Butternut Squash Planting Guide: Tips on How to Grow Butternut Squash Plants

Butternut squash (Cucurbita moschata), a winter squash, is a warm-season curcurbit harvested in fall. It is beloved for its sweet and nutty flavor and long storage life, often lasting deep into the winter months. A vigorous grower, this vining plant can yield a bounty of fruits when given plenty of sun, warmth, water, and room to grow.

Growing butternut squash does require some planning. The vines can spread up to 15 ft. (4.5 m), and the crop takes significant time—about 110–120 days from seeding to maturity. In short-season areas, starting seeds indoors can give plants a head start.

Once established, butternut squash is relatively straightforward to grow in a vegetable garden. Give the plants a sunny location, rich, well-drained soil, regular watering, and enough space for the vines to spread, with the ultimate harvest coming before a hard frost.

Quick Butternut Squash Facts

What is a Butternut Squash?

Butternut squash is a type of winter squash harvested after the fruit reaches maturity and the rind becomes thick and hard. Unlike summer squash, winter squash can be stored for months after harvest. Butternut squash is commonly baked, roasted, grilled, stewed, stuffed, baked or mashed.

Butternut (Cucurbita moschata) is one of the cultivated New World species of squash. It has been grown for thousands of years and was brought to market in the 1940s after a Massachusetts grower fine-tuned the variety on his farm.

Types of Butternut Squash

Several butternut squash cultivars are available to home gardeners depending on the size of the squash you’re looking for. Some of the more popular choices include:

• ‘Waltham’: A popular heirloom cultivar with large fruits averaging 4–5 lbs. (1.8–2.3 kg) that can keep in storage for several months.
• ‘Atlas’: This variety produces larger fruit than Waltham and offers a good yield per square foot.
• ‘Butterbaby’: This is a smaller-fruited cultivar for gardeners looking for a more compact option in limited growing space.
• ‘Butterscotch’: This is one of the smaller-fruited cultivars, producing squashes weighing about 1–2 lbs. (0.45–0.9 kg).

Burpee.com has a selection of butternut squash seeds, including the above-mentioned ‘Waltham’ and ‘Butterbaby’.

Planting Butternut Squash

Butternut squash is a summer-loving crop, needing warmth, sunlight, and plenty of growing room. The plants are extremely sensitive to cold temperatures, so wait until frost danger has passed and the soil has warmed before sowing seeds direction in the ground or planting transplants outdoors.

When to Plant Butternut Squash

Even though it is a warm-weather crop, you can get a jump on the growing season by starting butternut squash seeds indoors about six weeks before the last expected frost. Grow the seedlings in a sunny window , under grow lights or in a greenhouse and transplant them outdoors after all danger of frost has passed, being sure to acclimatize them first.

You can also direct-sow seeds outdoors in late May to early June, depending on your local climate. Wait until the soil has warmed to about 60–65°F (15–18°C). Butternut squash seeds germinate only in warm soil, and young plants can be damaged by even a light frost.

Best Soil for Butternut Squash

Sow seeds or plant seedlings in a rich, well-drained soil amended with compost. Butternut squash are heavy feeders so be sure your soil can support vigorous growth and fruit production. If you suspect drainage is a concern and your soil may become waterlogged, plant your butternut squash in a mound or raised bed.

Light Requirements

Choose a location that receives at least 6–8 hours of direct sunlight each day. After transplanting, continue to keep the planting area weed free so the vines have good access to light.

