Acorn squash (Cucurbita pepo var. turbinata) is a popular winter squash known for its distinctive ridged shape and sweet, nutty flesh. Although classified as a winter squash due to its hard rind and long storage life, it shares the same species as many summer squashes. For the home gardener, planting timing is the most important decision determining harvest success, ensuring the vine has adequate time to mature its fruit before the season ends.
The Golden Rule of Timing
Acorn squash is a warm-season crop extremely sensitive to cold, meaning its planting window is dictated by local climate conditions. The first step is to confirm that the danger of the last expected spring frost has completely passed. Planting too early risks immediate damage or death from unexpected cold snaps.
Beyond air temperature, the soil must be sufficiently warm for seeds to germinate and roots to establish. The minimum soil temperature required is consistently above 60°F (16°C), with an ideal range of 65–75°F (18–24°C). Cold soil causes seeds to germinate poorly or slowly, making them highly susceptible to rot.
This heat-loving plant also requires a location that receives full sun, defined as six to eight hours of direct sunlight daily. Planting should only proceed once both the threat of frost is gone and the soil has reached the necessary warmth. These environmental indicators define the earliest possible moment to begin the growing season.
Planting Methods and Their Timelines
Gardeners have two primary options for starting acorn squash, depending mainly on the length of the local growing season.
For direct sowing, seeds are planted directly into the garden soil once the environmental conditions are met. This typically occurs after the last frost date has passed and the soil is consistently warm. Seeds should be planted about one inch deep, often in mounded “hills” spaced three to four feet apart. Mounding helps the soil warm up faster while improving drainage, and direct seeding minimizes root disturbance.
Alternatively, gardeners in regions with shorter seasons may choose to start seeds indoors to gain a head start. The critical calculation for this method is to sow the seeds three to four weeks before the last expected spring frost date. Starting earlier than four weeks is not recommended, as the seedlings can become root-bound before it is safe to transplant them outside.
Acorn squash seedlings are notoriously sensitive to root disturbance, which can lead to transplant shock. Using biodegradable pots, such as peat or coir pots, is highly recommended because the entire pot can be planted directly into the soil. Before transplanting the seedlings to the garden, a process called hardening off must occur to acclimate them to outdoor conditions.
Maximizing the Harvest Season
Once the initial planting is done, managing the rest of the season involves looking toward the fall to maximize the yield. For gardeners who wish to ensure a steady supply, succession planting involves planting a second batch of seeds two to three weeks after the first planting. This staggering results in a prolonged harvest window, with the fruit ripening at different times throughout the late summer and fall.
The latest possible planting date is determined by the “Days to Maturity” (DMT) for the specific acorn squash variety, which typically ranges from 80 to 100 days. To calculate the final safe planting date, you must subtract the DMT from the date of the first expected fall frost. Adding a buffer of about two weeks is wise to account for slower growth due to cooling temperatures or poor weather conditions.
It is necessary to have the acorn squash fully mature and harvested before the first hard fall frost arrives. While mature fruit can tolerate a light frost, the plants and developing squash are susceptible to damage from freezing temperatures. Planning backwards from the autumn frost date ensures the full development of the winter squash and protects the quality of the harvest.