The COVID-19 crisis resulted in store shelves emptied of sanitizers, toilet paper and various staple foods. Seed companies were overwhelmed with orders as the desire to purchase some “food security” drove sales through the roof. Seems like people who previously didn’t think much about gardening were now very interested, and they were seeking the supplies to start their own garden.
Government responses didn’t always make a lot of sense, as was evidenced by the headline, “Buying seeds now prohibited in Michigan — but booze, pot, lottery tickets OK!” The article was accompanied by a photo of a cardboard seed rack in Walmart cordoned off with yellow tape, like a crime scene. I imagined someone leaving the store only to be frisked for seed packets by law enforcement. When I shared that with my son, he replied, “Yeah, but she could just claim the seed evidence was ‘planted’ on her!”
COVID has spurred a resurgence in interest about seed saving, a practice as old as gardening itself. There are many reasons to save your own seed beyond the current limited or delayed availability. Seed saving preserves our gardening heritage and species diversity. It allows us to have more control over our food supply and gardening choices. When we select and save seeds, we can develop better plants that are more productive, more resistant to pests or diseases, and more adapted to our local soils and climate.
Perhaps the best reason to save seed is that it is a deeply rewarding and enjoyable part of the gardening experience. The icing on the cake is that it saves money too. With some basic understanding of plant pollination and seed development as well as mastering the process of collecting, processing and storing seed, you can begin right away to create your own seed bank at home.
Hybrid vs. Open-Pollinated
In nature, plants pollinate each other, mixing their genetics and forming a diverse range of characteristics. In every region, the soil, the climate and other factors exert selection in which the fittest survive. People are often involved in the process too. When a particular superior plant is identified and only allowed to pollinate itself, the gardener is engaged in developing an open-pollinated variety.
Over time, as undesirable offspring are removed, the seeds of such a “stabilized” plant variety, although not genetically identical, are very uniform, producing dependable, predictable results. We have many such open-pollinated varieties in gardening, including the ‘Cherokee Purple’ tomato, ‘Clemson Spineless’ okra and ‘Contender’ bush bean.
Hybrids are created by crossing two genetically different parents — each very uniform in their particular set of attributes — to come up with a new superior variety. Hybrids are usually superior in certain particular aspects to their parents, as well as more productive due to something known as “hybrid vigor.” They can be easily created again and again by crossing those same two parent types.
The problem with hybrids is that you must purchase the hybrid seed to have that specific variety. If you save seeds from a hybrid plant, the offspring will be a varied mix of genetics and thus inferior in terms of the hybrid’s desirable characteristics. Hybrid plants and seed saving don’t mix.
Self-Pollination and Cross-Pollination
Some plants naturally pollinate themselves. Flower form is one reason. Beans and peas are largely self-pollinated, completing the task before the bloom fully opens. So are tomatoes. A tomato’s male and female structures are inside the bloom, where cross-pollination from other tomato flowers is not as likely. While tomatoes don’t need bees to carry pollen from one bloom to the next, bees can play a role in “buzzing” the blooms, causing the pollen to shake loose and fall onto the receptive female stigma inside the bloom. Wind can also shake the blooms and promote better pollination. Lettuce is another vegetable that tends to primarily pollinate itself.
Other plants, however, readily cross-pollinate. Some plants have imperfect flowers in which some of their flowers are only male and others only female. Squash and melons are two examples. Asparagus and hollies, on the other hand, have separate male and female plants. In both cases something must move the pollen from the male blooms to the female blooms. This is where bees and other insects come in. In the case of sweet corn, beets and chard, wind does the pollen transport.
If you want to save seeds from a desired open-pollinated variety, you will want to prevent cross-pollination with other genetically different varieties. This is accomplished by isolating the plant’s blooms. Time is one way to isolate them. Make sure that the variety from which you wish to save seeds blooms at a different time than similar varieties growing in close proximity by staggering the planting times of the two varieties.
Another isolation technique is to space the two varieties a great distance apart. The recommendations for what the safe distance should be may vary from approximately a thousand feet to more than a mile, depending on the species and whether the pollen is spread by bees or wind. Using distance to isolate a variety is not generally practical in a neighborhood, where other gardeners may have other varieties growing at the same time.
Still another isolation option for insect-pollinated plants is to cage the plant. That requires hand-pollinating or placing a few bees inside the cage so all they have access to are blooms from the plant you want to be self-pollinated.
You can also bag the blooms with an insect-excluding fabric and then hand pollinate. Pieces of row cover fabric can be placed over the bloom and tied around the stem (like a lollipop) to exclude insects. I often use organza bags with drawstrings, available in many sizes from craft stores or online. Bagging individual blooms is also great for making intentional crosses, since it allows you to control the pollination process.