How to Plant Butternut Squash Step-by-Step

Follow these steps to ensure your butternut squash crop has a successful start:

1. Choose the right location. Select a sunny site with rich, well-drained soil. Butternuts love to spread their vines, so choose a space with plenty of room—at least 50 sq.ft. (4.6 sq. m) of growing space per planted hill.
2. Prepare the soil. Draw the soil into a hill or mound about 18 inches (46 cm) high. Mounding helps the soil warm around the seeds and roots and improves drainage.
3. Wait for warm conditions. Plant outdoors only after the danger of frost has passed and soil temperatures reach about 60–65°F (15–18°C).
4. Sow seeds or transplant seedlings. Direct-sow 3–4 seeds per hill. If transplanting seedlings started indoors, harden them off gradually over about a week before planting them outdoors.
5. Space plants properly. Space hills 24–36 inches (61–91 cm) apart, with rows 5–6 feet (1.5–1.8 m) apart.
6. Thin seedlings. When seedlings are about 6 in. (15 cm) tall, thin the weakest plants, leaving three plants per hill. After the first true leaves appear, thin again so each hill has the two strongest plants.
7. Water thoroughly. Keep the soil moist but not soggy as seeds germinate and plants become established.
8. Mulch and monitor the moisture. Mulch around plants to conserve moisture and suppress weeds, and continue monitoring soil moisture throughout the growing season.

Butternut Squash Care

Once established, butternut squash will need to be maintained with adequate watering, feeding, weeding and pest control to help support a healthy crop.

How Often to Water Butternut Squash

Provide about 1 in. (2.5 cm) of water per week. Water deeply enough to moisten the soil 8–10 in. (20–25 cm) down. Keep the soil consistently moist, but not soggy. Avoid the rollercoaster conditions of dry and then excessively moist soils that can happen with infrequent watering.

Fertilizing

Butternut squash are heavy feeders. Fertilize with compost tea or a liquid fertilizer every 2–3 weeks. You can also side-dress plants with compost or aged manure midway through the growing season. Because squash roots are shallow, cultivate carefully by hand or with a hoe and avoid digging deeply around the plants when adding granular fertilizers or compost.

For container-grown plants or gardens that need supplemental feeding, a vegetable fertilizer such as True Organic 4-5-6 Tomato & Vegetable Plant Food available at Target can provide additional nutrients during the growing season.”

Mulching

Apply organic mulch such as shredded leaves around the plants to conserve soil moisture and slow weed growth. Mulch also helps protect the shallow roots from drying out too quickly.

Support

Butternut squash vines can be trained to grow vertically, which can help save garden space and improve air circulation around the foliage. If you choose to trellis your plants, use a sturdy support made from heavy-duty fencing, mesh, or another strong material and install it before the vines become large. Gently guide the growing vines through the support as they lengthen.

Because butternut squash can produce relatively large, heavy fruit, vertical growing is best suited to smaller-fruited cultivars. Larger squash should be allowed to grow along the ground rather than placing their weight on a trellis.

If fruit is growing on a trellis, check it regularly to make sure developing squash aren't becoming trapped between the openings in the support. A sturdy structure is essential because the weight of mature fruit can pull down or topple an inadequate trellis. This Costway 75-in. Garden Trellis available at Home Depot is just the support that developing butternut squash need.

Pruning

Butternut squash vines can become very large. If space is limited, pruning can help control vine size and allow the plant to focus its energy on fewer fruits. Choosing a smaller cultivar is another option for gardens with limited space.

Harvesting Butternut Squash

Butternut squash takes about 110–120 days to mature. Knowing how and when to harvest will give you the best fruits. Pick the fruit when the rind is hard and the fruit has turned a deep, solid tan. Press a fingernail gently against the skin; if it does not leave a mark, the squash is ready.

Be sure to harvest before a hard frost. Cut the fruit from the vine with a sharp knife, leaving a little “handle”—about 2 in. (5 cm) of stem—attached. Use a sharp pair of bypass pruners, such as these Ace 6-in. Stainless-Steel Bypass Pruners from Ace Hardware, to make a clean cut when harvesting squash from the vine.

Curing and Storing Butternut Squash

After harvesting, cure butternut squash will allow it to last for months. Curing allows the skin to harden further and can improve storage life. To cure, in a warm, place the squash in a dry area for one to two weeks. After curing, store the squash in a cool, dry, dark location around 40–50°F (4–10°C). Properly cured squash can keep for several months.

