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How to Grow Butternut Squash

Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.

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One of the most versatile winter squashes is butternut squash. It can be cooked and eaten in many different ways. You can purchase it from a local farm stand or, if you have the space, grow it in your own garden.

What is Butternut Squash?

Butternut squash (Cucurbita moschata) is a winter squash that originated in Mexico and Central America. It is related to, and tastes a lot like, pumpkins.

Winter squashes are defined as Cucurbita members that have hard enough skin that they can be stored indoors, sometimes for months at a time. Summer squashes such as zucchini (Cucurbita pepo var. cylindrica) have soft skins. They are perishable and cannot be stored for any length of time.

Winter squashes were spread all over North American by the indigenous peoples. They considered them to be very nutritious . They even buried them with their dead to eat on their journey to the afterlife. The modern butternut squash that we know was developed in 1944 by Charles Legett who lived in Stow, Massachusetts.

Butternut squash is an annual vine that grows 10 – 15 feet long with large leaves. The flowers are yellow and the typical squash flower shape.

Like all squashes, butternut squash has both male and female flowers on the same vine. They are easy to tell apart. The female flowers have a tiny fruit (squash) at the base. The male flowers do not. The male flowers open about a week before the female flowers open.

Both male and female flowers need to be open for pollination to occur so it’s a good idea to have a few vines growing in your garden to make sure that there are male and female flowers open at the same time.

Butternut squash is botanically a fruit although most of us refer to it as a vegetable and cook it like a vegetable. The fruits are tan and pear shaped. They grow 9 – 18 inches long and weigh 1 – 3 pounds. A single butternut squash vine produces 6 fruits in average.

The female flowers have a small fruit at the base of the flowers.

The female flowers have a small fruit at the base of the flowers.

How to Prepare Your Garden to Grow Butternut Squash

Butternut squash requires full sun, 6 – 8 hours, and slightly acidic soil, pH 5.5 – 7.0. The soil should be rich and well-drained. These vines are heavy feeders so you should amend your soil with plenty of compost.

Most gardeners grow their squash in hills because the soil is warmer and drains better. The hills should be 6 – 8 inches tall and 2 feet in diameter. Space your hills 4 – 8 feet apart in your garden.

If you want to plant your vines in rows, the rows should be spaced 6 – 10 feet apart.

How to Start Your Butternut Squash Seeds Indoors

Butternut squash has a growing season of 110 – 120 days. Gardeners who have short summers usually start their seeds indoors. Like all cucurbits, butternut squash does not transplant well. It doesn’t like its roots disturbed so it’s best to use biodegradable pots like peat pots that can be planted directly into your garden.

Start your seeds 2 – 4 weeks before your last frost. Fill the peat pots with potting soil and plant your seeds 1 inch deep. They require a soil temperature of 70°F to germinate. Soil temperature is important. Squash seeds will not germinate in cold soil. A heat mat will help keep your soil warm. The seeds should germinate in about a week.

You can transplant your seedlings into your garden when the soil has warmed to 70°F. In my New Jersey Zone 6 garden, that is at the end of May.

Space your plants 18 – 36 inches apart if you are growing in rows or 2 – 3 plants per hill if growing in hills.

Male flowers have no fruit at the base of the flowers.

Male flowers have no fruit at the base of the flowers.

How to Start Your Butternut Seeds Outdoors

You can also start your seeds outdoors in your garden. In the spring when the soil has warmed to 70°F, plant 4 – 5 seeds in each of your hills, 1 inch deep. The temperature of the soil is important because squash seeds will not germinate in cold soil. The seeds should germinate in about a week.

When your seedlings are 2 – 3 inches tall, thin them to 2 – 3 plants per hill. Thin them by cutting the stems at the soil surface. Don’t pull them up. You will disturb the roots of the remaining plants.

If you are growing your squash in rows, plant the seeds 1 inch deep and 6 – 12 inches apart. When the seedlings are 2 – 3 inches tall, thin them to 18 – 36 inches apart. Don’t pull up the unwanted seedlings. That will disturb the roots of the seedlings you want to keep. Use a pair of scissors to cut the stems at the soil level instead.

How to Grow Butternut Squash

After planting, spread a thick 2 – 3 inch layer of straw mulch around your plants. Don’t let the straw touch the plants. The mulch will help keep the soil moist and discourage weeds from growing that will compete with your plants for sunlight, water and nutrients.

If weeds do pop up, don’t pull them up. You don’t want to disturb your plants’ roots. Instead, use scissors to cut the stems at soil level.

Butternut squash are heavy feeders so you will need to fertilize them every two weeks during the growing season. Start with a high nitrogen fertilizer then switch to a fertilizer that is high in phosphorous when blooming starts.

Your plants will need at least 1 inch of water per week. If hand watering with a hose, use a watering wand which is a nozzle with a long handle so that you can water at the roots of the plant. Squash is susceptible to powdery mildew so you want to avoid getting water on the leaves.

Drip irrigation is the best way to water your plants because the water is delivered at low pressure at the roots.

The fruit is ripe and ready to be harvested when the stem is brown and shriveled up.

The fruit is ripe and ready to be harvested when the stem is brown and shriveled up.

How to Harvest Butternut Squash

It’s very easy to tell when butternut squash is ready to be harvested. Just take a look at the stem that connects the fruit to the vine. If it is brown and shriveled up, the fruit is ready for harvest. Another way to tell if the fruit is ready is to try to sink your thumbnail into the flesh. If it is so hard that you can’t get your nail into it, it’s ready for harvest.

Harvest your squash on a dry day with no rain. Use a knife or pruners to carefully cut the fruit from the vine leaving about an inch of stem attached to the fruit. If you don’t leave that “handle”, your fruit will rot. You want to cut the fruit away from the vine rather than try to pull it off because you don’t want to injure either the fruit or the vine.

Don’t use the “handle” to move or carry the fruit. It will break off very easily and then your fruit will rot. Always move your fruit by picking up the whole thing at once.

How to Store Butternut Squash

Butternut squash needs to be cured before it is stored. Curing refers to the drying and hardening of the outer skin of the squash so that it doesn’t rot in storage. You can cure your squash after harvest outdoors for two weeks if there is no rain. If rain is predicted, cure your squash indoors somewhere where it is warm and dry.

As an added safety measure, after curing rinse your squash with a mild bleach solution of 1 part bleach and 10 parts water. This will kill any fungus or bacteria on the skin of the fruit. Wipe the fruit dry and then place it on racks in a cool, dry place. 50°F to 55°F is ideal.

Properly cured and stored, butternut squash will last up to 6 months.

© 2021 Caren White

Comments

Caren White (author) on March 04, 2021:

A compost pile is the perfect growing environment for butternut squash!

Peggy Woods from Houston, Texas on March 03, 2021:

We had a bumper crop of butternut squash growing out of our compost pile in Wisconsin when we got transferred back to Houston. Since our home had not yet been sold, we told our neighbors to help themselves with that crop. It was amazing to see! Sadly, I don't have room to grow it in our current garden.

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