How to Plant, Grow, and Care for Butternut Squash

Hand harvest butternut squash in the greenhouse plantation
sutiporn / Getty Images

Butternut squash is a sweet winter squash, related to pumpkins and acorn squash, that spreads its vines and broad leaves out in summer and stores sunny energy and antioxidants in its deep orange, late-summer fruit. Like all the winter squashes, it can shade the roots of taller companion plants (such as in a “Three Sisters” garden). The flowers, seeds, and even the leaves are edible, though most people only use the squash itself in a creamy soup, risotto, or butternut ravioli or gnocchi, or as a boiled-and-mashed side dish. The recipe potential is endless, and the squash stores for months until you feel like getting creative with it.

Planting the "Three Sisters"

The "Three Sisters", a term coined by the Haudenosaunee, comes from traditional indigenous knowledge and combines the contributions of squash, beans, and corn. The three seeds are planted together in one hole, in a mound wherever they will get summer rain, or in a deeper hole where there is none — for example, in Hopi farming in the dry Southwest. The broad squash leaves keep the soil cool and may block some weeds. Corn provides a support for bean vines, and the beans fix nitrogen in the soil.

How to Plant Butternut Squash

When planting butternut squash, choose a site where no powdery mildew or cucumber beetle infestations have occurred recently. It is also best to plant winter squashes away from plants that attract the same pests, such as cucumbers and melons. Like most of the vining cucurbits, butternut squash needs some space. You can, however, trellis them, if horizontal space is limited. Good air circulation around plants helps them ward off diseases.

Growing From Seed

Though it is possible to start seeds in trays if your growing season is short, squash seeds are usually planted directly after soil warms up to about 60 degrees F. Shape soil into mounds about four feet apart, and plant two seeds in each, about an inch deep. If you plant more seeds, you will have to thin them. A University of Oregon study found that increased plant density may result in a larger overall number of smaller fruits, so adjust accordingly for your size preference. It may be useful to use plastic mulch for weed suppression and to keep moisture in the soil.

Growing From a Starter

Seeds should be started indoors two to three weeks before planting in warm soil. Transplant following the same guidelines as for direct planting. Harden off the young plants before transplanting, exposing them to outdoor sun and wind for a few hours at first, gradually acclimating them to their growing conditions.

Butternut Squash Plant Care

Squash plants face several pests and disease threats but preparing the soil, maintaining plant health, and being vigilant will pay off in delicious, long-storing squashes.

Light

Winter squash requires full sun.

Soil and Nutrients

According to The Center for Agroecology & Sustainable Food Systems (CFASF), winter squashes such as butternut benefit from a prior winter cover crop and/or the addition of compost to the soil. They prefer acidic, sandy loam soil with good drainage. The CFASF also suggests planting to moisture, a method of soaking beds to flush weeds out and till them back in before planting the winter squash.

Water

At planting time, soil should be deeply soaked, enough so that the plant can grow without additional irrigation for a while. How long depends on the soil’s ability to hold water, whether you have rain, and how much moisture evaporates. This way, the roosts have to reach down deep in pursuit of moisture, while squash leaves grow and create their own weed-suppressing canopy. Drip tape irrigation should keep soil moist, but once the fruits reach nearly full-sized, there is no more need for watering.

On very hot days, leaves may seem wilted, but they are just protecting themselves, so do not overwater. It is also possible to use dry farming techniques (as Hopi, Zuni, and other tribes do) where the soil and weather conditions allow it.

Temperature Humidity

Pay close attention to the days-to-harvest indicated on the seed packet, as the timing of squash planting should start when soil is around 60 degrees F and still allow time for squashes to cure outdoors before rains begin. Adjust for your growing zone, but generally, that means planting between May, June, or possibly July for varietals with a short growing cycle.

Common Pests and Diseases

Spotted Cucumber Beetle on Leaf in Autumn
Spotted cucumber beetle. ErikAgar / Getty Images

Squash pests such as cucumber beetles can damage the plants severely. Squash is susceptible to powdery mildew, which is often spread by insects. Floating row covers prior to bloom may help, and black plastic mulch with a metallic strip, trap crops like buckwheat, and nearby bat houses may help control their population.

Powdery mildew, which commonly affects squash plants, is best prevented, as there is no good solution for it. Affected plants should be removed right away and disposed of properly, or the disease is likely to spread.

Bats to the Rescue

Putting up a bat house near the garden may reduce pests while eliminating your use of toxic chemicals. Bats love to eat cucumber beetles, which fly at night. Bat Conservation International says that, “In one summer season the 150 bats of an average midwestern maternity colony can easily eat 38,000 cucumber beetles, 16,000 June bugs, 19,000 stinkbugs, and 50,000 leafhoppers.”

How to Harvest Butternut Squash

Ripe butternut squash lying on the ground
Ripe butternut squash lying on the ground. Stefan Rotter / Getty Images

Winter squash is ripe when the rind develops its characteristic color and hardens enough to protect the goodness inside, usually around 110-120 days. The National Gardening Association recommends testing with a fingernail and picking those whose rind is not easily dented. Cut at the stem, leaving a few inches. Let the squash cure in a warm, well-ventilated place for several weeks or outdoors in warm weather for about a week. Any that have bruises, dents, or ugly spots should be eaten immediately.

Butternut Squash Varieties

  • Waltham is the standard, full-sized butternut. Heirloom versions are available so that you can collect seeds and plant them again. This type of butternut squash is somewhat susceptible to powdery mildew.
  • Honeynut, developed originally as a hybrid between butternut and buttercup squash, is small, sweet, and more resistant to powdery mildew.
  • Butterbush is a compact plant that can be grown in containers and produces individual-sized squashes.
  • Distinctive heirlooms include the rough-skinned Rogosa Violina and a dark orange-skinned varietal.

How to Store and Preserve Butternut Squash

Researchers in Ghana, where butternut squash is gaining popularity as a highly nutritious crop, found that storing butternut squash off the floor (a pallet works well) at a mild temperature with 76% relative humidity offered the best longevity and could extend the shelf life beyond five months. Properly cured and stored, butternut may last as long as 8 months, well into colder months when a butternut squash bisque is just the perfect meal.

View Article Sources
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  2. Leap, Jim, et al. "Organic Winter Squash Production on California's Central Coast: A Guide for Beginning Specialty Crop Growers." UC Santa Cruz: Center for Agroecology and Sustainable Food Systems, 2017.

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