Seed Saving: How to Save Squash Seeds
By Carol Deppe
“The Resilient Gardener” goes beyond traditional gardening guides and gives readers the tools to be self-reliant no matter what the world throws their way. From global warming and nantural disasters to food allergies and weight control, “The Resilient Gardener” has it covered.
Cover Courtesy Chelsea Green Publishing
In The Resilient Gardener (Chelsea Green Publishing, 2010) scientist and gardener Carol Deppe combines her passion for gardening with newly emerging scientific information from many fields—resilience science, climate change, sustainable agriculture and more. In this book you’ll learn how to garden in an era of unpredictable weather and climate change; grow, store and cook different varieties of her five “key crops”; and keep a home laying flock of ducks or chickens. Deppe didn’t just write this book, she lives the principles in it every day, and you can, too, with her expert advice. In this excerpt from chapter 10, “Squash and Pumpkins,” learn the basics of seed saving and how to save squash seeds.
You can purchase this book from the GRIT store: The Resilient Gardener.
Hoarding Squash Seeds and Pumpkin Seeds
I introduced the idea of hoarding seeds, that is, putting away a long-term, ideally frozen stash of seed of every variety you care about, whether you save seed of the variety or not. I didn’t start out with that policy. I started out, as most seed savers do, simply saving seeds of certain varieties and not others. Since I was actively breeding both pepos and maxes, I had to do lots of seed saving for my breeding projects. I figured I didn’t have to also save seed of the squash varieties that are widely available commercially. As should be graphically apparent, that turned out to be a big mistake. No matter how widely used and available a variety is, we really cannot count upon the commercial supply. I did not actually need to save seed of every variety initially, however. It would have been sufficient if I had simply hoarded some of the good “store-bought” seed of each variety I cared about. Then I could have used the hoard to start saving my own seed of a variety when something went wrong with the commercial lines.
To hoard squash seed we have bought, we often need to dry it additionally. We need to learn how to evaluate squash seed to see whether and when it is dry enough. The way to do this is to shell out some seeds and examine the seed shells and the meats separately. When the seed is dry enough, the shell is brittle, and the meat is also. The meat snaps clean when you bend it instead of bending. Very often, small seed such as is typical of pepos is easy to dry, but people often don’t dry the big seeds from the larger-seeded max varieties well enough. What happens with the latter is that it is easy to dry them to where the shell or whole seed is dry enough to snap, but the meat isn’t. The moisture content is too high. In addition, the moisture from the meat re-hydrates the shell in storage, often enough so that the seed molds if stored at room temperature. So to evaluate the dryness of squash seed, always shell some and test the meats.
Saving Squash Seeds and Pumpkin Seeds
Saving our own seeds is the ultimate act of gardening resilience. It’s also a lot of fun. We can produce seed of much higher quality than what we can usually buy. In addition, by doing selection properly, we can improve each variety and shape it so that it better fits our growing conditions, tastes, and purposes. We can enjoy a glorious bounty of seed. We can over-sow cheerfully, saving ourselves considerable work in the process. We can have seed enough to share, seed enough to give away, and in some cases, even seed enough to sell. Buffalo Bird Woman normally traded a single string of seed ears of corn for a tanned buffalo robe. Seed is valuable. Knowing how to save seed is one of the most valuable of gardening skills. Good seed is the ultimate high-value garden crop.
There are four basic aspects to seed saving. One is just the physical processing of the seed. Many people think of this as the primary aspect. It isn’t. Learning to clean squash and dry squash seed just gets you some seed that will grow some something or other. The squash or pumpkins that result may be nothing like the plant the seed fruit came from; the fruits may not even be edible. The primary aspect to seed saving is controlling pollination so that the seed you save is pure seed of the variety you want.
If I just go save seed from a random squash of, say, ‘Sugar Loaf–Hessel’, from my squash patch, that seed will not be pure SL–H in most cases. SL–H is a member of the species C. pepo. It can be fertilized by pollen from any other plant that is of the same species, that is, any other C. pepo. Nate and I grow several different C. pepo varieties and have breeding projects involving pepos. Bees buzz all over the entire patch. Each flower gets visited by bees repeatedly—dozens of times, in fact. (Flowers do not release their pollen or nectar all at once, and bees are competing with other bees for every little bit.) Some of those bee visits are likely to be by bees that recently visited one of our other pepo varieties. In addition, bees do not honor human property lines. They can also visit the squash patches of neighbors. The fruit and seed that represent crosses with other varieties looks exactly the same as the pure seed.
