How to Grow and Care for Winter Squash (Cucurbita Maxima)

Squash is one of three plants in the Native American planting tradition known as "The Three Sisters," which includes beans and corn. Beans offer a natural, nitrogen-rich fertilizer, while the corn provides a natural trellis for the beans if they are of a climbing variety. Meanwhile, the squash can cover the ground quickly and discourage weeds All winter squash varieties require a long growing season from 75 to 100 frost-free days. To give them the time needed to thrive and produce abundantly, sow seeds by late May in northern locations and closer to early July in more southern, warmer states. Harvest squash in autumn just before or just after fruits are fully mature. Skin will not be edible, but the squash will have quite a long shelf life. Some last throughout winter (hence the name "winter squash").

Winter Squash Care

Winter squash seeds germinate well when sown directly into the soil. Plant seeds 1 inch deep, 2 to 3 feet apart. Or, sow 3 to 4 seeds closer together in small mounds (hills) so that the soil remains warmer and drains faster. Arrange the groups in rows about 3 to 6 feet apart. Seeds will germinate in less than a week in a soil temperature of 70 degrees Fahrenheit or higher. In cold climates, it may be necessary to use row covers or protective frames during the first few weeks of spring. Thin seedlings when they reach 2 to 3 inches tall, snipping unwanted plants off the surface while not disturbing the roots of the ones that remain. Leave one plant for every 18 to 36 inches of space.

Be careful not to overplant, as many full-size winter squash varieties require 50 to 100 square feet to spread freely. In a smaller garden, consider planting winter squash at the garden's edge and guide the vine across the lawn. Throughout the growing season, be mindful of the plant's shallow roots and the delicate quality of the vines.

Light

Winter squash prefers full fun.

Soil

Plant in rich, fertile, well-draining soil such as loam. If needed, add aged manure to the planting site (about 50 percent native soil to organic matter) mixing deeply into the top 8 to 10 inches of the soil. Allow it to settle for a couple of weeks before sowing seeds. Maintain a pH between 5.5. and 5.9, though plants will tolerate a pH up to 6.8.

Water

Water well and often. Give plants at least 1 inch of water weekly. If the leaves wilt or plants are established in sandy soils, water more diligently. As fruits form, water frequently. Avoid wetting the leaves and fruit by using a small-mouthed watering can directly on the surface of the soil into the roots. Otherwise, dampness may cause root rot and other diseases.

Fertilizer

Winter squash feed heavily on fertilizer. Before planting, soil can also be enriched with liquid seaweed fertilizer. In addition to mixing organic matter into the soil, aged manure or compost can be mixed into the water to make compost tea. When the plants first start blooming, scratch in about 2 tablespoons of all-purpose fertilizer or a generous amount of a liquid organic fertilizer or organic granular fertilizer around every hill. Avoid getting fertilizer on plants, and water the plants after fertilizing. Feed plants about every 2-3 weeks. As fruits and more flowers come, feed plants a little more.

If you grow just a few plants, apply 2 to 3 tablespoons of a balanced 10-10-10 fertilizer on each hill. Scatter it evenly and work it into the top 3 to 4 inches of the soil. If there is a larger plot, mix in 2 to 3 pounds for every 100 square feet. Protect the shallow roots with mulch to retain moisture and prevent weeds.

Temperature and Humidity

Winter squash seeds will germinate in soil that is between 60 and 105 degrees Fahrenheit. They will not germinate in cold soil so do not sow until all danger of frost has passed and both the air and the soil reach at least 60F. The ideal temperature is 95F.

Types of Winter Squash

The most commonly grown varieties of squash belong to one of three species: Cucurbita pepo, C. moschata, and C. maxima. Winter squash (C. Maxima) include many cultivars such as:

• C. maxima 'Hubbard,' the fruits of which can weigh anywhere between 15 and 49 pounds, while the 'Baby Blue Hubbard' produces fruits that only grow to about 6 pounds. Skin is blue. Flavorful flesh is golden-yellow.
• C. maxima 'Turk's Turban' (pictured above) is also known as French turban and turban squash. Mature fruits usually weigh about 6 pounds. This heirloom is closely related to buttercup squash, which is also a cultivar of C. maxima.
• C. maxima 'Galeux d'Eysines' is a historic French variety from the Bordeaux region. Fruits reach between 10 and 20 pounds each, with a faintly peach color skin and a pimply texture. Harvest fruits when they are slightly immature, as they tend to crack when fully mature.
  
• C. maxima 'Ambercup,' also known as Japanese pumpkin 'Ambercup', is a type of 'Kabocha' squash/pumpkin. Medium green-skinned fruits mature to a weight of 4 to 6 pounds.
  

Pruning

Prune vines to make the most of the space and to concentrate the plant's energy on fruit production.

Potting and Repotting

You can grow miniature varieties on trellises or just about any variety in large 5 to 10 gallon buckets. Support heavy fruit with netting or slings of fabric that is breathable. For vines and fruits grown on the ground, you can place a piece of wood or cardboard underneath a maturing squash to prevent rot and soft spots.

Common Pests and Plant Diseases

Keep an eye out for the following pests: squash bugs, squash vine borer, and striped cucumber beetles. You may also face bacterial wilt, powdery mildew, scab, viral disease, and downy mildew. To prevent early-season pests like squash vine borers and diseases, plant a few squash seeds in midsummer. Row covers may protect plants early on from insects. Remove covers before flowering to welcome insects to pollinate the blooms as the season progresses. Nasturtiums are a good companion plant to help deter the adult version of the squash vine borer which is a red and black moth.