Propagating Butternut Squash

Butternut squash is grown exclusively from seed. Gardeners can direct-sow seeds outdoors once the soil is warm enough or start seeds indoors in last winter about six weeks before the last frost. If you start seeds indoors, harden the seedlings off gradually before transplanting them outdoors.

Butternut Squash Problems

Like many squash crops, butternut squash can be affected by pests, diseases, and cultural problems. Nipping these problems in early stages is best done by regularly inspecting all parts of the plants and developing fruit.

Pests

Butternut squash can attract several insect pests, although healthy, vigorous plants can often tolerate some feeding damage. These are the ones to look for:

• Aphids: Aphids are small, soft-bodied insects that feed on plant sap. They may cluster on the undersides of leaves and around tender new growth. Larger infestations can weaken plants and cause leaves to curl, yellow, or become distorted. Aphids also produce honeydew, a sticky substance that can encourage the growth of sooty mold.
• Beetles: Several types of beetles may feed on squash plants, chewing holes in leaves and damaging young plants. Check plants regularly for beetles and feeding damage, particularly when plants are young and most vulnerable.
• Squash bugs: Squash bugs feed on plant sap and can cause leaves to wilt, yellow, and eventually turn brown. Look for the insects and their eggs on the undersides of leaves, particularly during the growing season.
• Squash vine borers: Squash vine borer larvae tunnel into squash stems, disrupting the flow of water and nutrients. Affected vines may suddenly wilt even when the soil is adequately moist. Check stems for small holes or sawdust-like material, which can indicate the presence of borers.
• Slugs: Slugs may feed on young leaves and developing fruit, leaving irregular holes or ragged areas of damage. They are most active in cool, damp conditions and at night.
• Spider mites: These tiny pests feed on plant sap and can cause leaves to develop a stippled or speckled appearance. Heavy infestations may cause leaves to yellow, dry out, and drop prematurely. Look closely at the undersides of leaves for the mites and their fine webbing.

If pest pressure becomes severe, insecticidal soap can be used to help control some soft-bodied pests. Bees and other pollinators are essential for squash production, so avoid spraying insecticides when pollinators are active.

Diseases

Butternut squash can be affected by several viral and fungal diseases. Good air circulation, proper watering, and regular monitoring can help reduce problems. These are some of the diseases to watch for:

• Squash mosaic virus: This viral disease can cause mottled or mosaic-like patterns on squash leaves. Infected plants may have distorted leaves and produce fruit that is misshapen or has an unusual color pattern. There is no cure for plants infected with a virus, so remove affected plants to help prevent the disease from spreading.
• Cucumber mosaic virus: Despite its name, cucumber mosaic virus can infect a wide range of plants, including squash. Infected plants may develop mottled, distorted leaves and produce poorly formed fruit. Remove severely affected plants and control insect pests such as aphids, which can spread plant viruses.
• Powdery mildew: Powdery mildew appears as white, powdery growth on the surfaces of leaves. The disease is more likely to develop when foliage stays dry but humidity is high. Severe infections can cause leaves to yellow and decline prematurely.
• Downy mildew: Downy mildew causes yellow or pale green spots on the upper surfaces of leaves, often with fuzzy growth developing on the undersides. The disease can spread quickly under cool, moist conditions. Remove severely affected foliage and provide good air circulation around plants.
• Scab: Scab can cause rough, corky, tan or brown lesions on squash fruit. The disease can also affect leaves and stems. Avoid overhead watering and give plants adequate space to improve air circulation.
• Wilt: Wilt diseases can cause squash plants to suddenly wilt even when adequate moisture is available. Affected plants may decline rapidly. Because several problems can cause wilting, inspect the stems and roots and look for other symptoms before removing the plant.

Cracked or Splitting Fruit

When butternut squash shells split, it feels like such a letdown, as the fruit was just so close to the finish line! Splitting usually occurs when a mature fruit experiences a sudden burst of growth after the outer shell has hardened. Heavy rain or excessive irrigation is a common cause. Excess nitrogen and leaving fruit on the vine too long can also be factors. Cracked squash may still be edible if the damaged area has healed and the fruit shows no signs of rot. Of course, it is does show signs of rot, discard the fruit.