So, to ensure pure seed of SL–H, we need do one of two things. One option is to grow no other pepo except SL–H. This is generally necessary when we want to produce lots of seed, as for commercial sale. For this to work, we must also be far enough from neighbors who are growing other pepos. If we are far enough from squash-growing neighbors, this means we can grow one pepo, one max, and one moschata without any fear of cross-pollination between the varieties. Only varieties within the same species cross. If I want to sell squash seed and have a relatively isolated garden, I could grow, for example, ‘Sugar Loaf–Hessel’, ‘Sweet Meat–Oregon Homestead’, and ‘Waltham Butternut’ without any fear of their crossing, so as to produce and sell pure seeds of all three and have three different squash to eat.
If I grow SL–H as my only pepo, and my garden is sufficiently isolated from all others, there are still some potential problems. If there is one off-type plant in the lot, its pollen can end up in the seeds of lots of fruits. And you often can’t tell an off-type plant until it’s too late, after the fruits have matured, for example. That off-type might not even be the right variety. It could be a volunteer from prior years, or could have been planted by a squirrel. When I do field-scale seed saving, I plant only where there have been no squash planted recently, and I plant seeds into exact positions so as to be able to identify the gardening contributions of squirrels. (Squirrels often bury excess seeds. Gardeners often leave cull squash and pumpkins out, to the delight of squirrels. Squirrels prefer to bury seeds where it is easy to dig—gardens and compost piles. One winter I fed the squirrels sunflower seeds and cull ‘Sweet Meat’ squash. That spring every garden and compost pile in the neighborhood sprouted volunteer sunflowers and SM squash. I no longer feed squirrels.) Finally, while I can evaluate and select fruits on the best plants in the patch for seed saving, most have been pollinated by pollen from many different plants, and some of the pollen parents might be the worst in the patch. Selection based upon just the female parent is useful, but isn’t as effective as selection based upon both parents.
Most squash-loving gardeners don’t want to be limited to just three varieties, one of each species. We want a glorious cornucopia of colors, sizes, shapes, and flavors. In addition, many gardeners have neighbors who also grow squash. And most gardeners don’t need seed from a field of one variety; they just need enough seed for personal use. So most gardeners forget about isolation distances for squash and instead resort to hand-pollinating. We tape certain squash buds and flowers closed to cut the promiscuous bees out of the equation, and we perform pollination services ourselves in a more continent and controlled fashion. If we hand-pollinate, we can both grow and seed save on as many different varieties as we want of each species. The hand-pollination approach has the advantage that, if there is an off type in our patch that we don’t recognize until after the fruits have matured, it is no disaster. We just refrain from seed saving from the fruits on that plant. We also consult our records and eliminate any hand-pollinated fruits that involved pollen from the off-type parent. We get much more powerful selection when we can select for both the best male and female parents.
Hand-Pollinating Squash and Pumpkins
Squash and pumpkin plants have separate male and female flowers on each plant. Any female flower can be fertilized by pollen from its own male flowers as well as from the male flowers from all other varieties that are of the same species. You can tell the female flowers or flower buds because they have a baby squash on the stem under the flower.
Find male and female flower buds in late afternoon or early evening the day before they are due to open. You can tell these “ripe and almost ready” buds by size and the fact that they are starting to color up. Tape them shut. (You don’t tape earlier, because the buds would grow enough to rip holes in the bud as it expanded against the confining tape.) I use strapping tape. Masking tape doesn’t work as well since it’s wet here in the morning. Ideally, you would like two male buds for every female bud we plan to pollinate. It takes all the pollen from two males to fertilize all the ova and give us the most seed. Using two males also makes it more likely that the pollination will “take,” that is, set a fruit instead of aborting. It’s useful to put a stake with a marker near taped buds so you can find them again easily.
Then you come back the next morning. The big buds we taped would have opened into flowers by then if left unmolested, but the tape prevents that. At some point in the morning, depending upon temperature and moisture, the pollen in the male buds starts “dehiscing,” that is, shedding. (The pollen turns bright yellow, fluffy, and loose, and comes off easily.) Dehiscence occurs slightly later in sealed buds than in open, untaped flowers. So just notice when bees start working the patch, and check out a taped male bud or two to see if they are ready. (It can be as early as 6:00 a.m. here on warmer, drier days, as late as 10:00 a.m. on cool days when I watered recently.) If you wait too long, the pollen drops from the anthers and can’t be easily recovered and used.
