Our goal is to create a sustainable garden, so our seed crop needs to be as extensive as our food crop. Seed harvesting is a simple process, though growing plants for seed requires a different approach. While many plants produce adequate seeds without extra effort, many require you to designate a portion of your garden as a seed garden, specifically for plants needing the entire season and biennials. This allows you to leave these plants alone, while still reusing much of your growing space for second crops. Bedding plants like asparagus, mint, and strawberries will do fine on their own. Woody plants like blueberries and grapes are best propagated via cuttings, which is another article entirely and to be covered another time.
To keep from having too long of a read, I’ll split this topic over two posts, organized as non-seed garden versus seed garden.
Part One: Non-seed garden plants
Several plants, particularly beans, do not need to be part of the seed garden. Because they generate enough output as is. Plants which we grow and which produce sufficient seed on their own are: tomatoes, tomatillos, cucumbers, beans of all kind, melons, squash/gourds, peppers, eggplant, potatoes, and a number of herbs. Although lettuce and spinach will bolt easily and corn produces plenty of seed, I plan to reuse these spaces during the season, so I include them in the seed garden.
How much seed is enough? Plan for 80% germination rates, i.e. one in five won’t sprout. So I would harvest five to get four plants. Normally, I get more than enough seed and this is not a concern. In fact, I give seed away. If you are a vendor at Farmers’ Markets, consider selling your excess seeds. A simple label printed from your computer and placed on a white or manila envelope is sufficient packaging.
Always try to take seeds from the two or three best fruits to preserve seed disparity. For the most part, seeds should be collected from what we consider to be overripe fruits and vegetables, including those on the verge of rotting. Remember, the plant is not producing food for us; it is producing seed for itself. The stage at which we consider something to be ripe is not its final stage. To get the best seed, we need to let the plant complete its growth cycle. This may involve letting the plant drop the fruit and picking the seed from what to us is a mess or a disgustingly gloppy tomato, etc.
Potatoes are the easiest of all, and to which the above paragraph doesn’t apply. When you harvest, you will have spuds of all sizes (and usually shapes). There will be tiny little nuggets smaller than a marble and others large enough for two or three people to share. You will be looking for the golf ball sized ones to use as seed potatoes next year. Don’t wash them. Gently wipe them clean with a soft rag. The thin coating of soil, which remains, is protective. Put them in a mesh bag, or plastic bag with several holes punched into it, and store them somewhere cold and dark. I keep them in the vegetable bin of our old refrigerator in the basement.
Horseradish is similar in that you start new plants from root cuttings. I grow mine in large, clay pots to prevent it from spreading and taking over. I have two pots started in alternate years to allow two years of growth before harvesting. Take your smaller roots or a root end and place it in water until it sprouts. When the leaves are two to three inches tall, pot it and keep it indoors until spring when you transfer it to the big pot. Like potatoes, you can refrigerate these rootlets for a while, although they readily sprout during storage.
While we primarily propagate asparagus through root expansion, the plant does produce seed. The time from starting asparagus from seed to having a stand ready for harvesting is longer by as much as three years over planting bare roots or live plants. Asparagus seedpods look like small, red berries as they develop. Allow them to dry as much as possible on the stalks. Clip and invert in a paper bag to finish drying inside. When ready, the pods will split open and drop seeds into the bag. Usually. You may need to break them open to remove the seed.
Allow some celery flower stalks to mature into seed. Let the head dry and invert them in a paper bag to catch the seed. Commercially sold celery seed may have a germination rate of only 55%. This means you’ll want twice as much of it as of other plants. Conversely, celery seed is quite potent in flavor so you don’t need much in culinary uses.
Beans, fresh and dried, are a staple in our diet. These plants are so prodigious we generate seed almost by accident. From experience you will learn, as did I, that bigger does not mean better when it comes to beans eaten fresh. The fatter a green pole bean or bush wax bean gets, the chewier it gets. As rich in dietary fiber as beans are, they become more fibrous as they mature toward seed. This means those pods with nicely rounded beans bulging within are the ones you don’t want to pick. When they reach that point, and it seems to happen overnight, leave them for seed. Allow the pod to completely dry out before harvesting. If a period of wet weather is coming, pick pods that are almost dry as extended rainy periods can soften them to where the seeds drop out to the ground or sprout in the pod.
Harvest peas in the same manner as beans. Although I will follow my spring crop with a fall crop, so I leave the two strongest plants in place with a number of pods I chose to leave to mature into seed.
