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Seed Saving Basics

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    Posted: 24 October 2012 at 10:58

I’ve been getting a lot of questions, privately, about seed saving. So I figured a primer might serve other gardener’s needs.

Keep in mind that, just as with growing, there are nuances that depend on individual growing conditions.

For instance, most brassicas are biennials; that is, they produce seed the second year. In some areas they can be wintered in the ground. Other places they have to be lifted, stored in a root cellar or something similar, and replanted in the spring.

Beans are normally allowed to dry fully on the vine. But in areas like mine, where the fall humidity can cause in-situ germination, we have to modify that somewhat.

I’m going to post this as a multi-parter. Hopefully, others will have information to add, or questions about clarification. In the end, we’ll have a great seed-saving guide.

It’s important to understand that you cannot save seed, successfully, from hybrid varieties. If you do, the F2 (i.e., next spring) generation will revert to the genetic make-up of the parents. Hybrids are bred from two or more in-bred varieties. So the result will be a group (as many as seven) of “varieties,” none of which resemble the one you were trying to save.

Seed from open-pollinated varieties (which includes all heirlooms), on the other hand, will, in the absence of crossings or mutations, produce plants that breed true to type. That is, the children look and taste exactly like their parents.

When saving seed there are two primary concerns: seed purity, and maintaining genetic vigor. Let’s talk about the second, just to get it out of the way.

Every vegetable variety has a genetic make-up that applies to the community as a whole, but not, necessarily, to each fruit of that variety. This means you have to save seed from enough plants to assure capturing the entire genetic make-up. If not, over time, the plants lose their identity, and, often, become weak, spindly, and tasteless. Old timers describe this as the plant “running out.”

There are specific numbers of plants required to maintain genetic vigor. As a general rule, 15-20 plants will assure capturing the full genetic map. But this depends on the nature of pollination.

Tomatoes, for instance, are naturally in-bred. This means you could, in theory, save seed from just one fruit with no problems. But there’s always that mutation factor to guard against (plant breeders call those unexpected results “sports”). So it’s best to save seed from at least three plants, and five is better. Same applies to most self-pollinating plants.

Brassicas, on the other hand, are out breeders. This means the male flowers on one vine have to pollinate the females on another vine. To preserve genetic vigor, you have to save seed from 30 plants. Which is why most home gardeners do not save seed from cabbages, and the like. Just imagine devoting enough room to grow at least 30 cabbages, for two years, and not even get to eat any of them.

Corn is the worst instance of this. Without going into all the botanical reasons, you have to save seed from at least 100 plants to maintain genetic vigor.

When we get to discussing specific vegetables I’ll put the number of plants in parenthesis just after the veggie type. Like this: Brassicas (30).

There is a simple way to preserve genetic vigor without having to devote an inordinate amount of garden space. Get together with a group of friends. Five or six is a good sized group. Everyone in the group grows the same variety, producing at least five plants. Each gardener saves seed. Then, when the seed is ready to be packaged, you first combine it all, then redivide it.

Seed purity is the big issue. If you’re only concerned with seed for next year’s crop, purity can be less of an issue. If there’s a cross, you won’t get the same variety you planted. But what you get will be edible, maybe even better than the one you started with.

How pervasive is this problem? Several studies have revealed at as much as 80% of home-saved pepper seed is crossed. This results from gardeners wanting to grow more than one variety at a time, without taking proper steps to maintain purity.

On the other hand, if you’re looking to preserve specific varieties, then seed purity is an absolute concern.

There are various methods of preserving seed purity. All of them boil down to preventing cross-pollination; either naturally or by isolation. Let’s explore some of them:

Distance: Distance is the most often quoted method of isolation. And it works fine if you are a commercial seed grower with lots of land. For the home gardener, however, distance is the least useful method of isolation. Why? Because you cannot separate most veggie types. Approved separation distances includes terms like “500 feet,” “a quarter mile,” and even “one mile minimum.” Indeed, even the approved separation distance for tomatoes---5 yards---is difficult for most home gardeners. So, in general, distance is not the best approach.

Intra-species separation: What makes this work is that plants will cross within species, but not with other species of the same type. Primarily this means peppers and squashes in the home garden. There are five species of domesticated peppers, for instance. So, if you insist on growing more than one variety, the trick is to simply grow varieties from different species. Example: You might grow a bell pepper (C.annuum) and a habanero (C. Chinense) side by side, with no fear of crossing.

Caging: Caging is used to either prevent access by pollinators, or to allow them on a careful schedule. Cages are typically built from fine-meshed screening, and completely enclose the plant. An alternative I prefer is to sew draw-string bags from PVA material, making them large enough to enclose the plant on some sort of framework.

Hand pollination and bagging: As the name implies, you physically use a male flower to fertilize a female flower. Then you enclose the fertilized flower in a bag of some sort until the fruit forms. Hand pollination is typically used for squashes, melons, and corn.

Fertility scheduling: This is, perhaps, the least understood method of maintaining purity. It’s based on the idea that different varieties of the same species often are fertile at specific times. If you plant two varieties which are susceptible at different times, then they won’t cross. For instance, lettuces are often fertile for less than an hour after the flowers open. So if you have a variety that opens at 10 in the morning, and another at 3 in the afternoon, they can be planted a couple of inches apart and still won’t cross. Most usually this technique is used for plants that become fertile at different times of the season. You might, for instance, have an early-season corn and a late season corn. By the time the late season corn tassels the early season will be finished.

Physical barriers: Purity can often be maintained in smaller spaces by separating varieties by a physical barrier. This can be an actual barrier, such as a shed, or it can be separating varieties with other plants that are more attractive to pollinators. For instance, you can plant peppers on opposite ends of your garden, and separate them by plants with showy flowers such as okra, melons, or companion plants such as marigolds. Caution: Physical barriers can be the least effective isolation method.

Assuming there is interest in this topic (which I’ll only know if you tell me so), we’ll start looking at seed saving from specific vegetables in the next installment.

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