Pluck a couple of taped male flowers, take them over near the taped female flower you want to pollinate, and rip the tape (and the end of the petals) off the male flowers and strip off the petals so that each becomes a paintbrush topped with pollen. Then rip the tape (with the end of the petals) off a female flower, and holding a male flower by its stem, gently daub pollen onto all three parts of the female flower’s stigma. Repeat with the second male flower. Retape the female flower (with fresh tape, now somewhat lower down on the petals). Keep an eye out for bees and work fast once you open the taped flowers. Bees are not above diving right into a flower just as soon as you take the tape off. Record both the female and male parent on a piece of surveyor’s tape you loop gently around the vine near the stem of the pollinated female flower. (I number all the plants in the patch with a number based upon row number and position in the row.) When the fruit is ready for harvest, tie the surveyor’s tape around the fruit stem. Hand-pollinations take best when they are on the first few flowers of the season, and on the first flower or two of any particular vine. In addition, these flowers produce the biggest, most mature fruits, which give the biggest, most vigorous seed. In addition, fruits, including hand-pollinated fruits, often abort in very hot or overly dry weather. Later-season hand-pollinations are likely to take only if I strip off all the fruits on the vine that are already developing. On any vine upon which I want a hand-pollination, I strip off all open-pollinated flowers or fruits until I have made the hand-pollination. On those first few flowers on each vine early in the season, in good weather, nearly all my hand-pollinations take. A month later, when each vine has set multiple fruits, close to none of my hand-pollinations take, unless I strip off all preexisting fruit. (Then about two-thirds take.)
How to Save Squash Seeds: Selection
There is actually no such thing as “maintaining” a variety. Every plant picks up mutations every generation. Most of these mutations cause the plant to be more like a wild plant and less desirable as a domestic plant. If we simply save seed without doing any plant breeding, the variety rapidly deteriorates into something much less desirable. Varieties are not very stable. We must breed actively in order to retain their excellent characteristics. That is, to be good seed savers, we must be plant breeders, deliberately selecting what germplasm to perpetuate. The core plant breeding method of seed saving is selection. That is, we select our best plants and save their seed. But what is “best”? This is a question that deserves considerable thought in every situation, and gets down to the core of what we want from a garden in general as well as from any particular variety, what we believe in, and who we are. Most seed savers select rather randomly, often completely by accident selecting for characteristics that are the exact opposite of what they want.
I earlier gave an example as to how starting big-vine squash and pumpkin varieties in pots and transplanting can lead to selecting for slow germination and wimpy growth. Another frequent counterproductive situation is to plant too early, so that all the fastest-germinating seeds that germinate and grow well in cool weather get eliminated by a late freeze. The subsequent patch will consist of plants whose seed took longer to germinate and came up safely after the freeze.
If one plant has the biggest fruits, seed savers often erroneously choose that plant or the biggest of those fruits for seed saving. But that approach can result in selecting for a variety whose flesh is more watery. (It’s easier to make water than food. The bigger-fruited plant may have been producing the same amount of real food but just putting more water into the fruits.) I think there is really no substitute for evaluating the culinary quality of each fruit before we accept it as parent to the seeds we save. This is impossible for commercial seed production but is easy to do in our gardens and kitchens. Generally, we should evaluate all the production of a plant, not just a single fruit. Sometimes a plant makes just one big fruit. We shouldn’t select that fruit unless just one big fruit per plant is what we want.
I like vigorous plants that start well from direct-seeding early in the season. I grow organically. I use no seed treatments. I use no sprays of any kind, even organic ones. In addition, I need plants that can do well under ordinary field levels of fertility, such as can be maintained by using legume cover crops. So I plant that way in order to be able to select for plants that do well under those conditions. I always plant excess seed, at least three seeds for every plant I keep. In cases where I am selecting most actively for germination and cold-growth ability, I may plant a dozen seeds for every plant I keep.
