Growing Squash: How to Plant, Grow, Harvest, and Store

Crookneck, tromboncino, kabocha…no, those aren’t the names of characters from a fantasy novel. But they are a few of the many varieties of squash available for growing in your garden. From tender, quick-growing zucchini to sweet and dense butternut, squash is a rewarding and easy-to-grow vegetable that adds richness to meals and replaces high-carb, low-nutrient foods.

In this guide, we’ll walk you through everything you need to know about growing squash at home—including planting, growing, harvesting, storing, and using.

Getting started growing squash

Summer vs. winter squash: what’s the difference?

In its simplest form, squash is usually divided into two categories:

Summer squash grow quickly (in about 60 days) and are harvested throughout the summer while still young. Their skins are thin and tender and they tend to be prolific producers. Zucchini is the most common summer squash. Pattypan are another equally tasty variety.

Winter squash grow more slowly (80 to 110 days) and often mature to a rich color before harvest. Their skins are thicker and more protective, making them last longer in storage. Well-known winter squashes include pumpkin, Hubbard, and butternut.

Which type of squash to grow?

Choosing the best squash varieties is a matter of personal taste, but often what you grow comes down to what you want to use it for. Would you like to eat your squash right away? If so, don’t grow one of the many varieties that need time to sweeten up. Do you want to grow your own Halloween pumpkin? Be sure not to choose a giant!

Here are some of the most commonly grown squash varieties.

Planting and growing

Once you’ve decided what type of squash to grow, consider the following questions.

When is the best time to plant squash?

Both summer and winter squash are warm weather plants. Wait until the soil temperature has warmed to at least 60 F (16 C) before direct seeding to ensure your seeds don’t rot before they sprout. You can also sow your squash seeds inside or in a heated greenhouse 2 to 4 weeks before the last frost date. The same goes for transplants: don’t set out until the weather has warmed to 70 F (21 C). Check with your local extension agent for up to date information in your neighborhood.

How much space do I need for squash?

In general, squash plants like lots of room to spread out. But just how much depends on whether you’re growing bush or vining varieties. Consider the following recommendations:

Bush varieties: Space your rows 4 to 6 feet apart, with plants 15 to 20 inches apart.

Vining types: Space rows 6 to 12 feet apart with plants 12 to 15 inches apart. If you plant in hills—a favorite of many gardeners—space your hills 6 to 8 feet apart. You can space vining squash more closely together, but you’ll have trouble finding them amongst all the leaves.

Should I grow squash from seeds or starts?

That all depends: do you have enough time to grow mature squash from seed (check your packages for the number of ‘days to maturity’)? If you do, starting from seed is the most economical way to grow. It’s also the easiest, since squash generally don’t like being transplanted.

Seeding squash directly into the ground starts with choosing your favourite seed, soaking the seed overnight (optional), and planting 3-6 seeds in a cluster. Once the seeds have sprouted, choose the strongest and remove the rest. When your plants have their first set of true leaves, mulch the soil to retain moisture. Keep the mulch back from plants a few inches to discourage stem rot.

Related: Tips for Growing the Best Winter Storage Vegetable: Winter Squash

If you don’t have enough time to start squash from seed, buying a few starter plants from your local nursery or farmer’s market is a good way to get a jump on the season. This works particularly well in colder climates where the growing season is short. Most plants will recover from the shock of being moved. Just remember to minimize disturbance to the plants’ roots.

How much sun do squash plants need?

Squash plants need full sun to produce. Make sure you’re planting your seeds or starts in an area with at least 6 hours of sunlight per day. (You can use a sunlight calculator to find out.) More is better, but if the weather gets too hot for too long, your squash plants may droop with stress. If this happens, it’s a sign your plant is trying to conserve its resources. Most will perk up again when the heat subsides in the evening, but if they don’t, consider adding a shade cloth or other temporary heat protection.

What about soil requirements?

Squash like a slightly acidic soil: between 6.0 to 6.8 pH is best. If your soil is too acidic, add lime according to the instructions on your product. But don’t worry needlessly. According to the University of Massachusetts Centre for Agriculture, squash can tolerate a soil pH as low as 5.5, so don’t worry about liming unless your soil is strongly acidic. Always perform a soil test before adding anything that will affect your soil’s pH.

