Butterkin Squash: Growing the Pumpkin-Butternut Cross in Kansas

Butterkin is what you get when a butternut and a pumpkin are crossed on purpose. The fruit is a flat, scalloped little pumpkin about 6 inches across and 4 inches tall, buff colored, weighing 2 to 5 pounds, and inside it is pure butternut: very dark orange flesh, smooth, dense, and sweet. It is a Cucurbita moschata F1 hybrid, which for a Kansas gardener means the vine borer resistance of the butternut family in a shape that roasts whole and looks like a pie pumpkin on the counter.

What Is Butterkin Squash?

Butterkin F1 (Cucurbita moschata) is catalogued by seed houses as a butternut-class hybrid, and that is the right way to think about it. The plant is a full, vigorous vining moschata, the flesh cooks and tastes like a good butternut, and the rind is that familiar tan. What the pumpkin parent contributed is the shape: flat and ribbed rather than bottle-necked, with a small seed cavity in the center instead of the bulb end. Fruit runs 2 to 4 pounds in most catalog descriptions and up to 5 in good soil, which is a family-size squash rather than a single serving.

Because it is an F1, seed saved from Butterkin will not come back true. What you get in return is a uniform crop, strong vigor, and the sweetness the cross was bred for.

Why It Fits Zone 6b Kansas

Vine Borer Resistance

The squash vine borer (Melittia cucurbitae) needs a soft, hollow stem to tunnel. Moschata squash grow dense, solid stems that borers rarely get through, and Butterkin inherits that from both sides of its parentage. K-State's squash vine borer management guide (MF3309) lists resistant species as the first line of defense; if you have lost zucchini or a pepo pumpkin to borers in July, this is the group to move to. Resistant is not immune. Scout the base of the stems in June and July anyway, especially in a year with heavy moth flights.

Heat and a Long Season

Butterkin wants 100 to 105 days from direct sowing, and moschata types like warm nights. A Kansas summer gives it both. Sown in the first half of May it finishes in late August or early September, which leaves room to cure on the vine before the first frost, typically mid to late October in Zone 6b.

A Pie Pumpkin Shape With Butternut Flesh

Kansas cooks who want pumpkin for pie and butternut for roasting can grow one plant instead of two. The flat shape halves cleanly, the small cavity means more flesh per pound, and the dark orange color carries into a pie without help.

How to Grow It in Kansas

Starting Seeds

Direct sow after the last frost once the soil holds 70 to 75 F, usually the first or second week of May in Zone 6b. Plant 3/4 to 1 inch deep, 2 to 3 seeds per spot, and thin to the strongest. Germination takes 6 to 12 days in warm soil and much longer in cold, wet ground, so waiting a week is cheaper than replanting. If you want a head start, sow indoors no more than 3 weeks before transplant in 3 or 4 inch pots, harden off for a week, and set the plants out without breaking the root ball. Moschata roots resent disturbance.

Spacing

This is a full vining plant, not a bush type. Set plants 3 to 4 feet in-row with rows 6 to 8 feet apart, or plant hills 6 feet apart and let the vines run. Either layout gives each plant roughly 25 to 30 square feet, which is what a full-size moschata needs to size its fruit. In a small garden, train the vines along a fence line or out over the edge of a raised bed rather than crowding them; crowded moschata vines shade each other and invite powdery mildew in August.

Soil and Feeding

Work 2 to 3 inches of compost into the planting area and aim for pH 6.0 to 6.8. A balanced fertilizer at planting, a light nitrogen side-dress when the vines begin to run, then a lower-nitrogen feed at first flower. Mulch once the soil is warm to hold moisture through July. Deep, infrequent watering beats a daily sprinkle; give the plants about an inch a week and more during a heat wave.

Days to Maturity and Harvest

Plan on 100 to 105 days from direct seed. Harvest when the rind has gone fully buff with no green left at the ribs, the stem is corking and drying, and your thumbnail no longer dents the skin. Cut with 1 to 2 inches of stem and never carry the fruit by it. Butterkin will take a light frost on the vine, but bring everything in before a hard freeze.

Curing and Storage

Cure in a warm, dry, ventilated spot for 7 to 10 days, then store at 50 to 60 F with good air circulation. The seed houses do not publish a storage window for this variety, so plan on the moschata baseline of 4 to 6 months and eat any fruit that softens first. For the full method see how to cure pumpkins and winter squash for long storage.

In the Kitchen

Halve it, scoop the seeds, and roast cut side down until the edges caramelize. The flesh is dense enough to cube for soups and curries and sweet enough to carry a pie without extra sugar. Because the shape is flat, a whole Butterkin fits in a Dutch oven for stuffing, and a single fruit feeds a family of four.

Saving Seed

Butterkin is an F1 hybrid. Seed saved from it will grow, but the next generation splits back toward the butternut and pumpkin parents and you will get a mix of shapes and sizes. Grow it for eating. If seed saving is part of your plan, save from an open-pollinated moschata such as Waltham Butternut or Seminole, and read how to save pumpkin seeds for isolation distances.

Related Growing Guides

Start with the butternut squash growing guide for Kansas for the species-wide method, then what is Cucurbita moschata and why it matters for the borer story. If you want the compact version of the same idea, the Butterscotch bush butternut guide covers a 3 foot plant. When mildew shows up in August, the powdery mildew prevention and treatment guide has the plan.

Get the Seeds

Shop Butterkin squash seeds in 10 and 20 seed packets, F1 hybrid and non-GMO, packed and shipped from Newton, Kansas. Browse the full Vine Borer Resistant collection for the rest of the moschata family.