Edibles

Squash (Winter): Sow and Grow Guide

Squash (Winter): Sow and Grow Guide

The varied colors of winter squash makes us yearn for fall and cool temperatures. Richly flavored winter squash can create endless sweet or savory culinary creations. Winter squash, including pumpkins, usually grow on vines (some compact bush types are available), and are harvested when seeds are mature, and the outer skin is hard; they can be stored for 2 to 6 months, depending on type.

Did you Know? Summer and winter squashes are closely related, and in some cases summer squash can be left to mature into winter squash. They have similar growing instructions and are afflicted by the same pests, too. They are, of course, different in growth and fruit. The word squash comes from the Narragansett Native American word, askútasquash, which means “eaten raw”, even though these days we most often cook squash.

GENERAL SOWING

When to sow outside: RECOMMENDED. 2 to 4 weeks after your average last frost date, and when soil temperatures have risen to 70°–85°F.

When to start inside: Not recommended except in very short growing seasons, 2 to 4* weeks before transplanting. Use biodegradable pots that can be planted directly in the ground, minimizing root disturbance. *Be cautious to not mature seedling over 4 weeks as plants become stressed and potentially stunted.

How many do I plant?
Since winter squash can be stored for several months, gardeners have more time to process and preserve the harvest by freezing or canning, making the bounty of winter squash less overwhelming. Usually, space is a bigger factor for winter squash than the amount of harvest, since winter squash can take up a fair amount of room in the garden. We offer some compact type winter squash too, so even container gardeners can enjoy the sweet storage fruit.

INDOOR SOWING

If you have a shorter growing season, you may consider starting your squash seeds indoors. Use a lightweight seed starting mix/media (sterile, and lighter than potting mix), and sow summer squash seeds 1/2”–1" deep, and winter squash 1” deep. Sow 2–3 seeds per pot, thinning to the strongest plant once leaves appear (clip extra plants at the soil level using scissors). The strongest plant may not be the tallest; look for thick, strong stems and deep color. By thinning early, you minimize the negative impact of crowding, like stretching for light. Read about more indoor sowing tips.

Containers
Sow in 3”–4” biodegradable pots that can be planted directly into the ground, minimizing root disturbance. Biodegradable paperboard pots are the ideal size, easy to label, and convenient for sharing plants with friends. Squash roots are sensitive to transplanting, which is why direct sowing is our recommendation.

Transplanting
Harden off seedlings after 2 ½ to 3 weeks. Hardening off is the 7 to 10 day process of introducing pampered seedlings to the intense outdoor sun and temperature swings. Read more about hardening off instructions.

Transplant into an area of full sun (6 or more hours a day), when soil temperature is at least 60°F. If you don’t have a soil thermometer, this is often about 2 weeks after your last frost, but double-check the weather forecast. Transplant on a cloudy day or in the evening to reduce stress. Remove the bottom of the biodegradable pot when transplanting into the planting hole. This allows roots to escape easily while the remainder of the pot breaks down.

OUTDOOR SOWING

Sowing or transplanting preparation and spacing
Amend the soil ahead of time. We suggest submitting a soil test periodically, which gives you detailed information on your soil and how to improve it. Over-fertilization can invite pests, reduce fruit yield in favor of leaf growth, impact flavor, burn plants, or be a pollutant. Work soil so it is clump free, allowing it to drain well, and apply any additional fertilizer and/or organic matter needed. Initially, you just want the plants to grow, so usually a balanced fertilizer is best.

Winter squash is commonly grown in mounds 4’–8’ apart. Raised mounds warm the soil more quickly in spring, and drain well. Vining winter squash can be grown on a trellis to save space, and increase airflow, which helps prevent fungal disease. If you choose to grow on a trellis, plants may be spaced more closely (half spacing). Larger fruits (over 4 lbs.) should be supported with a makeshift sling made of material like old t-shirts, pantyhose, or other soft materials. Some winter squash can mature to 25 lbs, which may be difficult to manage on a trellis and will require a very strong structure. Keep in mind the vine length and mature fruit size if you choose to use a trellis. Grab some ideas on trellising from our tomato trellis blog.

Weeding
Keep areas weed-free, but cultivate shallowly as to not disturb shallow squash roots.

Fertilization
Once your plants are almost ready to produce flowers and fruit, you can apply a phosphorous-rich liquid fertilizer to encourage blooming. Apply 4 weeks from transplant, or 6 weeks from seedling emergence if direct sown, repeating monthly. However, we always recommend a soil test to check for phosphorous levels first.

