Winter squashes are members of the Cucurbitaceae family and relatives of both the melon and the cucumber.
Winter squashes like butternut or pumpkin have hard shells that are difficult to pierce, enabling them to have long storage periods under the right conditions, making them an essential crop for anyone trying to grow a lot of their own food.
History of Winter Squash
Modern day squash developed from wild squash that originated in an area between Guatemala and Mexico. While squash has been grown and eaten for over 10,000 years, they were first cultivated specifically for their nutritious seeds because early squash did not contain much flesh, and what they did contain was very bitter.
As time progressed, squash cultivation spread throughout the Americas, and varieties with a greater quantity of sweeter-tasting flesh were developed. Christopher Columbus brought squash back to Europe, and like many other native American foods, their cultivation was introduced throughout the world by Portuguese and Spanish conquerers.
Today, there are hundreds of beautiful varieties of winter squash, and the largest commercial producers include China, Japan, Romania, Turkey, Italy, Egypt, and Argentina.
Culture and Cultivation of Winter Squash
Winter squash need warm soil (60 degrees F) to germinate so either start your seeds indoors or direct seed outside once the weather warms up.
If starting indoors, plant your seeds in 3-inch seed pots rather than flats, placing the seeds about an inch under the soil. You can plant 2 or 3 in each pot, to transplant together in hills.
Keep your pots somewhere sunny and warm or they may take a long time to sprout. Get them started about 3 weeks before your last frost date.
Each winter squash plant will produce several large squash, so you won’t need more than 3 or 4 plants unless you have a big family. Transplant your seedlings about 2 weeks after your last frost has passed.
If you are putting seeds straight into the garden, plant them at the same time as you would put out your transplants. They will not germinate or sprout in cold soils. Plant 4 or 5 seeds in a small hill, and thin down to 2 or 3 after they have sprouted.
Winter squash like a fertile, well-drained soil with plenty of compost. Plant them in a location that will have full sun and allow a lot of space for the vines. Each hill should have 3 feet of space around it. Mulch them well with straw to keep the soil from drying out too fast.
Winter squash can be grown upward on a fence or trellis if you don’t want to have vines all through your garden. If you plan on training them up this way, you can plant your seedlings just 2 feet apart. In this case, don’t plant them in little groups, but rather just one plant every 2 feet.
On trellises, the plant won’t be able to support heavy, mature squashes up in the air on its own. So get creative and support those fruits with slings or nets fashioned from pantyhose, old t-shirts, or mesh produce bags. Just be sure to tie them to the trellis, not the vines.
Like cucumbers, squash vines will first have a round of male-only flowers come to bloom before the female ones do. So don’t be alarmed if none of the first blossoms set any fruit. They aren’t supposed to.
As the season comes to a close, you can help the plant divert its resources to finishing off the larger squash before winter by pinching off any new flowers and removing very young squash.
Troubleshooting Squash Pests and Diseases
Plants are eaten or cut off near soil level. Cutworms are gray grubs ½- to ¾-inch long that can be found curled under the soil. They chew stems, roots, and leaves. Place a 3-inch paper collar around the stem of the plant. Keep the garden free of weeds; sprinkle wood ash around base of plants.
Leaves curl under and become deformed and yellowish. Aphids are tiny, oval, and yellowish to greenish pear-shaped insects that colonize on the undersides of leaves. They leave behind sticky excrement called honeydew which can turn into a black sooty mold. Use insecticidal soap.
Leaves turn pale green, yellow, or brown; dusty silver webs on undersides of leaves and between vines. Spider mites suck plant juices causing stippling. Spray with water or use insecticidal soap or rotenone. Ladybugs and lacewings eat mites.
Leaves yellow; tiny white winged insects around plants. Whiteflies will congregate on the undersides of leaves and fly up when disturbed. Remove infested leaves and the whole plant if infestation is serious. Introduce beneficial insects into the garden.
Holes chewed in leaves, leaves skeletonized; runners and young fruit scarred. Spotted cucumber beetle is greenish, yellowish, ¼ inch (7mm) long with black spots and black head. Striped cucumber beetle has wide black stripes on wing covers. Hand pick; mulch around plants; plant resistant varieties; dust with wood ashes. Cultivate before planting to disrupt insect life cycle.
Holes in leaves and flowers; tunnels in vines and fruits. Pickle worms are the larvae of night-flying moths. Moths lay eggs on squash plants. Caterpillars feed on leaves and inside vines and fruits. Pupae may be found inside rolled leaves. Exclude moths with floating row covers. Plant fast-maturing varieties to promote strong growth before pickleworms attack. Plant a few squash as trap crops. Keep garden clean.
Leaves have yellow specks that turn brown, then black and crisp; vines wilt from point of attack. Squash bug is a flat, shield-shaped black or brownish bug with a triangle on its back; it sucks juices from plants. Trap adults beneath boards in spring, hand pick and destroy. Look under leaves for bugs.
