ILLUSTRATION: ELAYNE SEARS
One of the characteristics of a truly sustainable garden is that it produces at least some of its own seed. This is most often done when gardeners select, harvest and store seeds until the proper time for planting the following year. But some self-seeding crops produce seeds so readily that as long as you give them time to flower and mature, and set seed, you will always have free plants growing in your garden. You can simply let the seeds fall where they are, or toss pieces of the seed heads into the corners of your garden, or whichever area you want them in — no harvesting, storing or replanting required. With most self-seeding vegetables, herbs and annual flowers, you’ll just need to learn to recognize the seedlings so you don’t hoe them down. Should seedlings require relocation, you can simply lift and move them — after all, they are sturdy field-grown seedlings.
In addition to getting all the free garden plants you need (and some to share with family and friends), nurturing self-seeders is also a great way to provide a diversity of flowers that supply pollen and nectar for beneficial insects. Self-seeding flowers, herbs and vegetables that show up in early spring include arugula, calendula, chamomile, cilantro, dill, breadseed poppies and brilliant red orach (mountain spinach). Nasturtiums, amaranth, New Zealand spinach, and even basil or zinnias appear later, after the soil has warmed.
Starting a new colony of any of these annuals is usually a simple matter of lopping off armloads of brittle, seedbearing stems in the fall, and dumping them where you want the plants to appear the next season. It’s that easy. Most of the seedlings will appear in the first year after you let seed-bearing plants drop their seeds, with lower numbers popping up in subsequent seasons.
Working with reseeding, or self-sowing, crops saves time and trouble and often gives excellent results, but a few special techniques and precautions are in order. Some plants that self-sow too freely — especially perennials such as garlic chives or horseradish — will cross the line into weediness if not handled with care.
Spring Seeds for Fall Crops
The first group of plants to try as self-sown crops — both because they’re the easiest and they’ll be ready the same year — are those that tend to bolt in late spring. If allowed to bloom and set seed, dill, radishes, arugula, cilantro, broccoli raab, turnips and any kind of mustard will produce ripe seeds in time for fall reseeding in most climates. Lettuce will take a little longer, but often gives good results in Zone 5 or warmer.
One way to encourage self-seeders is to select vigorous plants from a larger planting, and let these plants grow unharvested until they bloom and produce seeds. This will work well enough, but it’s often bothersome to have one lone turnip holding up the renovation of a planting bed. To get around this problem, use a Noah’s ark approach: Set aside a bed or row and transplant pairs of plants being grown for seed into the ark bed. As the weeks pass, weed, water and stake up seed-bearing branches to keep them clean, but don’t pick from the “seed ark” bed.
When seed pods dry and begin to shatter, gather and store some of the seeds as usual for replanting next year (just in case the reseeding effort isn’t successful). Shake and crumble the rest where you want the next crop to grow, and pat the soil to get good contact between soil and seeds. Or, simply lay well-broken seed-bearing branches over a prepared bed and walk over them. This will shatter seed pods and push seeds into the soil at the same time, and the stem pieces will serve as a starter mulch. With fast-sprouting crops such as arugula, a drenching rain or good hand-watering is all it will take to bring on a lovely fall crop.
Many of the seeds that hit the ground will rot or be eaten, but hundreds will survive winter and sprout in spring. Their strength is in their numbers. When you sow a bed of cilantro, for example, you might plant between 25 and 50 seeds. But when nature is in charge, a single plant may shower your garden with a thousand fresh, plump seeds. Cilantro seedlings are easy to dig and move, and they make well-behaved “weeds.”
Managing Annual Self-Seeding Crops
Many annual crops will reseed themselves if you leave them in the garden long enough for the seeds to mature and the fruit to decompose. Annual veggies that frequently reseed and provide volunteer seedlings include winter squash and pumpkins, tomatoes and tomatillos, watermelon, and New Zealand spinach.
There are two issues to consider when managing this band of garden volunteers: disease and location. The two most serious diseases of potato and tomato — early and late blights — can actually be perpetrated by encouraging disease-carrying volunteer plants. Especially if you saw late blight in your garden the previous season, you should seriously consider breaking the disease cycle by digging up and composting potatoes that sprout from the previous year’s patch, along with all volunteer tomatoes and tomatillos that appear early in the season.