Water
It is normal for squash leaves to wilt in the heat of the day and recover overnight; it’s their way of conserving water. To know if your plants need water, poke a finger into the mound, if you feel moist soil 2” down you can wait to water, but at about 3” go ahead and water. Avoid watering the leaves of the plant as it can encourage powdery mildew, a fungal disease that attack the plant leaves.

POLLINATION

Both summer and winter squash have separate male and female flowers on the same plant (“monoecious”). Bees are needed to transfer pollen from the male flower to the female flower, which produces the fruit. Male flowers appear earlier in the season than female flowers, in theory to attract bees to the area, so don’t be alarmed if the first flowers do not produce fruit. Squash, as a native, has co-evolved with native “squash” bees. Squash bees are ground nesting and you can create habitat for them by leaving a weed-free dirt patch open and unmulched. Native squash bees are active earlier in the morning than the European honeybees and are also superior pollinators. Squash bees are focused on collecting pollen from all the flowers on the squash plants vs. the honeybee, which will collect pollen from many plants and may go to a few squash flowers and be distracted by another flowering species. Because squash bees are focused on squash, they ensure more female flowers are pollinated completely, resulting in more and better-shaped fruit.

If you’re not seeing any bees, sow bee-attracting flowers that bloom in early summer, like borage or alyssum, near squash plants. If bees continue to be few and far between, hand pollinating may be necessary. Use a paintbrush, or remove one male flower and press it into female flowers (one male flower can be used on up to 10 female flowers). (More about hand pollination)

Since squash are so dependent on bees, take extra precaution in applying any pesticides (organic or otherwise). Do not apply pesticides to flowers, and apply very early in the morning or late in the evening when bees are less active; if you have native squash bees, evening may be best.

HARVESTING

Blossoms
Look for male, non-fruit producing flowers (female flowers have a swollen mini-squash at the base of the flower and flowers are on shorter stems) and harvest just before use.

Harvest just before the first fall frost when the squash’s rind is hard enough that you can’t dent it with your fingernail. Cut stem (don’t break it off), leaving 2" of stem attached, which keeps the squash whole, leaving no opening for infection. Though fruits are hard and may seem indestructible, treat them gently; bruising can spoil squash. Read more information on harvesting and storing winter squash.

Winter Squash Comparison

Variety Heirloom Plant
Size
Fruit
Size
Disease / Pest Resistance Storage
Length
Days to
Maturity
Noteworthy Other Common Names
Squash Winter Blue Hubbard HEIRLOOM Seeds ‘Blue Hubbard’ X 10'–20' 10–30 lbs, teardrop shape   5 months 100–110    
Squash Winter Delicata Honeyboat Organic Seeds ‘Honey Boat Delicata’   6' 6"–8" long   2–3 months 90    
Squash Winter Gold Nugget Organic HEIRLOOM Seeds Gold Nugget X 3' 3"–4" globe   6 months 90–100 Bush type.
AAS winner, Container friendly.
Oriental Pumpkin
Squash Winter Lakota Organic HEIRLOOM Seeds Lakota X 10'–20' 4-8 lbs, 8-10" long   6 months 85–100    
Squash Winter Pink Banana HEIRLOOM Seeds Pink Banana X 12'–15' 10-12 lbs, 18"–24" long   6 months 100    
Squash Winter Red Kuri Organic HEIRLOOM Seeds Red Kuri X 4'–6' 3–4lbs teardrop shape   2–3 months 95   Baby Red Hubbard, Orange Hokkaido, Uchiki Kuri
Squash Winter Sweet Meat HEIRLOOM Seeds Sweet Meat X 10' 10–15 lbs   6 months 95–110    
Squash Winter Sweet REBA Acorn Organic Seeds Sweet REBA Acorn

 

4' 1½–2 lbs Powdery mildew resistant 2–3 months 90–100 Bush type. Container friendly.  
Squash Winter Table King Acorn Seeds Table King Acorn   4' 2 lbs   2–3 months 80 Bush type. AAS winner, small spaces, container friendly.  
Squash Winter Vegetable Spaghetti HEIRLOOM Seeds Vegetable Spaghetti X 8'–12' 8"–12" long   2–3 months 90   Gold string melon
Squash Winter Waltham Butternut Seeds Waltham Butternut   8' 3–6 lbs, 8"–12" long Solid stems resist borers   100 AAS winner  


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