Runners wilt suddenly; holes in stems near base of plant. Squash vine borer is a fat, white caterpillar with a brown head that emerges in late spring. It bores into stems to feed causing plants to wilt. Look for entrance holes where frass may accumulate; slit vine with knife and remove borer; bury runner at that point to re-root. Exclude adult moth with floating row covers. Time planting to avoid insect growth cycle. Plant resistant varieties.
Round to angular spots on leaves, reddish brown to black. Anthracnose is a fungus disease that spreads in high humidity and rainfall. Leaves may wither and fall. Plant may die back. Generally found in eastern North America. Spray or dust with a fixed copper- or sulfur-based fungicide every 7 to 10 days. Remove and discard infected plants. Avoid working in the garden when it is wet which can result in spread of spores. Keep tools clean.
Water-soaked blotches on leaves or fruits. Angular leaf spot or bacterial spot is a waterborne bacterium which causes irregular geometric patterns on leaves. Spots may turn yellow and crisp. Avoid wetting foliage with irrigation. Prune off infected leaves and stems. Clean up garden. Plant disease-resistant varieties. Rotate crops up to 2 years.
Round white powdery spots and coating on leaves. Powdery mildew is caused by fungal spores. Spores germinate on dry leaf surfaces when the humidity is high; spores do not germinate on wet leaves. Common in late summer or fall but does not result in loss of plant. Avoid water stress. Pick off infected leaves and use this disease preventing spray.
Irregular yellowish to brownish spots on upper leaf surfaces; grayish powder or mold on undersides. Downy mildew is caused by a fungus. Improve air circulation or use trellises. Plant resistant varieties. Rotate crops. Keep garden free of plant debris and use this disease preventing spray.
Mottled, distorted leaves. Mosaic virus causes leaves to become thickened, brittle, easily broken from plant; plants are stunted and yields are poor. The virus is spread from plant to plant by aphids and cucumber beetles. Remove diseased plants.
Vines wilt suddenly and die starting with one or two leaves. Bacterial wilt clogs the circulatory system of plants. It is caused by bacteria that live in cucumber beetles and is seen often where the soil stays moist. Remove and destroy infected plants before the disease spreads. Control cucumber beetles with rotenone or sabadilla. Wash hands and clean tools with a bleach solution and use this disease preventing spray.
Plants are stunted and yellow; runners gradually die. Fusarium wilt is a fungal disease which infects plant vascular tissues. Fungal spores live in the soil and can be carried by cucumber beetles. Plant disease-resistant varieties. Rotate crops. Remove and destroy infected plants. Fungicides are not effective.
Water-soaked or pale green spot on leaves that turn white; fruit cracks. Scab is caused by soilborne bacterium. Disease can be cosmetic. Plant resistant varieties. If scab occurs, change varieties next year. Sulfur may be worked into soil to make it slightly acidic and reduce disease.
Stems on older plants appear water soaked and turn into cracked brown cankers; fruits become water soaked. Gummy stem blight and black rot are fungus diseases. Infections can girdle stems can cause collapse. Remove and destroy infected vines. Rotate crops where fungus can persist. Grow powdery mildew resistant plants.
Some seeds fail to germinate and come up. Some squash seed are “hard” and resistant to water uptake necessary for sprouting. Soak seed in tepid water for 24 hours before planting; this will increase germination and decrease sprouting time slightly. Dry seed before planting.
Early flowers don’t set fruit. A couple of possible reasons: (1) the first flowers to appear are male; female flower appear next. Fruit is produced by female flowers. Wait until female flowers appear and are pollinated. (2) There may not be enough pollinators, mostly bees, to carry the pollen from male to female flowers. Pick off male flowers and dust the pollen into the female flowers.
Few fruits form even though plants are flowering. Not enough bees. The more bees the more flowers that are likely to set fruit. The average size of a squash is increased when the vine is pollinated by many bees.
Small fruits form then dry up. Female flowers may have blossomed before the male flowers so the female flowers went unpollinated. When female and male flowers blossom at the same time pollination will occur and fruit will grow.
Fruits turn brown or rotten on one end. Blossom end rot means there the plants aren’t getting enough calcium, water or both. Learn more here.
Dense white mold on blossoms or small fruits. Choanephora fruit rot is a fungus that grows on blossoms and developing fruit. Remove and destroy infected blossoms and fruits. Keep the garden clean of debris that can harbor fungus. Rotate crops.
How to Store Winter Squash
Depending upon the variety, winter squashes like butternut can be kept for one month to six months. The thicker the rind, the longer they tend to keep.
Keep winter squash away from direct exposure to light and do not subject them to extreme heat or extreme cold. The ideal temperature for storing winter squash is between 50-60°F (about 10-15°C).
Once it is cut, cover the pieces of winter squash in a glass storage container and store them in the refrigerator, where they will keep for a few days. The best way to freeze winter squash is to first cut it into pieces of suitable size for your individual recipes.
All winter squashes need to be peeled and de-seeded before cooking. Save the seeds though; all winter squash seeds (not just pumpkin) are outstandingly nutritious, and can be dried, roasted and salted or seasoned with cayenne, cumin, ginger or other spices for a delicious snack!