Autumn is the main season for harvesting seeds from your garden: vegetables, annuals, perennials, shrubs, vines, etc. You can collect the seeds of almost any plant that blooms, but it goes without saying that if you want to harvest its seeds, you mustn’t deadhead the plant (remove its faded flowers), because seeds form on the spot where the flower formerly was.
Why Harvest Seed?
Well, for the savings, of course! Why pay to buy fresh seeds when you can produce your own? This is very obvious with plants you normally would grow from store-bought seed each spring (annuals and most vegetables), but actually you save even more money if you collect and sow seeds from plants that you usually buy already growing (perennials, shrubs, etc.). You can produce hundreds of arborvitaes, rudbeckias or oriental poppies, for example, for what it would cost to purchase a single nursery-grown plant! Your only costs will be for a bag of potting soil and a few pots!
Also, collecting seeds is simple to do and storing them doesn’t even require much space. Plus — and I really have to stress this! — starting your own plants from seed you harvested yourself is immensely satisfying. You’ll really feel you’ve accomplished something when you bite into a tomato you grew from seed harvested the year before!
How to Collect Seeds
There are multiple ways for plants to produce seed, but it’s easiest to look at them as having either dry capsules or fleshy fruits.
Harvesting seeds that are already dry is particularly easy. The seed will be contained in some kind of capsule, pod or husk at the tip of the flower stem. When the capsule or flower head turns brown, it means the seed is ripe. Just cut off the stem below the head or pod. Now open it with your fingers to extract the seeds or, if the capsule opens on its own, turn it upside down and shake the seed out onto a sheet of white paper (that way even fine seed will be easy to see). Or just drop the capsule in a paper bag or some other container and wait a few weeks: it will then open all on its own and drop the seeds into the bottom of the container.
However, some dry seeds are spread by the wind (the dandelion is the best known example) and have parachutes, feathery hairs or other devices designed so they can float away on the slightest breeze as soon as they ripen … often faster than you can collect them. And others have capsules that burst open forcefully and launch the seeds far and wide (think of impatiens, for example) before the capsule even changes color.
For any seeds that are likely to escape before you have time to harvest them, it is wise to cover the flower with a mesh bag just after it fades. This will keep the seeds under control … and the bag will also protect the seeds from hungry birds.
When you do collect wind-borne seeds, it’s best to remove the parachutes or hairs before you store them.
Other seeds are found inside fleshy fruits. This includes most tree fruits (apples, cherries, oranges, etc.), as well as small fruits (blueberries, raspberries, currants, etc.) and quite a number of vegetables (tomatoes, squash, bell peppers, etc.). The fruit will usually tell you its seeds are ripe by changing color, going from green to red, orange, yellow, brown,
Tree fruits and berries are usually harvested fully ripe, making seed harvesting a snap. For culinary purposes, though, gardeners harvest most fruiting vegetables, like cucumbers, summer squashes, and beans, while the fruit is still immature. If so, the seeds inside will most likely still be immature as well. If you want to collect viable seed from these vegetables, it’s important to let their fruits mature fully, leaving them on the plant much longer than usual. When mature, cucumbers will turn yellow, orange or even brown, beans will turn beige or mottled and summer squash … well, just about any color is possible.
So you have a mature fleshy fruit in front of you. How do harvest the seeds? Simply cut the fruit open and extract the seeds with your fingers, a spoon, or tweezers, then wash off all traces of flesh. Finally, dry them in the sun for a few days before storing them.
Store or Sow Immediately?
Most gardeners sow their seeds in spring, yet most seeds ripen in the fall, hence the need for storing the seeds you harvested over the winter. However, you can also sow the seeds of most hardy plants (perennials, biennials, shrubs, trees, etc.) outdoors as soon as you harvest them, with no special drying or preparation. The seeds of most of these plants need a long period of cold stratification (they have to be kept in moist, cold conditions) anyway before they can germinate and they will get that naturally if you sow them outdoors in the fall. The alternative is to sow them indoors in containers, then to put the containers in the refrigerator for 2 to 3 months before bringing them back into warmer conditions to stimulate germination.
