When to Plant Winter Squash
In spring, sow seeds in prepared beds or hills after your last frost has passed, or sow them indoors under bright fluorescent lights. Set out seedlings when they are about three weeks old. In Zone 6 and warmer, you can plant more winter squash in early summer, using space vacated by fall-planted garlic or early spring lettuce. Stop planting winter squash 14 weeks before your expected first fall frost.
How to Plant Winter Squash
Winter squash grows best in warm conditions, in fertile, well-drained soil with a pH between 6.0 and 6.5. Choose a sunny site and prepare 3-foot-wide planting hills within wide rows, or position them along your garden’s edge. Leave 5 to 6 feet between hills. Loosen the soil in the planting sites to at least 12 inches deep. Thoroughly mix in a 2-inch layer of mature compost and a light application of balanced, organic fertilizer. Water well. Plant six seeds per hill, poking them into the soil 1 inch deep. After seeds germinate (about 10 days after sowing), thin seedlings to three per hill. Set up protective row covers as soon as you’re done planting. (See The No-Spray Way to Protect Plants for more information on how to guard your garden crops with row covers.)
Harvesting and Storage
Fruits are ripe if you cannot easily pierce the rind with your fingernail. Never rush to harvest winter squash, though, because immature fruits won’t store well. Unless pests or freezing weather threaten them, allow fruits to ripen until the vines begin to die back. Expect to harvest three to five squash per plant. Use pruning shears to cut fruits from the vine, leaving 1 inch of stem attached. Clean away dirt with a soft, damp cloth, and allow fruits to cure for two weeks in a spot that’s 70 to 80 degrees Fahrenheit. Store cured squash in a cool, dry place, such as your basement, a cool closet or even under your bed. Check every two weeks for signs of spoilage.
If you harvest your winter squash after the fruits have fully matured, saving seeds is simply a matter of rinsing, drying and storing the biggest, plumpest seeds that come across your cutting board. If stored in a cool, dry place, winter squash seeds remain viable for up to six years. Be sure to isolate varieties of the same species by planting them at opposite ends of the garden, or by growing one variety early in the season and another from midsummer to fall. Also keep in mind that acorn, delicata, dumpling and spaghetti squash can cross with summer squash, which is of the same species (Cucurbita pepo).
Preventing Winter Squash Pests and Diseases
Winter squash face challenges from squash bugs, squash vine borers, and cucumber beetles. To defend your plants from all three insects, shield them with row covers held aloft with stakes or hoops until the plants begin to bloom. Big, healthy plants will produce well despite pest pressure. Among diseases, powdery mildew is a common problem best prevented by growing resistant varieties, which often have “PMR” (for “powdery mildew resistance”) after their variety names. In addition, a spray made of 1 part milk and 6 parts water can suppress powdery mildew if applied every two weeks during the second half of summer. To see other readers’ squash bug prevention tips and post your own — and for instructions on how to make Mother’s own squash bug squisher — check out Homemade Squisher for Squash Bug Control.