Buttercup Squash is a rich emerald green 6-8 inch-wide winter squash that has rich, orange flesh that is slightly sweeter than butternut squash and has a creamy texture. Buttercup looks very similar to Kabocha squash, its peak season also starts in early fall and lasts through the winter. Delicious roasted, in soups, pies, stews, and curries. It is also rich in vitamins A and C, B vitamins, carotenoids, and minerals. Squash is one of the plants grown in the traditional Native American vegetable growing technique called the Three Sisters. The other two plants in the Three Sisters are beans and corn. Each plant had its role in this companion planting tradition. Corn served as a structure for the vining beans to grow up. Squash served as a ground cover to prevent weeds from growing. Beans provided natural fertilizer for all. Also Known As: Kabocha Squash, Japanese Pumpkin, Winter Squash, Buttercup Pumpkin, Hokkaido Squash, Uchiki Kuri, Red Kabocha, Sweet Pumpkin, Orange Squash, Fall Squash. Plant Name: Winter Squash, Buttercup Latin Name: Curcubita maxima Days to Germinate: 7-14 Days to Harvest: 90 Plant Height: 18 - 24 Inches Spread: 4 - 5 Feet Growth Habit: Vining USDA Zones: 3-9 Lifespan: Annual Brand: TomorrowSeeds Sunlight: Full Sun, Partial Shade Pollination: Heirloom, Open-Pollinated GMO: No Fungicide-Treated Seeds*: No Seeds Packed For**: 2026 *Fungicide-treated seeds protect the seedlings from diseases until they are up and growing. Do not eat treated seeds. **Seeds are freshly packed for the growing season of the year listed. Seeds are still viable beyond pack date. Store in a cool and dry location such as the refrigerator or basement to best preserve germination rates. Planting Instructions: Soil Preparation: Choose an area with heavy, well-draining soil that receives at least 6 hours of sunlight each day. Remove weeds, large rocks, and litter from the planting area. Leave small weeds and dead grass, they will enrich the soil when turned under. Spade or till the soil 8-12 inches deep. Loosening the soil will help the plant establish strong roots. Plants grow best in soil with lots of organic matter. You may optionally add fertilizer or organic material such as compost, leaves, or rotted hay to mix into the soil at this point. For small gardens, scatter 2-3 tablespoons of fertilizer evenly and work into the top 2-3 inches of soil for each hill or 2 foot by 2 foot planting area. For larger gardens, scatter 2-3 pounds of a complete fertilizer for each 100 square feet of planting area. Work fertilizer or organic material into the soil and leave the surface smooth. Form rows of soil beds 4-6 inches high and at least 4 feet apart. This formation of ridges will help with drainage. Planting: Buttercup Squash grows best in warm weather. Starting Indoors: For an earlier harvest, you may optionally start planting indoors in containers 2-4 weeks before the last expected frost date in Spring, keeping seedlings at least 70F. Harden off then transplant seedlings outdoors in a sunny location when the soil temperature is above 65F. To transplant seedlings, prepare a transplant hole outdoors in a sunny location. Remove the plants carefully from the pots or flats and set them in the holes, burying some of the stem in the ground. Pack the soil loosely around the plant and leave a slightly sunken area around each plant to hold water. Water the plants after transplanting. Optionally, Train plants to climb a 6-8 foot trellis or fence as they establish. Directly Sowing: If directly sowing Buttercup Squash outdoors, plant in mid-late spring when the soil warms to at least 70F. Fall planting is not typically recommended unless planting in climates with mild winters (USDA Zones 9-11) - plant at least 3-4 months before the first expected frost date - or growing indoors at >70F using supplemental grow lights. To plant, make holes 1 inch deep and spaced 4 feet apart down the rows of raised beds. Plant 2-3 seeds per hole. If choosing to thin to the strongest plant, determine the strongest and healthiest plant, then remove all other plants, narrowing to a single plant per hole. Cover seeds thinly with soil and water after planting. Optionally, Train plants to climb a 6-8 foot trellis or fence as they establish. Planting Depth: 1 inch Within-Row Spacing: 4 feet Between-Row Spacing: 3 feet (trellis) or 8 feet (sprawl) Care During the Season: Watering: Water the plants deeply, soaking the soil to a depth of 6-8 inches, once to twice a week. If there is no rainfall, water 3-4 times a week. Sandy soils may need to be watered more often than heavy clay soils. Mulching around plants can help retain moisture. Weeding: Keeping plants weed-free improves production. If plowing or hoeing, do not dig deeper than 1 inch to prevent from cutting the feeder roots. Fertilizing: Once seedlings are established, 2-3 weeks after germination, you may optionally apply 2 tablespoons of a complete fertilizer around each hole, or 1-2 pounds per 100 square feet, without letting the fertilizer touch the plants. Optionally, continue fertilizing every 3-4 weeks as plants grow, especially after flowering begins. Water plants after fertilizing. Insecticides: Insecticides may be used to protect plants. Bt-based insecticides and sulfur are organic options that can be used for prevention. Sulfur also has fungicidal properties and helps in controlling many diseases. Before using a pesticide, read the label and follow cautions, warnings and directions. Diseases: If spots or mold appear, treat plants with an approved fungicide. Neem oil, sulfur, and other fungicides may be used. When using fungicides always follow label directions. Harvesting: Buttercup squash is ready to harvest when the skin has turned a deep, dark green color, often with orange undertones, and is firm to the touch. The stem should be dry and woody, and the vines often begin to wither and die back. It’s best to harvest the squash before the first frost hits, as a light frost can damage the fruit. Use a sharp knife or pruners to cut the squash from the vine, leaving about 2 inches of the stem attached to avoid injury to the squash and help with storage.