Related: How to Build and Nourish Healthy Garden Soil

Squash are heavy feeders and benefit from soil rich in organic matter. Plant where you’ve added seasoned manure or finished compost. For best results, work in 1 cup of complete organic fertilizer beneath your transplants. If planting from seed, work the fertilizer into the top 2 to 3 inches of soil.

How often should I water squash plants?

Squash need one inch of water per week. To put that into perspective, you’ll need to water mature squash plants once a week so the soil is moist 8 to 12 inches beneath the surface. If your soil is very sandy or the weather is smoking hot, you’ll need to water more frequently.

Drip spikes attached to a drip irrigation system are an excellent way to ensure your squash plants get adequate water. Another method involves burying a perforated tin can beside your seedling at planting time, and filling this can daily to a few times per week. Using this method, you’re sure to get water to your plants’ roots.

Common pests and diseases

Like any garden crop, winter and summer squash are susceptible to some pests and diseases.

Squash vine borers

Squash vine borers tunnel through the stems of squash plants, depriving the leaves and fruit of moisture. They are common in home gardens in the mid to eastern US and may appear in southern Ontario.

Wilting leaves along with holes at the base of your plants that exude a green, sawdust-like substance signals that squash vine borers are present. Once they’ve colonized a squash plant, they can be hard to control, but organic methods include prevention and physical controls.

Signs of the squash vine borer include wilting leaves.

Prevention:

• In the northeast, plant summer squash in early July after adult borers have completed their life cycle and are finished laying eggs.
• Plant butternut squash, which is known to be less susceptible to the pest. Avoid zucchini and other varieties of summer squash, since they are the least resistant.
• Rotate your squash crops, making sure you don’t plant them in beds where cucumbers or melons grew the previous year.
• Cover the bases of young plant stems with aluminum foil to prevent adults from laying eggs.
  Remove and destroy affected plants to prevent re-introducing borers the following year.

Physical controls:

• When your plants are small, sprinkle diatomaceous earth around the base of each plant. Reapply after every rain.
• When your plants begin to vine, cover with a floating row material and secure the sides. (Do this only if you’re sure borers haven’t overwintered in your soil from a previous crop.) Leave in place two weeks before removing so bees can pollinate your plants’ flowers.
• Set traps. Place a yellow bucket or bowl filled with water around your plants. Adult borers are attracted to the color yellow and will fly into the water and drown. Yellow sticky traps are also effective.
• If you detect a borer in your plant, insert a wire up the plant stem to kill the larvae. You can also make a small incision in a plant’s stem to identify and remove the borers, but the plant may die. Bury any cut areas in soil to encourage rooting.

Aphids

Another common garden pest that can feast on squash plants is the lowly aphid. If you haven’t seen aphids before, lucky you. They’re prolific in many gardens and are a common sight on everything from cabbages and kale to the lowly Scotch thistle. Thankfully they’re also easy to see, since they travel in colonies. Watch for a discoloration on plant stems—green, purple, and black are some common aphid hues.

In many cases, aphids will damage a handful of plants before becoming a meal for beneficial insects including ladybugs and wasps. That means you may not need to do anything at all if you see these helpful predators present on your plants and the infestation is not too extensive. Gardens containing a healthy variety of plants and healthy soil can often fend off too much damage from aphids because they attract these natural predators.

If the infestation is getting out of hand, start by spraying affected plant stems with a jet of water. Often this is enough to wipe them out and no more work is necessary. If the situation persists, consider introducing beneficial insects such as the Aphidoletes midge and Aphidius wasp—excellent choices to buy for controlling aphids. Neem oil is also effective at controlling aphids when applied according to product instructions.

Related: An Abundance of Aphids: Natural Pest Control

Squash bugs

Squash bugs attack the leaves of your plants, causing them to wither, blacken, become brittle, and eventually die. The most common squash bug is the Anasa tristis, a harmful pest that ranges throughout Central America, the United States and southern Canada, feeding on squash, cucumber, and melon plants.

Adult (bottom) and nymph (top) squash bug. Photograph by John L. Capinera, University of Florida.

The first sign of squash bug trouble is usually brown marks on the leaves. To pre-empt this problem, examine the undersides of your plants’ leaves regularly. If you spot clusters of oval-shaped brown eggs, remove them. Squash bugs are known to favour larger, more mature squash plants, and earlier plantings are particularly susceptible.