The below seeds are dried on pieces of screen after harvesting. You can build frames to hold them, but make it easy to remove the piece of screen in case it becomes clogged with residue and needs to be tossed. All seeds need to be shuffled daily while drying to prevent sticking or clumping. Remember to label your screens; you will have several types drying at once.
Tomatoes and tomatillos require a bit of work, though not too much. The gooey, pulpy material around the seeds is a germination inhibitor. This adaptation in the fruit prevents the seeds from sprouting until they have come into contact with soil and are separated from the gel. Simply washing it away from the seeds is the second best method of harvesting these seeds. It is messier and less successful than the preferred technique of fermentation.
Place the seeds with their surrounding goo into a sealed container and keep it in a cool, dark spot. For me, that’s a shelf in the basement. Stir up the mess a few times a day. After forty-eight to seventy-two hours, but never longer, add a little water and slowly poor off the gel. Most of the seeds should sink, although some won’t. Repeat the process until you’ve sloughed off as much of the goo as possible. Spread the seeds on a piece of screen to dry as described above.
Cucumber seeds are harvested via fermentation also. The only difference in the process is that you add a small amount of water to the container along with the seeds and gel at the start. Once you’ve scooped the seeds, of course, you can still eat the rest of the cucumber or pickle it. You cannot harvest seed after pickling them.
Similarly, with summer and winter squash, which includes pumpkins, you want to harvest the seed before cooking. For summer squash, like zucchini and yellow crookneck, it’s normal to cook whole. However, for winter squash, particularly butternut and pumpkin, it can be easier to remove seeds after baking them whole. I know I always sliced and removed the seeds before cooking at first. I learned about cooking them whole as I grew as a home, self-taught chef. Squash seeds simply need to be cleaned and dried. You can still clean, dry, and roast pumpkin seeds for eating after baking the gourd first.
Melon seeds need a good rinsing to remove the sugars from the fruits. This is to prevent two things. One, wild yeasts or fungi potentially may find and rot the seeds. Two, mostly you are trying to keep fruit flies at bay. Those little buggers don’t need much to establish themselves and are a pain to eradicate. You don’t want to find yourself in the position of holding your breath suddenly because you’ve stepped into a cloud of fruit flies. As mentioned above, the best seeds will come from overripe melons, i.e. at the end of their growth cycle. If one squishes in your hand when you go to pick it, that’s your seed melon.
We keep a perennial herb bed in which I’ve included parsley despite it’s a biennial. Like my horseradish, I have it in two places planted in alternate years. One is for the leaves and the other is for seed. Fortunately, I have the extra space where we’ve placed the herbs. Oregano, mint, and catnip (for the girls) will do fine on their own and will spread like wildfire from a well-established bed. You may not need to harvest seed for use, but rather to keep them under control. Sage, chives, and other perennials will flower and produce seed, although I generally remove the stalks or heads to promote bushier growth.
Basil and cilantro I grow in the main area because I will get seed from same plant I am using for leaves. Simply let a few flower stalks remain and mature until they are dry on the plant. Both are very eager to bolt and it’s usually more challenging to keep them under control than to encourage flowering. The same goes for dill, which I grow in a clump to get enough of the tiny leaves and hide our recycling bin. Dill is as bad as mint about spreading, though. So keep it under control. Clip the dried seed heads and stalks and invert them into a paper bag. If you don’t intend to use the seed heads for pickling or seed, clip them green and add them to the composter.
Be sure to label the bags. I currently have eight different bags in use between herbs and flowers. Reuse your paper bags until they tatter, then recycle them. Keep them in a container or basket, when you take them out for harvesting, to prevent damage from wet grass, mud, etc.
Once collected, store your seeds in sealed envelopes in a lidded container (coffee can, Tupperware) in the refrigerator. Most seeds require a period of chilling to fully mature. This is an adaptation, which prevents seeds from sprouting too early in the spring and which is called cold stratification or, sometimes, vernalization. Not all seeds require cold stratification, such as tomatoes, although it doesn’t hurt them. Just don’t freeze them. I use #1 and #7 coin envelopes, and place them in a coffee can in my basement fridge. Label them for the contents and the year of harvest. I keep a container for each year. When you begin using them for greenhouse and outdoor planting, return the envelope, paper clipped shut, to the container and the refrigerator.
If I didn’t discuss something above, I’ll cover it in part two on seed gardens.