Photo by Seed Savers Exchange
The seeds of each well-loved heirloom cultivar are an unbelievable gift, because within each seed coat are the genes that make that cultivar unique: the incomparable taste of a tomato well-adapted to your community, the unbelievable color or form of a flower given by an old friend, or a superb cultivar purchased through a seed exchange that you hope to propagate for years to come.
Saving seeds from species that are capable of cross-pollination is an exciting challenge for seed savers. Home gardeners who want to save the seeds of cherished heirlooms that fall into this category, such as cultivars of tomatoes and peppers, should look no further than the relatively simple process of blossom bagging. Blossom bagging allows gardeners to grow more than one cultivar of a crop type at a time and save seeds of multiple cultivars in the same season.
Isolate to Propagate
The object of saving the seeds of heirloom cultivars is to maintain and reproduce the qualities of that variety in the seeds that are collected. For species that are primarily self-pollinating, such as lettuce, peas, or beans, keeping a cultivar true to type is relatively straightforward. Cultivars of these species can easily be kept true to type with minimal isolation distance, since plants of this type use pollen from the plant itself, rather than from an external source. This simple process is a good introduction to the practice of seed saving for beginners.
Saving seeds from peppers, eggplants, and tomatoes that are true to type is more complex. They require certain distances from other cultivars to prevent cross-pollination of their flowers. For some plant species, which have flowers containing both the male and female parts, blossom bagging is an option for isolating these flowers from unwanted cross-pollination.
The chosen flower for seed saving is isolated from other flowers of the same species so that it can self-pollinate and produce true-to-type seeds. True-to-type seeds are seeds possessing the desired traits of the cultivar from which they were reproduced. To save these seeds, a gardener isolates a flower by placing it in a blossom bag to ensure that the flower is protected from unwanted pollen from the flower of another cultivar of that species. Bagging the flower isolates it from other cultivars, and also thwarts insects from cross-pollinating it.
However, there are several necessary factors for blossom bagging to work as a method of isolation. The chosen cultivar must have the ability to self-pollinate, and neither have the capability to wind-pollinate, nor solely rely on insect pollination. Research to determine if these two factors are present in your plant. Luckily, blossom bagging works for some of our favorite garden crops: tomatoes, eggplants, and peppers. These crops are prime candidates for blossom bagging because they’re capable of self-pollination. Blossom bagging also works for a number of other flowers and perennials.
Photo by Seed Savers Exchange
Blossom bagging’s purpose is similar to the hand-pollination process, in which a gardener manually transfers pollen from flower to flower. But unlike hand-pollination, the pollination process is self-contained through blossom bagging by isolating a flower that can self-fertilize. The gardener merely contains the flower, and the flower manages the fertilization process itself. For this reason, gardeners often learn to blossom bag certain species before working their way up to the art of hand-pollination.
It’s All in the Bag
Unlike the complex processes for pollinating insect- or wind-pollinated plants, blossom bagging is a simple process. For blossom bagging, individual flowers are contained prior to opening. To ensure the flowers are contained, cover them with pieces of floating row cover and twist ties, craft supply store bags made of fine mesh (often found in the wedding supply section), or pre-made isolation bags sold through seed and garden supply companies. Tightly fasten the bag to prevent insects from entering through the top of the bag, but do so carefully to prevent damage to the plant. If you’re fashioning row cover into a bag, cut it into a circle and wrap it around the flower bud, holding it in place with a twist tie. If you’re using a commercial or craft supply bag, place it over the flower bud and tighten the attached string. Apply these bags to more flowers than you need to save seed from, in case some flowers fail to set fruit and produce seeds.
Once the fruit has set, remove the bag and leave the fruit to mature on the plant until it’s ready for seeds processing. Removing the bag at this point allows the fruit to develop properly, prevents restrictions by the bag, and prevents the containment of moisture and heat that could cause disease. Mark the fruits that have been isolated to easily identify them for seed collection later; relying on memory isn’t an effective method for this process. A colorful ribbon can help draw the eye to the marked fruit and ensure that an isolated tomato isn’t harvested and eaten for supper. Process seeds based on their crop type after harvest: Remove and dry out pepper seeds from their mature fruits; ferment and process tomato seeds; and wet-process and clean eggplant seeds before drying.
Beyond Blossom Bagging
Once you’ve mastered the process of blossom bagging, learning the art of hand-pollination is the obvious next step. And, hand-pollination allows a seed saver to save not only cherished cultivars of tomatoes, eggplants, and peppers, but also squash, cucumbers, and melons, plants that require the process to ensure true-to-type seeds.
Photo by Seed Savers Exchange
Protecting plants from unwanted cross-pollination is a goal shared by both blossom bagging and hand-pollination processes. In each procedure, the gardener facilitates and encourages controlled pollination either by self-pollination or direct intervention. Self-pollination ensures heirloom seeds are true to type, whereas controlled cross-pollination can produce two different results. An heirloom flower cross-pollinated by another flower of the same cultivar produces true-to-type seeds, but an heirloom flower cross-pollinated by a flower of a different cultivar produces seeds with fairly unpredictable traits. This process is breeding, not seed saving. The seeds produced won’t have traits that are stable from generation to generation without a series of grow-outs. Going down this path is what breeders do in creating a new cultivar.
However, cross-pollination within a cultivar can help maintain genetic diversity, and it’s a good thing to promote. We’ll explore this topic further in the Fall 2019 issue of Heirloom Gardener. After all, we heirloom lovers can never have enough seeds of our favorite cultivars. Whether we grow these seeds in our own gardens or share them with others, they connect us to the world and the people and plants that we love.
Try Your Hand at Hand-Pollination
Hand-pollination uses many of the same principles of blossom bagging, but for species that are insect-pollinated. While similar, it’s predominately used for melons, pumpkins, and squashes. To hand-pollinate, isolate the female flowers of a chosen cultivar, which prevents pollination. Then, fertilize the flowers with pollen collected from male flowers of the same cultivar. Finally, protect the fertilized female flowers from any unwanted cross-pollination. This process is used for saving heirloom seeds of pumpkins and melons, but is also used in efforts to breed new cultivars through controlled cross-pollination. The process is complex, but it follows the same principle of excluding unwanted pollen gardeners adhere to when isolating a flower through blossom bagging. There’s no doubt that blossom bagging is the easier approach, but it may lead gardeners to take on the larger challenge of hand-pollination in future seasons.
Photo by Getty Images/burapa
Why Not Insect or Wind Pollination?
Blossom bagging doesn’t work for plants that are solely insect- or wind-pollinated. Isolating a single flower won’t work for cultivars that are solely insect-pollinated. If an insect can’t transfer pollen, fertilization and subsequent seed production won’t occur. It’s possible to isolate and fertilize insect-pollinated species, such as carrots, but this technique requires a cage of mesh or a floating row cover to contain multiple plants. In addition, the gardener must introduce insect pollinators into the cage, a process beyond the scope and efforts of many home gardeners. Isolation is also ineffective for wind-pollinated plants, such as corn, because their fine pollen can pass through barriers, such as mesh and floating row covers, and cause cross-contamination. Isolating wind-pollinated crops by distance to prevent cross-pollination is also complex, because many of these plants require more than a mile of isolation distance from other cultivars of their species.
Photo by Seed Savers Exchange
Lee Buttala is the former executive director of Seed Savers Exchange. He is an Emmy Award-winning producer of “Martha Stewart Living,” and the creator, director, and producer of PBS’s “Cultivating Life.” He is the co-editor of The Seed Garden: The Art and Practice of Seed Saving.