Seed saving

When are seeds mature?

Individual squash fruits are ready for seed harvesting by 60 days after the fruit is fertilized. Some cushaws continue to improve in taste and nutrition if left on the vine longer.

If frost or other issues force early harvesting, some growers report that seeds continue to develop in storage. A publication from Maine Organic Farmers and Gardeners offers minimum recommended timelines for squash fruit and seed maturation: Harvesting Winter Squash for Flavor and Storage. If your fruit may not have mature seeds yet, consider waiting to process the seeds for a month or two after harvest.

Selecting for what you love

If this is one of your first seasons growing cushaws, you may only harvest a few fruits.

Some growers refer to this stage of an adaptation gardening project as a “seed increase” phase when the grower might plan to save seed from most fruits harvested, even if some seem better than others. In the first year or two of an adaptation project, it’s often best to save seeds from every fruit harvested to maintain as much genetic diversity as possible. In subsequent years with more fruit to choose from, the grower can be more selective.

In the future, with more fruit to choose from, a grower can choose to prioritize saving seeds from the tastiest and earliest fruit, or those plants that are hardiest in their ecosystem, or the plants that have the tastiest or most beautiful foliage.

Regardless of your selection criteria, Going to Seed recommends tasting at least one fruit from any squash plant that you are saving seeds from. Squash flavor can be evaluated either raw, or cooked without butter or seasoning. Winter squash cushaws are often stored for several months before use; how long the fruit can be stored at culinary quality is one of the attributes that is often important when making selections for seed saving.

Maintaining genetic diversity in an adaptive population

If you are planning to enjoy the cushaw fruit as food, you may not be processing all of your squash at one time. You may instead be processing seeds at several points through the winter as you use the fruit in your kitchen.

If you have a variety of mature fruit to choose from, it’s best to not let any single fruit’s seeds dominate next season’s mix. Consider the total number of seeds you want to save and aim for a proportional mix from different fruits. The best fruit should contribute more seeds, and fruit that only met minimum standards should contribute proportionally fewer seeds.

Bear in mind that some fruit will naturally contain many seeds while others will have fewer, which you can determine only by cutting them open to use. It may turn out that a squash with relatively few seeds has a particularly desirable attribute.

Processing seeds

Going to Seed has published a standalone guide to saving squash seeds which offers two overall options depending on your preferences and circumstances. Both the ‘dry’ and ‘wet’ processes can be used with cushaw.

Dry enough to snap

Regardless of the cleaning method, it’s essential that the seeds be very dry before storage. Seeds are dry enough when they snap crisply if bent in half.

Climate, and humidity in particular, is an important consideration for drying seeds. Working Food, in Florida, USA, reports in their seed drying fact sheet that humidity is their biggest obstacle to seed longevity. In that area, where ambient humidity ranges from 50%-100% depending on the season, seeds never reach Working Food’s recommended dryness of 35% or lower via air drying.

Many seed savers use locations near a fan, or on top of the refrigerator, or near a heating or cooling vent, where circulating air helps the drying process. While some guides for seed saving discourage the use of a dehydrator out of concern for accidentally harming the seeds, seed savers like myself in humid climates have found dehydrators generally safe to use.

In Eastern Kentucky, it’s relatively easy to dry seeds during the winter when heaters keep the air dry inside. In Spring and Fall, I sometimes use a dehydrator on its minimum setting of 95 degrees Fahrenheit, a setting I have found to be safe for squash seeds. As part of the report from the ECHO Community seed bank about their humid climate dehydration trials in Thailand, they indicate that 100 degrees Fahrenheit or lower is safe for seeds from most crops.

If you are using a dehydrator to dry seeds for the first time, consider running the dehydrator an hour at a time so you can check the drying progress. In my climate, air-dried seeds typically need about two hours in the dehydrator before going into long-term storage.

Storing squash seeds

Dry seeds are not completely dormant; they still respire at a very low level, consuming resources stored in their tissue. In addition to risking mold or decay, storage at higher temperature or humidity increases respiration, depleting the seed’s reserves and decreasing vigor and viability over time.

Ideally, store dry seeds in a cool, dry space in airtight glass or thick plastic containers, or plastic bags designed for freezer use that are 4 mil or greater in thickness. If rodents, insects and other seed eaters are a problem, glass jars, metal boxes or 5-gallon plastic buckets with tight-fitting lids offer protection.

One tool for humid climates is moisture absorbing desiccant packs, which can be added to long-term storage containers along with the seeds. These packs can be dried out and reused many times. Another article from ECHO Community describes a low-tech approach for vacuum sealing, which can be useful in damp regions.

The Garden Professors published a useful article discussing long-term seed storage in more detail: When Good Seeds Go Bad: How long can you store seeds? The grower’s climate and storage space will determine the methods that work best. New seed savers should check saved seeds regularly to catch problems early.