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 is a type of winter squash. The fruits start out with a light green skin, but their skin (shell) turns beige when they are 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 as you would mashed potatoes. A nutritious vegetable ("fruit," technically), it is high in vitamin A.

Botanical Name Cucurbita moschata
Common Names  Butternut squash, butternut pumpkin, gramma
Plant Type Annual
Mature Size Vines become 10 to 12 feet long
Sun Exposure Full sun
Soil Type Rich, well-drained soil
Soil pH 5.5 to 7.0
Bloom Time Summer
Flower Color Yellow
Hardiness Zones Needs a growing season of 60–120 days
Native Area Originally bred in Massachusetts, U.S.

How to Grow Butternut Squash

People who want an instant garden 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.

But butternut squash is so easy to grow from seed, yourself, that most gardeners purchase butternut squash seed packets (available at grocery stores, hardware stores, etc.; also available online and from seed catalogs). Once you have the seeds, there are two possible ways to proceed:

  • Start them indoors to get a jump on the season.
  • Wait until danger of frost has passed and direct-sow outdoors.

Unless you live where the growing season is very short, it is perfectly acceptable to choose the latter option, which requires less work. But if you do wish to get a jump on the growing season, here is what to do:

Obtain some peat pots at your local home improvement store. Fill the pots with potting soil in April and plant 2 butternut squash seeds in each pot. Place the pots in a sunny window and 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 in May, 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. At the end of May, plant the peat pots in the ground. 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.

If you choose to direct-sow, simply skip to the step where you create hills and plant 4 or 5 seeds in each hill, thinning them out later to the 3 best seedlings.

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 avoid rotting. You can place small boards, flat stones, bricks, or straw mulch under them.

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 to it).
  • Thump the fruit with your knuckle; it should be hard. Thumping it should produce a hollow sound.

Light

Butternut squash needs full sun.

Soil

The soil needs to drain well.

Water

Seedlings cannot be allowed to dry out. As the summer progresses and the vines get bigger, your plants will need even more water.

Fertilizer

Butternut squash is a heavy feeder. To stay organic, use compost and aged manure.

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. An unheated basement is an example of a suitable storage area.

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.