Commercial seed producers run machines through entire fields harvesting the seed in the field. This method of harvesting automatically selects for plants that have bigger seed cavities and more seeds but thinner flesh. It also automatically selects for smaller seeds; the fruits with more but smaller seeds will contribute a larger fraction of the plants in the next generation. The original ‘Sweet Meat’, with its thick, very dry flesh, tiny seed cavity, and huge seeds, has only about 250–350 seeds in a 20-pound fruit (as does my line, ‘Sweet Meat–Oregon Homestead’). Is it any surprise that the commercial industry ended up with a variety with a seed cavity two or three times as big, with much thinner fruit and smaller seeds? That is what they were selecting for.
Seed savers sometimes say they only want to maintain preexisting varieties such as heirlooms, not to do plant breeding or create anything new. However, competent seed saving requires plant breeding. In addition, some varieties are always lost through time, or become unworkable as the plant diseases or human needs and standards evolve. Our ancestors were creators of culture, not just passive transmitters. They created new songs and new learning and new technology as well as transmitted the old traditions. They both created and transmitted crop varieties. We should too.
The essence of selection is to save seeds from the best. Obviously, we do not want to save seed from the worst plant we have. If some or all of its being worst is heritable, we would be selecting for a variety that would be inferior to what we started with. We want, if possible, to be improving a variety. So we want to choose our seed fruits from our best plants. But what is “best”? Clearly, the biggest fruit in the patch isn’t best if it is the only fruit the plant produced. We want plants that are generally productive and that produce fruit of the right size that is true to type. Furthermore, half the genes come from the pollen parent, the “father” squash plant. We would like that plant to be best too. But that is just a start.
Many of the characteristics we care about with squash and pumpkins aren’t apparent until the end of the season or even until after fruits are harvested and opened and tasted. So I usually do several hand-pollinations of several fruits when I want to save seed, recording both the female and male parent on the piece of surveyor’s tape I use to mark each hand-pollination. (Again, as stated before, I number all the plants in the patch with a number based upon row number and position in the row.) Then I evaluate all the plants toward the end of the season, noticing and noting any that weren’t as productive or weren’t what they should be. I also notice any significant differences in powdery mildew resistance (which we always have here late in the season), or anything else noteworthy. I record the plant number with a permanent marker near the stem of each fruit before I harvest. Then I open and taste fruits from relevant plants (those representing plants for which I have hand-pollinations) before making the final seed-saving decision, to make sure they have the appropriate thickness of flesh, flesh quality, and flavor. So a good parent plant must produce a good number of fruits of the right size and shape and type, be vigorous, and be relatively disease free for the variety, and its fruit must have all the culinary characteristics it should have. I usually make several hand-pollinations using different plants, then save seed only from the fruits that had the good female as well as male parents.
Selection is considerably less obvious than one might think. At its best, it reflects our concept of the essential nature of the variety as well as our own values and our own essential nature. I cover various aspects, surprises, and subtleties of selection in much greater detail in my book, Breed Your Own Vegetable Varieties: The Gardener’s and Farmer’s Guide to Plant Breeding and Seed Saving.
Another issue in seed saving is numbers. How many plants should we save seed from? Clearly, if we save seed from just one fruit of one plant, that isn’t enough. Something could go wrong with that one hand-pollination. (Occasionally bees bite into taped flowers late in the season, for example.) In addition, if one parent carried an objectionable mutation, all our seed would be affected. We are usually told to save seed from twenty to one-hundred or more plants, depending upon the species. Twenty is the more relevant number for squash. However, nobody I know does this for squash unless they are selling seed. Especially not with big-vine types. I don’t either, usually. Though I do the equivalent. Basically, I cheat.
There is a trade-off between the total numbers of fruits we keep seed of and our ability to evaluate properly which the best parent plants are. I think it is more important to evaluate and choose the parent plants as well as possible rather than save seed from a larger number of plants and fruits. I’m pretty happy if I get about five fruits representing mostly different male and female parents (say seven to ten different parent plants). However, the next year, instead of using my new seed, I may grow up more of my old seed and get another five good fruits representing a different seven to ten parents. And the following year, I might start with that original seed and get another few good hand-pollinations from the best plants of that year. There is no rule that says you have to do your entire round of seed saving all in one year.
For plenty of varieties, I only grow half a dozen plants per year. I hand-pollinate whichever happen to be ready when I’m doing hand-pollinations. If one or more fruits turns out to be a hand-pollination of a good mother with pollen from a good father, I save the seed. If not, I don’t. I just plant another five the next year. Over a few years, I end up having saved seed for the next cycle from five fruits with somewhat more than five parents. And that is generally good enough, especially if I have a permanent stash of earlier seed I can go back to if it isn’t good enough. This approach allows saving seed from many varieties without doing a lot of work.
