This is the time of year when many plants are producing seeds that are ripe for collection, so it seems like a good moment to address the common mistakes that novice (and practiced) seed savers can make. The result of these mistakes is either that the seeds fail to germinate, or that, much to the surprise of the gardener, the seeds do germinate but do not look like their parent plants.
Of these two outcomes, the failure of the seeds to germinate is the simpler concept to understand. Different species have different indicators of when their seeds are ripe and ready to harvest. Seeds do not continue to mature once they have been separated from the mother plant. It is essential to collect seeds when they are mature, and the most common mistake gardeners make is to collect seeds too early.
Some seeds are contained within dry fruits. Think of the beans in a mature dry bean pod that were left on the vine until the pod turned brown; of the mature hard seeds of dill (The seeds that we cook with or plant are actually individual fruits that are fused to the seed within and are held on the iconic umbels or flowerheads of dill.); or of the thousands of seeds contained within the capsule of an opium poppy that fall to earth as the capsule splits open. The seeds of all these plants are typically mature when these fruits become hard and brittle.
Some fruits may even shatter and open, dropping their seeds onto the soil to germinate the following season. Poppies are notorious for such self-sowing. Other plants such as tomatoes, peonies or melons hold their seeds in fleshy fruits. In this case, seed maturity is usually indicated by the change in color of the fruit. The seeds of tomatoes are typically ripe when their fruits take on their mature color (red for the most common varieties.) The same is true of melons and squashes. The seeds of these fruits can self-sow as well, either in the garden or in the compost pile, which is often the site of volunteer seedlings of tomatoes or squash that are the result of overripe fruits having being tossed into the compost. By knowing the maturity indicators for each species, a seed-saver knows when to collect and clean mature seeds, which, if properly stored, should germinate when sown the next season.
But will the seeds collected produce plants, flowers and fruits that resemble their parents? This is the question that often stymies seed savers. Gardeners are often intrigued by the self-sown vegetable seedlings that come up in their garden or in their compost pile, and are curious about how these plants will mature. It is possible that these volunteers may be a product of cross-pollination between two varieties – say a “Green Zebra” tomato and a “Brandywine.” The chances of such a cross being made varies from species to species, and this needs to be taken into consideration by a seed-saver.
Because of flower structure (some flowers and plants are either male or female, some are both) and other factors, different species and even different varieties have different chances of resembling their parents. It is the relatively closed floral structure of tomatoes that causes them to be primarily self-pollinating. Although the openness of a tomato plant’s flowers may vary a bit from variety to variety, their anther cones tend to enclose the stigma, minimizing any chance of cross-pollination. Typically, seed-savers isolate tomato varieties from one another, keeping varieties 10 to 50 feet apart, but even without such a distance, it is likely the fruit is the product of self-pollination. Chances of cross-pollination are usually estimated as being below 5 percent for most varieties of tomatoes. This low rate of cross-pollination is why primarily self-pollinating or autogamous species, such as tomatoes, sweet and green peas, lettuces and most beans are ideal for novice seed-savers.
Because varieties of some other species, such as pumpkins, radishes, poppies or columbines, have a greater tendency to outcross (some have no choice but to outcross), the resulting volunteers of these plants have a higher chance of being a cross between varieties. To get these plants to produce true-to-type seeds, it is critical to isolate varieties of the same species from each other, either through mechanical means or by keeping varieties at a sufficient distance from one another to minimize chances of cross-pollination.
Beyond this, if the seeds belong to a plant that was an F1 hybrid, the resulting plants will be more varied than that of an heirloom, open-pollinated variety. F1 hybrids do not produce seeds that are true-to-type. Their seeds are more likely to vary genetically, because the parents of hybrids are genetically wildly dissimilar from one another. Examining this process involves a slightly deeper understanding of genetic inheritance. Put simply, these plants were not created to produce seeds that resemble their parents; they were designed to prevent gardeners from collecting their seeds and growing identical plants. Because of these limitations, the move toward seed independence has taken root. For gardeners interested in saving true-to-type seeds, heirloom plants are the only answer, as their seeds resemble not just their species but the variety itself, provided the pollination of the flower is from a plant of the same variety.
Understanding all of these factors is the most essential step in saving seeds that will be true to their parents. However, there is something also to be said for taking chances. Gardeners who have not controlled pollination might still be interested in collecting seed, or in purposely playing with breeding and crossing varieties, to see what might come up. Any cross that does occur could be of interest, although its fruits may not produce seeds that bear the same characteristics in the next generation. Heirloom or open-pollinated plants have been stabilized over generations to produce seed that is true-to-type from generation to generation. This stability is one reason why we love them, but it is also why we may want to do some breeding work and create more of them. This subject will be explored in next week’s column.
A gardener grows through observation, experimentation, and learning from the failures, triumphs, and hard work of oneself and others. In this sense, all gardeners are self-taught, while at the same time intrinsically connected to a tradition and a community that finds satisfaction through working the soil and sharing their experiences with one another. This column explores those relationships and how we learn about the world around us from plants and our fellow gardeners.