Butternut Squash Plant Profile

Grow this winter squash from seed and enjoy a nutritious harvest

Gloved person holding butternut squash on vine.

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Butternut squash (Cucurbita moschata) is a type of winter squash. The fruit starts out with a light green skin, but its skin, or shell, turns beige when the squash is ready to be harvested in fall. The flesh is dense and rich-orange in color. Some people roast butternut squash and use it in soups, while others boil it, mash it, and serve it in place of mashed potatoes. This nutritious vegetable (technically a fruit) is high in vitamin A.

Butternut squash plants are annuals that grow in almost any climate. They are planted in spring, following the last frost of the season. Their vines grow quickly, but the fruits may not be ready to harvest for three to four months from planting time.

Botanical Name Cucurbita moschata
Common Names  Butternut squash, Butternut pumpkin, Gramma
Plant Type Annual
Mature Size 9 to 18 inches tall, 10 to 15 feet wide (vine length)
Sun Exposure Full sun
Soil Type Rich, well-drained
Soil pH Acidic to neutral (5.5 to 7.0)
Bloom Time Summer
Flower Color Yellow
Hardiness Zones 2 to 11
Native Area Central America, South America
Toxicity Non-toxic

How to Plant Butternut Squash

If you want an instant garden, you can sometimes find butternut squash seedlings for sale in peat pots at the garden center. Peat pots break down naturally when planted in the ground, so there is no need to do any transplanting. Butternut squash also is very easy to grow from seed.

Commonly, gardeners plant butternut squash in groups of three, forming a so-called "hill." Hills should be spaced at least 8 feet apart and should be amended ahead of time with compost, manure, etc. Plant seeds 1/2 to 1 inch deep, in groups of four or five seeds. When the seedlings emerge, thin them to the spacing interval specified for the variety.

When the seedlings are young, they are susceptible to drought (so keep their soil moist) and to damage from slugs and snails. Be sure to take control measures against these pests. Later in the season, Japanese beetles can become a problem. You can dust the leaves with garden lime to discourage them or simply pick them off by hand.

During the summer, butternut squash vines profit from regular watering and fertilizing. As fruits form on the vines, place something under them so that they do not have direct contact with the soil. This will keep them dry and help prevent rotting. You can place small boards, flat stones, bricks, or straw mulch under them.

Butternut Squash Care

Light

Butternut squash needs full sun, ideally 6 hours per day. More time in the sun is fine, provided the plants are not overheated.

Soil

The soil should be rich in organic material, and it must drain well. It can be slightly acidic to neutral, with a pH of 5.5 to 7.0.

Water

Seedlings must not be allowed to dry out. As the summer progresses and the vines get bigger, your plants will need even more water. During hot, dry weather, leaves may wilt on a daily basis but will revive as the day cools. If leaves are wilted in the morning, water the plants right away.

Fertilizer

Butternut squash is a heavy feeder. Start with rich soil, and side dress with organic compost or aged manure in the middle of the growing season. In addition, apply a compost tea or liquid fertilizer at two- to three-week intervals.

Temperature and Humidity

Squash are cold-sensitive and will not germinate unless the soil is at least 70 degrees Fahrenheit. These plants love the sun, but they can overheat. During the hot days of summer, it's normal for the leaves to wilt in the afternoon, then revive after the sun goes down. If your plants are not reviving, try giving them some afternoon shade.

Winter Squash vs. Summer Squash

A "winter squash" is defined as a kind of squash that has a hard enough skin that it preserves well if stored in a cool place. Thus, if you were to harvest one in October, it would keep until December (winter) if stored in a suitable place, such as un unheated basement or root cellar.

Butternut squash is just one of several winter squashes that are commonly grown. Another popular winter squash is Hubbard squash (Cucurbita maxima), which has a gray, bumpy exterior.

In contrast to winter squashes, there are also summer squashes, such as zucchini squash (Cucurbita pepo var. cylindrica). Summer squashes have a soft skin and perish quickly.

Harvesting

Use the color of the fruits to determine when to harvest them. As summer winds down, their skin will begin to turn light beige. They are ready to harvest when that beige color becomes deeper; the skin will often have bronze highlights (and no green streaks) in it when the fruit is ripe. Three other indicators will help you determine maturity:

  • Check the stem where it meets the fruit; it turns a brownish color (as if drying out) at maturity.
  • The skin should have a dull appearance (no shine).
  • Thump the fruit with your knuckle; it should be hard and produce a hollow sound.

How to Grow Butternut Squash From Seed

Most gardeners purchase butternut squash seed packets (available at grocery stores, hardware stores, online, and from seed catalogs). Once you have the seeds, you can start them indoors to get a jump on the season, or you can wait until danger of frost has passed and direct-sow outdoors. Direct seeding in the garden is easier, but starting seeds indoors can be helpful to those in areas with short summers.

To start seeds indoors, plant them about three weeks before the last frost in spring. Fill peat pots with potting soil, and plant two seeds in each pot. Water, and place the pots in a sunny window. Do not let the soil dry out completely. If both seeds in a pot germinate, select the healthiest seedling as the one to keep and pinch out the other.

Now begins the hardening off process. On warm days, set the pots outdoors for a few hours at a time. Bring them back indoors at night. Gradually increase the number of hours that they stay out. This process helps them adjust to the transition from an indoor environment to an outdoor environment. Plant the peat pots in the ground once the soil temperature is at least 65 degrees Fahrenheit and all threat of frost has passed.

If you choose to direct seed, simply skip to the step where you create hills and plant four or five seeds in each hill, thinning them out later.