How to Grow Butternut Squash From Seed

Butternut squash is a warm-season crop, so wait until all danger of frost has passed and the soil has warmed to about 70F, or 65F at the very least. In most regions that means late spring to early summer. If you plant into cold soil the seeds sit and rot instead of sprouting, so patience here pays off.

Gardeners in the short-season North can get a head start by sowing seeds indoors two to three weeks before transplant time and laying black plastic to warm the ground. In the South and hotter zones, wait for steady warmth and mulch heavily to hold moisture and stay ahead of squash bugs.

Sow seeds one inch deep directly where the plants will grow. For rows, thin seedlings to 18 to 24 inches apart with 4 to 6 feet between rows. If you prefer hills, drop a few seeds together in mounds spaced 36 to 48 inches apart and thin to the two strongest plants per hill.

Seeds usually germinate in 7 to 10 days once the soil is warm. Give the vines room from the start, because a single butternut plant can sprawl 8 to 12 feet as the season goes on.

Butternut squash likes full sun and steady moisture. Aim for 1 to 2 inches of water a week, watering at the base to keep the leaves dry and lower the risk of mildew. As the fruit reaches full size and the rind starts to harden, ease off on watering so the squash can ripen and cure well.

These are hungry plants. Work compost or aged manure into the bed before planting, and side-dress once the vines start to run. Pollination depends on bees moving between the male and female flowers, so avoid spraying open blossoms and plant flowers nearby to draw pollinators in.

Butternut squash grows better with a few good neighbors. These heirloom, non-GMO companions help pull pests away, invite the pollinators that squash flowers depend on, and make the most of a sprawling patch.

Butternut is ready when the rind turns a solid tan or buff color and is hard enough that it does not dent under a thumbnail. The stem near the fruit will look corky and dry. Most plants reach this stage around 85 to 100 days from sowing.

Cut each squash from the vine and leave 1 to 2 inches of stem attached, since a broken stem invites rot. Cure the harvest in a warm, dry spot for 10 to 14 days to sweeten the flesh and firm the skin, then move it to a cool place where it will keep for months.

Butternut squash is one of the most versatile crops you can store. Roast it in wedges or cubes, blend it into soup, or mash it with butter as a simple side. Its sweet, nutty flesh also works cubed into stews, tossed with pasta, or pureed for pie.

Because it keeps for months after curing, a good butternut harvest can feed your kitchen well into winter long after the garden has gone quiet.

• Squash vine borer: tunnels into the stem base and causes sudden wilting. Watch for holes and frass, and mound soil over the lower stem.
• Squash bugs: cluster on leaves and stems and sap plant strength. Handpick them and their coppery egg clusters, and mulch to limit hiding spots.
• Powdery mildew: shows up as white patches on leaves in humid weather. Water at the base, space plants for airflow, and remove badly affected leaves.
• Poor pollination: flowers drop without setting fruit when bees are scarce. Plant flowers nearby to draw pollinators, or hand-pollinate in the morning.
• Fruit rot: squash resting on damp soil can rot underneath. Slip a board or straw under ripening fruit to keep it dry.