
Plant the large zucchini seeds directly into the garden in the spring, or get a jump-start on the season by starting the seeds indoors several weeks before the last frost date for your area. Once the seeds have germinated, they develop quickly into vines that need plenty of space to sprawl. Flowers open in about 50 days, and the tiny squash appear soon after that. Growth proceeds rapidly from that point, and it's a good idea to start harvesting when the zucchini are no more than 6 to 8 inches long and up to 3 inches in diameter. At this stage, the squash is tender and sweet, and the seeds are small. It's okay to let them grow a little longer, but quality deteriorates rapidly in zucchini that are allowed to stay on the vine too long.
The large leaves on zucchini or summer squash plants are often prickly and conceal the bounty of fruit growing beneath them. When harvesting, select a dry sunny day, because working in the wet plants promotes disease. Gently move the leaves aside, being careful not to break them or damage any rootlets that have formed along the vines and taken hold in the soil. Using a sharp knife, cut through the thick stem about halfway from the blossom end, and harvest as many zucchini as you can to keep the plants producing.
Zucchini that are left on the vines too long past the ideal picking time often grow large, their skin toughens and the flesh becomes more fibrous. The seeds grow larger inside the fruit, too, and the once-tender and sweet flesh becomes waterlogged and loses much of its flavor and firm texture. While the squash are still edible at this stage, you generally have to peel them and remove the seeds and any tough fibers that have developed around the seeds. Zucchinis that were harvested young retain their shape during cooking, making them ideal for stir-fries and for stuffing and baking whole, while older fruit turns mushy more quickly because they take longer to cook.
Storage and Preservation
When storing your newly picked zucchini, opt for a paper bag over a plastic grocery bag, because the plastic encourages the production of moisture released by the squash. Stored in a paper bag in the crisper tray of your refrigerator, the zucchini will keep for up to 10 days. If you have a bounty of young tender zucchini, freeze what you can't use within 10 days by washing the squash, cutting it into rounds or cubes, and blanching it for about two minutes in boiling water. Remove the squash from the boiling water, plunge it into ice water, drain it on paper towels and freeze in plastic containers or plastic bags.