Seed saving is the art of collecting the seed from your crop and using it in subsequent seasons to grow new plants. Even if you save only small quantities of a few crops, understanding more about the life cycle, breeding tendencies, and botany of your crops will help you manage and care for them more effectively.
Only open pollinated crops will produce seed that is viable and that breeds true to itself. Breeding true means that the plants grown from your collected seed will produce a crop with similar traits (growth habit, disease resistance, taste, etc.) to the parent plant. Even with open pollinated crops, to keep the traits you want, you’ll need to learn about their genetics and how to separate flowering crops by time and distance in the garden.
In general, plants that are grown for their flower, seed, or fruit will be easier to manage as a seed saving crop. If you want to collect seed from crops that are grown for their roots, stems or leaves, the plants must be left in the garden past their typical harvest period so that they can continue to grow, flower, and produce seeds. These crops may triple or quadruple in size by the time a seed crop is produced, so must be given wider spacing in the garden. As they send up flower stalks, support and staking may be necessary to keep them upright to maintain good airflow and minimize pests and diseases.
Seed saving strategies are specific to the species you’re working with, so if you plan to delve deep into the world of seed saving and breeding, we highly recommend picking up a few of the books on the subject. While you’re here, let’s dive a little deeper into the basic concepts of seed saving and plant breeding.
Inbreeding and outbreeding
If you are saving seed with the goal of preserving the varietal traits of your parent plants, you need to understand the reproductive tendencies of the specific crop you are working with. Certain crops have a strong tendency to inbreed. In this context, inbreeding means that the plant pollinates itself (when a single plant has both male and female flowers). This is particularly common in crops with flowers that remain closed during their fertility period. Other crops tend to outbreed, meaning that they share pollen easily with other plants (also referred to as cross-pollination). The plants they share with must be the same species, but can be different individuals and/or varieties. Most crops are not perfectly inbreeding or perfectly outbreeding, but fall somewhere in the middle.
If you want to preserve varietal traits in your saved seed, you need to make sure each crop variety is pollinated by other plants of the same variety. Strongly inbreeding plants are typically easier for a beginner to save seed from since it is relatively easy to make sure the seed breeds true to itself and don’t need much assistance to become adequately pollinated. However, these plants will have less genetic diversity, meaning that the health and quality of the plant is at more risk.
Too much inbreeding can lead to inbreeding depression. This is especially a concern when dealing with the small population size of the home vegetable garden. Just like any other overly bred organism, too much inbreeding can result in low vigor and susceptibility to all sorts of problems. Even in a small sample population, genetic variation is important. Collect seed from a number of different plants (rather than all of the seed from one particular specimen). Even if a few of the plants are smaller or uglier than their neighbors, collecting their seed will help ensure more genetic diversity within the population, making it healthier and more stable over time.
Genetic diversity helps buffer species against decimation by pests and diseases. More variation in the genetic code means it is more likely that some of the species’ offspring will be resistant to varying pests and diseases.
Outbreeding crops will have more genetic diversity, but also are more susceptible to receiving pollen from undesirable plants. For example, if you are growing both broccoli and kale for seed in the same garden, the plants are so closely related (any two vegetables with the same genus and species name will interbreed) that pollen from the kale plant will end up in the flowers of the broccoli if they are flowering at the same time. This may result in a great new variety of brassica, but more often will result in an undesirable cross between the two plants. A reduced level vigor and fitness resulting from this type of cross can be referred to as outbreeding depression. Strongly outbreeding crops need to be isolated from other crops that will cross with them if you want the seed to breed true to its parents.
Isolation
If you wish to maintain consistency and genetic stability in your crop, you will need to isolate it from closely related plants while it is flowering. There are three ways to do this: with space, with time, and with physical barriers. The easiest and most manageable isolation method for the home gardener is to separate similar crops by time.
When properly planned, planting related crops at different points during the season will ensure that they flower and set seeds at different times. This is easiest to accomplish with shorter season crops since you can spread out their planting times without running out of favorable weather.
Longer season crops that are strongly outbreeding will inevitably overlap in the flowering phase may need to be isolated by a large amount of space or physical barriers to reduce the occurrence of cross pollination. These isolation methods can be challenging and even impractical on a home scale, so consider focusing your seed saving attention on strongly inbreeding crops or shorter season crops.