Growing Butternut Squash in Containers

Butternut squash can be grown in containers. For best results choose a compact, small-fruited variety rather than a vigorous, full-sized type. ‘Butterscotch’ is a good choice for containers. This compact variety produces 1-2 lbs. fruits on shorter vines and has some resistance to powdery mildew.

Choose a large container with good drainage and fill it with rich, well-drained potting mix. A vegetable-focused mix such as Back to the Roots Potting Mix available from Lowe’s provides a ready-to-use growing medium for vegetables grown in containers. Plant one squash plant per container and place it in a location that receives full sun. Provide a sturdy trellis or other support if you want to train the vines vertically, or allow the vines to trail over the sides of the container. Keep the soil consistently moist and fertilize regularly during the growing season, since plants in containers have limited access to nutrients and water.

‘Butterscotch’ matures in about 100 days and produces several small squash per plant, making it a practical option when garden space is limited.

Growing Butternut Squash Indoors

Butternut squash is not well suited to growing indoors. The plants need full sun, substantial growing space, and room for their long, vigorous vines to spread. They also depend on bees and other pollinators to transfer pollen from male to female flowers, which can be difficult to provide indoors.

Gardeners can start butternut squash seeds indoors about six weeks before the last expected frost, but the seedlings should be transplanted outdoors once conditions are warm enough. Growing the plants indoors for their entire season is generally impractical unless you have a very large, sunny growing space and are prepared to hand-pollinate the flowers.

Companion Planting with Butternut Squash

The best companion plants for butternut squash include flowers that can trap pests, legumes for adding nitrogen, and herbs that attract pollinators. The most beneficial companions plants for butternut squash include:

• Nasturtiums: Act as a trap crop to draw aphids, squash bugs, and cucumber beetles away from your squash vines.
• Bush or pole beans: Fix vital nitrogen in the soil to feed heavy-feeding squash plants.
• Borage: Produces star-shaped blue flowers that attract high numbers of bees to ensure proper squash blossom pollination.
• Marigolds: Emit a strong scent that helps deter pests and reduce harmful root-knot nematodes in the soil.
• Radishes: Plant early around squash mounds to break up compacted soil and harvest before squash vines spread out.
• Dill and oregano: Attract beneficial predatory insects like lacewings, hoverflies, and ladybugs that feed on common squash pests.
• Corn: Provides vertical structure and partial shade in hot summer weather as part of the traditional Three Sisters planting method.

Avoid planting these plants crops near your butternut squash:

• Potatoes: Compete heavily for the same soil nutrients and increase disease susceptibility.
• Fennel: Releases chemical compounds that stunt or inhibit the growth of nearby garden vegetables.
• Other cucurbits (melons, cucumbers, zucchini): Crowding them together increases competition and amplifies pest and disease pressure.

Butternut Squash Growing Essentials

• Looking for a good variety of butternut squash seeds? Burpee.com has a selection of butternut squash seeds, including the above-mentioned ‘Waltham’ and ‘Butterbaby’.
• If you wish to grow your butternut squash plant in a more vertical direction, a sturdy structure is essential for supporting the weight of mature fruit. The Costway 75-in. Garden Trellis available at Home Depot is just the support that developing butternut squash need.
• For container-grown plants or gardens that need supplemental feeding, a vegetable fertilizer such as True Organic 4-5-6 Tomato & Vegetable Plant Food available at Target can provide additional nutrients during the growing season.
• When harvesting, use a sharp pair of bypass pruners, such as these Ace 6-in. Stainless-Steel Bypass Pruners from Ace Hardware, to make a clean cut and leave a small "handle" at the top of the fruit.
• Choose a large container with good drainage and fill it with rich, well-drained potting mix. such as the vegetable-focused Back to the Roots Potting Mix available from Lowe’s.