However, sometimes in late summer, I do adopt tomato volunteers that have a potato-type leaf, because I know what they are. ‘Brandywine’ is the only potatoleaf tomato variety I’ve grown in the last five years, so any potatoleaf volunteers are highly likely to be ‘Brandywines.’ You also can recruit healthy volunteer tomatillos based on their distinctive leaf shapes. I locate these foster children around the garden as single plants, spaced far from my main ripening crop. Or you can consider moving volunteers to containers and growing them outside of your garden as a disease safety precaution. With late blight, it’s better to be safe than sorry.
If you’re growing open-pollinated (OP) varieties, it can be fun to let volunteer winter squash, pumpkins, gourds and watermelons ramble along the garden’s edge, or scramble over wire fencing. (Remember that seeds from hybrid varieties usually won’t grow “true to type.”) Check the plants weekly for signs of powdery mildew disease, which is a common problem with older open-pollinated varieties. Squash or pumpkin plants that show signs of powdery mildew before the fruits have set should be pulled out, but don’t worry if the white mildew patches appear later on when the fruits are almost ripe. The plants will still bear a good crop. If volunteer winter squash are always a part of your garden’s landscape because so many seeds survive in your compost, you can introduce powdery mildew resistance to your local population by growing OP varieties which are resistant to powdery mildew, such as ‘Honey Nut’ butternut and ‘Cornell’s Bush Delicata.’
Controlling Rampant Self-Seeders
Several useful herbs and greens reseed with such abandon they must be handled as potentially invasive plants. Plants behave differently depending on the climate, but in general, expect the following crops to become obnoxious if not given appropriate discipline: borage, chives, garlic chives, edible docks and sorrels, herb fennel, lemon balm, horseradish and valerian. Here are the house rules:
- Grow only as many plants as you can monitor.
- Don’t allow seeds to be shed in your garden without your permission. This is done by pruning off flowers or immature seed heads, many of which make fine cut flowers.
When experimenting with herbs from around the world, I have learned to be cautious, because one year’s seed can be many years’ weeds. Start with small plantings of nigella, perilla, and seed-producing sorrels and docks to make sure you can keep them under control. Intervene early should a reseeding plant you don’t want start popping up everywhere. Weed ruthlessly until it’s gone, because ill-mannered thug plants have no place in a well-managed garden.
34 Easy Self-Seeders
Herbs: basil, chamomile, cilantro, cutting celery, dill, parsley
Vegetables: amaranth, arugula, beets, broccoli raab, carrots, collards, kale, lettuce, orach, mustards, New Zealand spinach, parsnips, pumpkin, radish, rutabaga, tomatillo, tomato, turnips, winter squash
Flowers: bachelor button, calendula, celosia, cosmos, nasturtiums, poppies, sunflowers, sweet alyssum, viola
Bountiful Biennials Set Seeds in the Spring
If you can get them through winter in good shape (a challenge north of Zone 7), openpollinated varieties of beets, carrots, collards, kale (especially Russian strains), broccoli, parsnips and parsley can be added to your list of self-sown crops. These crops produce their seeds in the second year. Cold frames or low tunnels work surprisingly well at enhancing the winter survival of these plants, or you can try replanting stored beets, carrots or parsnips in late winter, as soon as the soil thaws.
To get prompt, strong flowering and seed production from most biennial vegetables, it’s important to have nearly mature plants that have been exposed to at least six weeks of cold with soil temperatures in the 40-degree-Fahrenheit range. In the spring, warming temperatures and lengthening days trigger overwintered biennials to flower profusely, eventually producing great stalks of flowers for bees and beneficials, followed by thousands of seeds — a single parsley plant may shed the equivalent of 10 packets of seeds. You will see most of these seedlings in the first two seasons after a reseeding. By the third year, it’s time to repeat the drill.
The best time to plant biennial seeds is late summer to early fall, using the seed ark approach described earlier. For example, you might grow pairs of carrots, Russian kale, and parsnips together, and protect the young plants through winter with a low plastic-covered tunnel. By midsummer the following year, you should have enough fresh seeds to save and scatter where you want new seedlings to grow, just in time for fall planting.
- In the fall, toss seed heads wherever you want seeds to germinate. Or, next spring, transplant volunteers to the spots where you want them to grow.
- Be sure not to hoe “weeds” too early in the spring.
- Learn to identify the self-seeder seedlings.