Damage to plant leaves after feeding by squash bugs. Photograph by John L. Capinera, University of Florida.

If squash bugs are already affecting your crop, trap them by placing cardboard or large cabbage leaves on the ground around your plants. The bugs will hide there during the day, and you can gather them up and destroy them. Introducing beneficial insects such as the Trichopoda pennipes may also help reduce squash bug numbers if available in your area.

It’s also important to clean up any spent squash plants after harvest to prevent squash bugs from overwintering in your garden.

Blossom end rot

When the ends of your squash plants shrivel and turn brown, this is usually a sign of blossom end rot. This condition occurs where plants lack calcium, either because they can’t get enough from the soil or because something blocks them from taking it up. To prevent blossom end rot, perform a soil test before you plant to check calcium and acidity levels. Low pH (under 5.5) means that plants will have trouble absorbing minerals from the soil. Treat with lime three months before planting to increase your soil’s alkalinity.

If your soil pH is fine but you still see signs of blossom end rot (and these signs don’t persist throughout the whole growing season), plant stress may be the cause. Drought, wet soils, and unusually cool or hot weather can tax plants and prevent them from absorbing minerals effectively. Do your best to ensure plants receive even watering from drip irrigation or soaker hoses and protect them from weather extremes.

Powdery mildew

When mature leaves have powdery spots on upper and lower surfaces, this is the first sign of powdery mildew. Eventually these spots may grow to form large patches, covering leaves and stems. This fungus can weaken plants, reduce fruit set, and cause premature ripening. Since powdery mildew infections thrive in warm, dry conditions and closely planted crops, be sure to give your squash plants adequate room to increase airflow. If powdery mildew appears, spray leaves with a solution of neem oil and water (2 tablespoons of neem oil concentrate to 1 gallon of water). This will help reduce or eliminate powdery mildew in as little as 24 hours.

Mosaic virus

Squash mosaic virus causes leaves and fruit to become mottled and misshapen. Photograph by MSU Diagnostic Services.

Squash mosaic virus appears as dark green and blistering patches on the leaves. Leaves and fruits become mottled, bumpy, and misshapen. Beetles—including the leaf beetle and spotted cucumber beetle—transmit the virus after feeding on other infected plants. It can also be spread by infected seed. Remove and destroy any infected plants and clean bed of spent plants at end of season. Choose disease free certified seed.

Alternaria leaf blight

Leaf blight on squash begins with small brown spots that may turn black.

This fungus first appears as brown spots on the leaves that later turn black. Fruits become spongy with tough, dry rinds. Since this blight is spread by overwintering plant debris, clean all spent plants from the previous year and practice crop rotation. Avoid overhead watering to keep leaves dry, opting for drip irrigation or soaker hoses instead.

Other common problems

Why are there marks on the bottom of my squash plants?

To protect growing fruit from wet grass and soil, slide a waterproof material like a board, cedar shake, firm plastic piece, or even tar paper squares under each one. Very gently lift the squash so it doesn’t twist or roll (you don’t want to break the stem) and slide piece underneath. This is best done when squash are small and lightweight.

Why do some of my squash shrivel up without maturing?

If you’re seeing a lot of small, soft fruits that seem to give up before getting anywhere, you’re probably seeing a lack of pollination. Squash plants need pollen from the male flowers to make it to the female flowers before they can grow and ripen. If you often lack pollinators in your garden, consider interplanting flowers and squash to attract more varieties. You can also let bee-friendly crops like cilantro, herbs, and kale go to seed before pulling spent plants.

If you’re already mid-season and you notice a lack of bees and other pollinators, consider hand pollinating your plants. The easiest way to hand pollinate squash plants is to use a paintbrush, toothbrush, or cotton swab and gently transfer the pollen from the male flower (which has a long, thing stalk) to the female flower (which has a swollen, budding fruit at its base). Hand pollinating can help increase your yield, even when pollinators are present.

Are there other ways to help fruit ripen more quickly?

To help your squash plants ripen the most fruit possible, begin removing fruits smaller than a baseball in early August. This will help your plants put their energy into ripening fewer, larger fruit and give you the most ripened weight per plant. (You can eat those unripened fruit as if they were summer squash). You can do the same with female squash blossoms, ensuring no more energy goes into producing new fruits that won’t reach maturity. Lastly, around the same time of year, clip the ends off those squash vines two leaf notes past the last ripening fruit. Use only clean, sharp shears.

