These sun lovers are sensitive to cold, though winter squash tolerate light shade and cooler nighttime temperatures better than summer squash.
Both types of squash are heavy feeders and need a light and well-drained but moisture-retentive soil. You can give them exactly what they need by planting them in specially prepared hills. See the Melon entry for details on creating super-charged planting hills. Space the hills 3 feet apart for summer squash; vining winter squash need 6 to 8 feet between hills.
Summer squash can cross-pollinate with various cultivars of both summer and winter squash, as well as with several types of pumpkins. This won't affect the current season's fruit, but if you want to save seed, be careful not to let crops cross-pollinate. Otherwise, the seed won't be true to type, and the following season's crop will potentially be strange-looking or-tasting hybrids.
A week after the last frost date, or when the soil temperature is at least 60°F and the weather has settled, sow six seeds 1/2 inch deep in a circle on the top of each hill. Thin to the two strongest seedlings per hill.
If planting in rows instead of hills, space vining cultivars 3 to 4 feet apart in rows 8 to 12 feet apart; space bush types 2 to 3 feet apart in rows 4 to 6 feet apart. To conserve space in small gardens, train squash vines on a tripod. Tie three long poles together at one end, stand them upright, and spread them out to form the tripod; plant a squash seed at the base of each pole. You can also grow vining types on fences and well-supported growing nets.
In areas with short growing seasons, sow the seeds indoors a month before the last frost date. Plant two seeds per 3-or 4-inch pot, using potting soil enriched with extra compost. Clip off the weaker seedling after seedlings emerge. Water well just before transplanting, and disturb the roots as little as possible. Full-grown plants can tolerate cold weather, but seedlings are very cold sensitive. Use hotcaps or cloches to protect them until the weather turns hot.
Summer squash will produce more heavily than winter squash. In either case, unless you plan to preserve or store a great deal of your crop, two vines of either summer or winter squash are probably adequate to feed four people. Unused seeds are viable for 4 to 5 years as long as you store them properly. To spread out the harvest, start a second crop about 6 weeks after the first planting; it will begin to produce fruit about the time your first planting has peaked and the plants are declining.
Give seedlings lots of water and keep the planting area moist throughout the growing season. To avoid such diseases as mildew, water the soil, not the foliage, and don't handle plants when they are wet. Dig weeds by hand until the squash vines begin to lengthen, then spread a thin layer of compost and top it with a thick mulch of hay, straw, or chopped leaves.
About 6 weeks after germination, male blossoms will appear, followed by the first of the female flowers. Squash depend on bees and other insects for pollination; female blooms that drop off without producing fruit probably weren't fertilized. You can transfer pollen from the male stamen to the female pistil by hand, using a soft paintbrush. Or simply pluck a male flower, remove the petals, and whirl it around inside a female flower.
If your garden soil is less than ideal, side-dress plants with compost or a balanced organic fertilizer or drench them with compost tea when the first fruits set. Lear how to make compost tea.
When vines grow to about 5 feet, pinch off the growing tips to encourage fruit-bearing side shoots. By midsummer, winter squash will have set all the fruit they will have time to mature; remove all remaining flowers so the plant can put its energy into ripening the crop. To avoid rot, keep maturing fruit off the soil by setting them on a board or flat rock or by spreading a thick mulch. This is particularly important with winter squash, which take a long time to ripen.