How to Save Seeds from Biennial Plants

Take your seed-saving know-how to the next level by learning how to keep seeds from open-pollinated biennials, including beets and Swiss chard.

| Summer 2017

We save seeds for many reasons: tradition; the idea of seed sovereignty and not being beholden to seed companies; and ensuring that our favorite cultivars don’t disappear. The most obvious reason for seed saving is that we want more plants. And when it comes to saving our favorite vegetable seeds, more plants mean more food. But some vegetables are easier to bring to seed than others. Self-pollinating annuals, such as lettuce and beans, are the easiest from which to save seed. These are followed by other annual crops, such as tomatoes, pumpkins, or peppers, which may require some level of isolation or pollination management, but other than that are grown similarly to how they’re grown for eating.

Biennial crops (varieties that flower, bear fruit, and set seed in their second season before reaching the end of their life-cycle, such as beets, chard, and many brassicas) are more challenging to grow for seed and require a deeper understanding of botany and the processes that bring plants to seed in the first place. Additionally, biennials grown for seed are brought to a state that we aren’t as familiar with, because we typically harvest these plants in their first year.

Download a custom seed packet template for storing your beet seeds.

Basic Seed Saving

Some principles of seed saving are universal, no matter which crops are being grown for seed. Seeds are the product of the fertilization of a plant’s flowers, which brings about fruit and seed production. Seeds that are true to type (seeds that bear the traits of their parent) can only be saved from open-pollinated cultivars that are isolated from cross-pollination with other varieties within their species. This can be confusing because some species contain more than one crop type, and the flowers of these plants can cross with one another if they’re in bloom at the same time. Cabbages, collards, cauliflower, European kales, kohlrabi, broccoli, and Brussels sprouts are all members of the same species, Brassica oleracea. Beets and Swiss chard are also forms of the same species, Beta vulgaris. If different varieties of these plants are in flower at the same time, they can easily cross-pollinate and produce seeds that will not be true to type, or characteristic of their variety. Additionally, some of these crops are self-incompatible, meaning that the pollen from a separate, genetically distinct plant of the same variety must fertilize its flowers to produce true-to-type seeds. In this case, more than one plant has to be grown, although growing a larger population of plants is always a good thing because it helps to maintain genetic diversity.

The cole crops of B. oleracea have an added complication in that some of the crop types within the genus are annual and flower in their first season, while others are biennial and flower after overwintering. If growing these for seed, you’ll need to make sure only one variety within the species is in flower at a time to prevent cross-fertilization. Whatever the crop, in order to flower and bear seed, biennial plants must reach a certain size (reproductive growth is typically possible after plants have eight or more true leaves) and then be exposed to a certain amount of cold for a period of time to trigger flowering and subsequent fertilization. This cold treatment is known as “vernalization” and is critical in bringing biennial crops to seed. The difficulty of this process is that the proper vernalization temperatures need to occur for a cumulative (non-consecutive) length of time without temperatures getting so cold that they damage the crop. In some areas, this is done by creating the necessary conditions in a managed way — by digging plants, potting them up, and storing them in a cold cellar or garage; or by digging roots of some crops, such as carrots and beets, and storing them in a refrigerator so they’re exposed to the cold they need without being damaged by temperatures that dip low enough to damage the plants. In some regions of the country, these conditions occur naturally while the plants are still in the ground, making the whole process much easier to manage.

It’s important to remember that these plants need to reach a minimum size and maturity before vernalization so they’re able to set seed in the second season, and this usually involves having eight or more leaves in the first season or a stem that’s about 1/2-inch in diameter. Surprisingly, younger plants are often better adapted to surviving winter than larger plants, so seed savers will often direct sow or set them out in summer to attain the ideal size before the plants are ready to be overwintered.

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