Winter squash, which includes popular varieties like butternut, acorn, and pumpkin from the Cucurbita genus, provides an excellent opportunity for gardeners to save their own seeds. This practice ensures genetic continuity for a favored variety and reduces the annual expense of purchasing new seeds. Saving seeds allows the gardener to select for the best traits, cultivating a strain suited to their local climate. Proper preparation and storage are necessary to maintain the seeds’ ability to germinate reliably in future seasons.
Selecting Mature and Pure Parent Squash
Winter squash seeds reach maximum viability when the fruit is fully ripe, indicated by a hard rind that resists denting, deep color development, and a dry, corky stem. Unlike summer squash, winter squash seeds are typically mature when the fruit is ready for eating. It is best practice to allow the harvested squash to continue ripening for a minimum of 20 days before seed extraction, as this post-harvest period further matures the seeds.
Genetic purity requires ensuring the parent squash is an open-pollinated (OP) variety, not a hybrid (F1). Squash plants are insect-pollinated, and different varieties within the same species, such as Cucurbita pepo, can easily cross-pollinate. Cross-pollination does not affect the current fruit but results in hybrid seeds for the following season. To prevent this, seed savers must isolate varieties of the same species by a significant distance, or ensure only one variety of each species is grown.
Extraction and Cleaning Methods
The seeds must be carefully extracted and cleaned from the sticky pulp. Cut the squash open lengthwise, and scoop the seeds and surrounding stringy material into a container. The goal of cleaning is to remove the germination-inhibiting substance in the gelatinous coating surrounding each seed. Simply washing and rinsing removes most of the pulp, but a fermentation step is highly recommended for superior results.
Fermentation involves placing the seeds and pulp into a jar with water and allowing the mixture to sit at room temperature for one-and-a-half to five days. The fermentation helps break down the gelatinous coating, kills off certain seed-borne diseases, and improves germination rate. After fermentation, viable seeds typically sink while non-viable seeds and remaining pulp float, allowing the waste to be easily poured off.
Essential Steps for Drying and Curing
The seeds must be thoroughly dried to prevent mold and preserve viability for long-term storage. The cleaned seeds should be rinsed again and spread out in a single layer on a non-porous surface, such as a glass plate or fine-mesh screen. A paper towel is not recommended, as the seeds may stick to the paper as they dry. The drying location must be cool, dry, and kept out of direct sunlight.
The seeds must dry completely, which can take anywhere from a few days to a few weeks depending on humidity. They are considered sufficiently dry, or cured, when they no longer bend but instead snap cleanly when folded. For gardeners in humid climates, a food dehydrator set to 100°F or less can be used safely to ensure adequate dryness. Insufficient drying is the most common cause of seed storage failure, as residual moisture encourages fungal growth and rapid deterioration.
Long-Term Storage and Seed Viability
Long-term storage requires maintaining a cool, dark, and dry environment. High temperature and humidity cause seeds to respire more quickly, depleting their stored resources and reducing their lifespan. The ideal storage environment is one where temperature and humidity levels are consistently low. Airtight containers, such as glass jars, are preferred for storage, protecting the seeds from moisture fluctuations and pests.
Paper envelopes placed inside an airtight container are suitable for very dry seeds stored in a cool location, such as a refrigerator or basement. To prevent condensation, any container pulled from a cold environment should be allowed to reach room temperature before being opened. Winter squash seeds stored correctly can maintain good viability for approximately four to six years. Labeling the container with the variety name and the date of harvest is necessary to track their age.