How to hand pollinate squash plants

Harvesting, curing & storing squash

To cure squash, leave outside in the sun after harvest for 7-10 days. Perfect curing weather will be warm and dry.

The best part! Harvesting squash is the grand finale of all your hard work. Now you can enjoy many months of squash soup and other goodness. Read on for answers to common harvesting questions to get the most from your crop.

How will I know when squash are ready to harvest?

Summer squash can be eaten at any size, but winter squash are more particular. Harvest winter squash when the rind is deeply colored and thick enough that you can’t break it with your fingernail. Make sure you harvest before the first frost, or when you’ve had more than a week of weather below 50 F (10 C). Too much chill will affect how long your squash will last in storage. If all the vines are dead, the squash need to be picked.

What’s the best way to harvest squash?

To harvest squash, cut the fruit from the vine (or bush) using sharp, clean pruners. Leave 2 to 4 inches of stem—and be careful not to break this off. The goal is to jiggle the stem as little as possible since the stem protects the squash from rot and pests and will help it last longer in storage. A broken stem leaves a wound that starts to spoil almost immediately. To prevent breakage, avoid carrying by the stem and handle carefully from the bottom.

How do you ‘cure’ squash for storage?

The beauty of home grown squash is how long it lasts. Some varieties will keep until spring, meaning you can grow your own year-round supply of vitamin rich vegetables. But first they must be ‘cured’ or seasoned. To cure squash, leave outside in the sun after harvest for 7-10 days. Perfect curing weather will be warm and dry. If you’re concerned about frosts or live in a cold climate, place squash in a warm, sunny window and cure for up to 10 days at 80 to 85 F (25 to 30 C).

Can I eat green/immature winter squash?

If you have an early frost or need to harvest immature squash for any reason, they are still edible. While they may not have the rich flavour of a mature squash, they work well in soups, salads, and other dishes. If young enough, you can also eat the skins—just like a summer squash.

Is it possible to ripen green/immature squash after harvest?

Yes, it is possible to ripen squash that you had to harvest before its time—as long as it is somewhat mature and has started to change colour. Remove dirt and debris (washing if necessary) and place in a sunny window. Turn periodically so all sides get equal exposure to sun. Immature squash are more susceptible to fungus and mould, so keep your eye on the fruit as it warms its way to maturity.

Should I wash my squash before storing?

No. Washing mature winter squash isn’t necessary (unless you’re trying to ripen immature squash—see above). Gently rub off excess dirt and store until needed. There is some evidence that dipping in hot water (135 to 140 F) for three minutes helps to sterilize the fruit, but squash must be completely dry before storing or you risk rot and pests. If you do decide to wash, avoid holding by the stem and wipe dry when finished.

What’s the best way to store squash?

If you’ve grown a variety of squash and taken the time to cure them properly (see above), you can have ripe and delicious fruit until spring. Place in a well-ventilated area that maintains a steady temperature of 50 to 55 F (10 to 12 C) with moderate humidity. Don’t pile up, but store in a single layer not touching each other. Avoid storing on concrete floors or with apples and pears.

Since different varieties of squash will keep for different lengths of time, be sure you check stored fruit for any rot or soft spots and rotate regularly. Remove any that need using or store in fridge until you have time to cook them.

Enjoy your freshly harvested (or carefully cured) squash using one of these fabulous recipes.

Sources:

Center for Agriculture, UMass Extension, https://ag.umass.edu/sites/ag.umass.edu/files/fact-sheets/pdf/pumpkins_and_squash.pdf
Clemson Cooperative Extension, College of Agriculture, Forestry, and Life Sciences, https://hgic.clemson.edu/factsheet/cucumber-squash-melon-other-cucurbit-insect-pests/
University of Florida, Entomology and Nematology, http://entnemdept.ufl.edu/creatures/veg/leaf/squash_bug.htm
University of New Hampshire Cooperative Extension
https://extension.unh.edu/resources/files/Resource004198_Rep6024.pdf
Oregon State University Extension, https://catalog.extension.oregonstate.edu/ec1632