Although you will normally be storing seeds of annuals and vegetables indoors over the winter, there are a few varieties, such as spinach, larkspurs, sweet peas, and snapdragons, that are very tolerant of cold winters. If you sow them in the fall where they are to grow, they’ll germinate all on their own come spring.
Then there is the case of so-called recalcitrant seeds. These are seeds that don’t germinate well if you let them dry out. In this case (and the group includes seeds of several popular perennials, like Cimicifuga, Trillium and Hepatica), simply sow them as soon as the seeds are mature.
It’s best to store seeds cool and dry, in paper envelopes if possible, because paper absorbs any excess moisture (moisture is an anathema to stored seeds). Alternatively, use glassine envelopes, recycled pill bottles or even Mason jars for large seeds. Plastic bags are not always the best for seed storage, as fine seeds often stick to their surface, making sowing difficult.
Room temperature is acceptable for short-term storage (over the winter), but any seed you intend to store for several years is best kept cooler, in a refrigerator, for example. And it’s always wise to write the plant’s name or description and the date of harvest on the envelope. This will help you avoid any confusion come spring.
Should You Harvest Seeds of Hybrid Plants?
If you are a follower of organic gardening, you’ve probably already been warned about the importance of not collecting the seeds of F1 hybrids … but is it really true?
First, you have to understand that F1 hybrids contain, in their genetics, a mixture of genes from two parents. So when you sow the seeds of the F2 (second) generation, the various traits of these ancestors will often come out. If you harvest the seeds of an F1 hybrid maize (corn) with bicolored kernels, for example, you may get plants that bear ears of white, yellow or bicolor kernels! This maize is therefore said to be “not true to type.” If your goal when you buy seed for the first time is to harvest seeds to replant every year, it would be best to stick to non-hybrid varieties (heritage vegetables, for example), because they give essentially identical plants to the parent plant year after year. However, if you like surprises, it can be fascinating to sow the seeds of a hybrid plant: you often get some really interesting results!
If you’re more interested in performance in the garden than harvesting true-to-type seeds, F1 hybrids may be a very good choice, as they often display “hybrid vigor” (heterosis), growing more strongly and producing more abundantly than non-hybrid plants. You’ll just have to buy fresh seed each time you run out.
Separate Beds for “Promiscuous” Plants
Another detail to remember is that, in order to preserve the purity of a seed line, you shouldn’t sow related varieties in close proximity. If you harvest the seeds of your favorite non-hybrid red bell pepper, but grew it near an orange or purple bell pepper, or even a hot pepper, it is likely that bees or other pollinators will have done their duty and carried pollen from one plant to another. As a result, seeds from your plant are likely to be hybrids and thus will not be identical to their parent.
How far apart these plants need to be in order to prevent accidental cross-pollination depends on the species (you’ll find a list here), but for the home gardener, it essentially means that, if you want to maintain the integrity of a seed line, you can only grow one variety of a given plant per garden, period.
For Veggies that Don’t Bloom
Obviously, to produce seeds, a plant has to flower first. But some plants, mostly vegetables, never seem to flower. Why is that?
The reason is that we harvest most leafy and root vegetables (radishes and lettuce are good examples) before they are fully mature. To obtain seeds from these plants, you have to let at least one plant “go to seed,” that is, develop a flower stalk, bloom, and then produce mature seeds.
That’s easy enough to do with radishes and lettuce, which are true annuals: they’ll produce seed the same summer. However most leafy and root vegetables, like cabbage and many of its various leafy relatives, plus rutabagas, carrots, parsnips, beets, onions, Swiss chard, leeks, etc., are actually biennials. They will normally only bloom if you leave them in the garden all winter. When spring comes, they’ll soon send up not only leaves like the first year, but a flower stalk as well. And the flowers will soon turn into harvestable seeds. Problem solved!
However, for you to be able to harvest their seed, biennial vegetables must also be hardy enough to overwinter in your area. In my zone 3 climate, for example, carrots, leeks, and parsnips are hardy enough, but the others will only survive if very well mulched. Even zone 5 is iffy when it comes to the hardiness of most biennial vegetables.
There you go: the basics involved in harvesting your own seed. It’s easy, it’s fun … and you’ll save a ton of money. What are you waiting for?