Allow seeds to mature before harvesting them so they will be fully developed and viable. Each plant species is different, but if they have structures that dry and release the seeds, allow them to at least begin to dry. At that point, clip them off of the plants and spread them on a screen or newspaper to dry in an area with good ventilation and without direct sunlight.
Some species, such as bluebonnets, propel their seeds some distance, while seed of others, such as lettuce, drift away in the wind. The pods of bluebonnets and some other legumes twist in opposite directions as they dry, so that when the suture between them breaks, the seed is flung far and wide. If you just have a few groups of pods, you should cover them with organza bags or pieces of row cover to contain the seeds. Another option is to place them in a paper bag with a clip holding the top together to contain the projectile seeds.
Species that produce a pulpy fruit (muskmelons, squash, tomatoes, etc.) should be allowed to mature past normal harvest stage so that the seeds are fully developed. Scoop out the seeds and wash them to remove the surrounding pulp and/or gel. Then dry the seeds prior to storage.
Tomato seeds can be cleaned by placing the scooped-out seeds and gel in some water and then allowing them to sit and ferment for a few days. Stir the contents twice daily to prevent mold from forming on the surface of the mixture. The viable seeds will be released and sink to the bottom. After about two days, pour off the pulp and any floating seeds, and then rinse and dry the settled seeds on a screen or cookie sheet for storage.
Proper drying is critical for successful seed storage. Most seed should be dried from the 70–80% moisture level common in developing seeds to about a 5–10% moisture content. Below 5%, the embryo may die. If moisture content is over 10–15%, the enzyme activity in the seeds will continue, rapidly decreasing viability. Increased moisture promotes decay in storage or damaging ice-crystal formation if the seeds are frozen.
Ideal seed drying conditions are cool, dark and dry. Some measures can be taken to speed the process and thereby minimize problems. If you want to get the moisture content of seeds down below 10%, it is best to dry them in air with a relative humidity of less than 50%. A dehumidifier in a small space can make seed drying faster and more effective if you live where humidity is very high.
Seed-drying times vary with temperature, humidity and the type and size of the seeds. Some recommend placing larger seed (such as melons, squash and beans) in a food dryer or oven set to only 100 degrees for 24 hours to speed drying. Others avoid this because overheating can damage seeds. Small seeds tend to dry fine without such added measures.
Perhaps the simplest way to ensure seeds have dried well, is to place them in a container with sachets of a desiccant (such as silica gel) for a couple of weeks. Silica gel is available in craft stores and online. It contains moisture indicators that change color from blue to pink as it absorbs moisture. When it turns pink, simply heat it in the oven to drive off the moisture, indicated by a color change back to blue.
Some folks recommend using powdered milk to dry seeds. While this works, powdered milk isn’t nearly as effective as silica gel and can’t be easily reused.
Nature stores seeds by dropping them on the ground in quantities sufficient to ensure that, if even only a fraction survive, the species can continue. In our gardens we prefer a higher percentage outcome.
Seed storage times vary from roughly one to six years with onions, larkspur and milkweed on the low end, and tomatoes, squash, calendula and globe amaranth toward the upper end. Storage conditions are a bigger factor than species in determining how long you can store seeds.
The keys to maintaining viability in storage are low-to-moderate temperatures and low humidity. While freezing can provide the longest storage times, a refrigerator is fine for home gardeners. Even an air-conditioned room is okay for short-term storage if the humidity inside the storage container is kept low.
Place your dry seeds in an airtight container. Freezer bags are better than regular plastic bags, but a glass jar with a tight sealing lid is even better. Make sure to label the seed with species, variety, date and other such pertinent information. Trust this advice from someone who has more than once thought, “Oh, I’ll remember what that was,” only to find myself staring at a packet of “mystery seeds” months or years later.
Place a packet of desiccant in the storage container to remove moisture, especially that which may form as you open and close the container to access the seeds. Allow containers from cold storage to reach room temperature before opening them, especially if they will be going back into storage, since moisture from the air will condense on the outside of cold objects.
In order save space, each type of seed can be stored in its own labeled paper envelope inside a larger jar. You can make your own paper envelopes or purchase “seed envelopes” online. Some even come ready to run through a printer to create your own unique designs for gifting. I often use coin envelopes (available from office-supply stores) for general-purpose seed storage.
Seed saving is one of the most enjoyable and economically sensible aspects of gardening. I’ve provided a lot of general guidelines for saving “orthodox” seeds, which include most vegetable and flower seeds. There are, however, many exceptions to the various rules. For example, a few species — typically outside of our flower and vegetable gardens and known as “recalcitrant” or “unorthodox” seeds — don’t tolerate being dried down as much or stored in the freezer. Each species has its own specific preferences from pollination to storage. If you want to really get into seed saving, I’d suggest you take time to continue learning about the plants that most interest you. tg