Note that squash is generally divided into two categories: summer squash (harvest in summer) and winter squash (harvested in autumn). The skin of summer squash is edible, unlike the skin of winter squash. Most summer squash now come in bush varieties, which take up less space, whereas winter squash are vining plants that need more space.
This guide focuses on summer squash. Summer squash varieties include zucchini, yellow squash (straightneck squash), and crookneck squash. Note: All types of summer squash require very similar care, so even though we mainly refer to zucchini on this page, consider it to be applicable to whatever summer squash variety you’re growing!
Zucchini is a vigorous grower. While each plant will produce several squash during peak season, you’ll typically find that one or two zucchini plants will produce a “bumper” (unusually large) crop, leaving you to give the squash away to neighbors or bake lots of zucchini bread!
Pick a location with full sun, shelter from wind for good pollination, and soil that is moist (not soggy) and well draining. Squash also produces well if well fed. Mix aged manure and/or compost into the soil before planting. Learn more about preparing soil for planting.
When to Plant Zucchini
- Direct-sow seeds (i.e., directly into the ground) when all danger of frost has passed and the air and soil are at least 60ºF. See your last frost date.
- If you wish to start seeds indoors, start seeds in peat pots 2 to 4 weeks before your last spring frost; note that squash seedlings do not always transplant well; handle the roots gently.
- Warm the soil with black plastic mulch once the soil has been prepared in early spring.
- Do not rush to plant zucchini. Consider planting a few seeds in midsummer to avoid problems from squash vine borers and other early-season pests and diseases.
How to Plant Zucchini
- Direct sow seeds in level ground 1 inch deep and 2 to 3 inches apart.
- Or, sow 3 or 4 seeds close together in small mounds (or hills; the soil is warmer off the ground) in rows 3 to 6 feet apart.
- If necessary, use row covers, or plastic milk jugs, or cold frame protection in cold climates for the first few weeks of spring.
- Thoroughly water after planting.
- Adding a layer on top of mulch (such as garden compost) to lock in soil moisture.
See our video showing how to sow and grow zucchini.
- Mulch to discourage weeds, retain moisture, and protect shallow roots.
- Zucchini thrive in moist soil. Water thoroughly, frequently, and consistently, with at least 1 inch per week. Water diligently when fruit form and throughout their growth cycle. The soil needs to be moist 4 inches down, so long soakings are best. Misshapen squash result from inadequate water or fertilization.
- Remove any weeds that manage to poke through. To keep plants tidy, cut off any dead or shriveling weeds. Top up mulches, using organic matter such as garden compost, to help roots stay cool and moist.
- When the first blooms appear, side dress with a balanced fertilizer.
- Poor pollination by bees can be an issue. Squash flowers will not bear fruit or bear small fruit if not pollinated. Most squash plants produce both male (these appear first, on long thin stalks) and female flowers (these have an immature fruit behind them). To fruit, pollen from the male flowers must be transferred to the female flowers by bees—or by the gardener. Pollinate the female flowers manually with a cotton swab or add plants that attract bees near the squash. See our article on how to hand pollinate your squash blossoms for better yields.
Zucchini produces well but you MUST keep an eye on the plant for pests. If you ignore zucchini, the pests will come, but you must get ahead of them before they arrive.
Two troublemakers often pay an unwelcome visit, usually early in the season.
- Squash bugs feed on sap, weakening plants and threatening fruit production. Protect plants when the bugs are most active, early on in the summer, by using row covers or fleece. Then continue to check for eggs at least twice a week. Rub or scrape off the eggs. Adult bugs can be knocked or shaken off plants into a bucket soapy water. (If you keep chickens, offer them a treat!)
- Squash vine borers are found in the eastern half of North America. They burrow into stems, causing them to rot and foliage to wilt. They are most active earlier in the summer. Row covers can help keep them off, or wrap stems in foil to prevent eggs from being laid at the base of plants. It’s possible to cut the grubs out by making vertical cuts into the stem using a sharp knife. Once you’re done, bury the stem with moist soil to encourage new roots.
- As far as diseases go, powdery mildew can be an issue on the leaves later in the season. It’s a common fungal disease that forms a white powdery coating on both sides of leaves. Usually growth stalls. A common reason for powdery mildew is irregular watering, so stay consistent. If plants do become infected, remove affected leaves straight away. A great way to prevent powdery mildew altogether is to mist leaves with a solution that is 1/3 milk to 2/3 water. Spray the milky mixture onto all surfaces, early on a dry and sunny day. Repeat every 10 to 14 days throughout the growing season.
- Blossom-end rot is an occasional issue as well. If the blossom ends of your squash turn black and rot, then your squash have blossom-end rot. This condition is caused by uneven soil moisture levels, often wide fluctuations between wet and dry soil. Uneven watering affects the calcium levels of the fruit. To correct the problem, water deeply and apply a thick mulch over the soil surface to keep evaporation at a minimum. Keep the soil evenly moist like a wrung out sponge, not wet and not completely dried out.
- ‘Cashflow’: cylindrical zucchini type
- ‘Cocozella (di Napoli)’: zucchini heirloom; dark green, slender
- ‘Goldbar’: yellow summer squash
- ‘Horn of Plenty’: yellow crookneck type
- ‘Sunburst’: pattypan/scallop type
- ‘Tigress’: zucchini type
Harvest summer squash when tender and a bit immature (6 to 8 inches long) for more flavor. Believe us, oversize squash has very little taste. Many people wait too long to harvest. If you have ever had a negative experience with zucchini before, it’s probably because they were left to become bruisers.
- Most varieties average 60 days to maturity, and are ready as soon as a week after flowering. (Check the seed packet for more exact information.)
- Cut (do not break) fruit off the vine with a sharp knife or you risk damaging the soft stem of the plant. Leave at least 1 inch of stem on the fruit.
- To slow production, harvest fruit when small and/or remove male flowers.
- If the harvest is interrupted (say, by your vacation), remove large squash on your return to reduce demands on the plants for moisture and nutrients.
- Complete the harvest before the first fall frost; summer squash is highly susceptible to frost and heat damage.
How to Store Zucchini
- Fresh summer squash has a relatively short shelf life. Store unwashed zucchini in a plastic or paper bag with one end open to encourage air circulation, and pop them in the refrigerator crisper drawer. They’ll keep for 10 days.
- Too much zucchini? Freeze it! It will keep for 3 months. See how to blanch and store zucchini in the freezer!
WIT AND WISDOM
- The word “squash” derives from askutasqush, the Narragansett Native American word meaning “eaten raw or uncooked.”
- So-called squash bees—Peponapis and Xenoglossa—are excellent pollinators especially for zucchini. Look for them among the flowers in the first few hours after sunrise.