I don’t normally combine seed from different hand-pollinations. Every fruit is a separate lot, and I keep all the lots separate. When I plant the seed, I also record the exact lot. That way, if there are any problems, they become apparent. And if one lot is giving me especially nice results, it gets identified.
The biggest, heaviest seed on a plant comes from the biggest, most mature (earliest) fruits. I harvest as outlined in Growing Squash and Preparing Your Harvest. Then comes the after-ripening period. That is, the seed continues to mature and become heavier as it sits quietly in the curing fruit. I let all seed fruits after-ripen for at least a month, even the pepos. If the fruit is less than optimally mature, I give it as long an after-ripening period as possible short of the fruit rotting or molding. (It isn’t practical for large commercial seed producers to store fruit so as to after-ripen seed. This is one reason why it is so easy to hand-produce seed that is much better in quality than commercial seed.)
There are two basic ways to process squash seeds. Most of the time I process the seed from a single squash at a time. I open the squash, remove the seeds and put the halves in the oven, then process the seed. Usually, while the seeds are still attached in clumps I eliminate any areas of immature seeds. Then I loosen the seeds into a bowl of water and rub them with my hands. Usually, they float. (So does the pulp. So I prefer to exclude as much pulp as possible from the beginning.) I scoop the seeds with my hands into a second bowl of water and repeat the process. Sometimes I pour the water and seeds through a strainer and rub the seeds around against the strainer and run tap water through them. Mixing and matching and repeating produces clean seeds.
Next comes the drying. I spread the seeds in a monolayer on a dehydrator tray and set the temperature at 95°F. Now I proceed a bit differently for small seeds and big ones. With small seeds, I dry for about eight hours to one day. After the seeds have been drying a few hours, I come back and rustle them up with my hands so that they won’t stick to the tray when dry. Then I examine the seeds for dryness as already described. If they are dry enough, I seal them into Ziploc bags. (Brands matter. Many cheaper brands are thinner plastic.) Or I put them into a 1/2-pint jar and freeze them.
If the seeds are large, especially if they are huge, such as for ‘Sweet Meat–Oregon Homestead’, some Hubbard varieties, and ‘Amish Pie Pumpkin’, the surface of the seeds may crack if they are dried too fast. For these, after a few hours of drying and the rustling-up step, I turn the dehydrator off or take the tray out for a day. Then I return the seeds to the dehydrator and finish the drying. For the biggest seeds of the biggest varieties, the second stage of drying may take a day or more. It is especially important to break open big seeds and evaluate the meats for dryness, as described earlier.
If you don’t have a dehydrator you can dry seeds in a strainer. I have dried large amounts on a screen in front of a fan. You can’t usually get seeds dry enough to seal into airtight containers or freeze that way, however, unless you have very low relative humidity, such as in a desert environment. (You can store such seeds in paper envelopes. But for long-term storage, you need drier seeds.) However, you may be able to finish off seeds in front of a wood stove or space heater if you want optimal dryness and don’t have a dehydrator. (Some people dry seeds with silica gel. It’s a huge pain, though, and not appropriate for larger amounts of seeds.)
The second way to process seeds is more suitable when we have lots of fruits of one lot we are processing at once. We dump the pulp into a bucket or container of water, work the seeds free of pulp, and then leave the mess to ferment a little. The seeds start off floating along with the pulp. After the seeds sink, drain off the rest of the mess, wash the seeds several times, and get them into the dehydrator right away to dry as already described. It generally takes one to three days for the seeds to sink. You have to watch them and catch them promptly.
Fermentation processing does a better job of eliminating diseases and destroying germination inhibitors than does merely hand-washing the seed. Hand-washed seed often doesn’t germinate well in indoor germination tests, even though it germinates very vigorously outdoors.
More The Resilient Gardener Squash and Pumpkin Information:
Curing Squash for Better Flavor
Squash Varieties for Winter, Fall and Summer
Drying Squash: Using the Sun or an Electric Dehydrator
Growing Squash and Preparing Your Harvest
Perfect Pumpkin Pie Recipe
This excerpt has been reprinted with permission from The Resilient Gardener: Food Production and Self-Reliance in Uncertain Times, published by Chelsea Green Publishing, 2010. Buy this book from our store: The Resilient Gardener.