My friend Bill likes to say that, for both people and plants, “Volunteers are happiest.” Volunteer plants (aka self-sowers/reseeders/self-seeders) grow from seed that was deposited by critters or wind or that simply dropped to the earth from previous years’ crops. If a seedling finds purchase, it means it found its spot favorable in terms of soil fertility, soil type, drainage, sun exposure, etc.
I have dozens of volunteer tomato plants in my vegetable and cut flower plot in the community garden this year. The volunteers popped up both conveniently in corners and inconveniently in the middle of paths. I decided to keep them all but just prune back those stems that were aggressively competing with my planted crops for space. I didn’t bother to stake my volunteer tomatoes or water or fertilize them, as I wanted to see how the fruit tasted when the plants were truly left to their own devices.
If I’d decided to cull out the volunteer plants, as many of my community garden neighbors do, I’d be doing what’s called “roguing.” This year I resisted the urge to rogue, preferring to wait and watch like a good citizen scientist, even though I delight in the sound of “Honey, I’m off to do some roguing.”
Most tomatoes are hybrids, which are crosses between two promising parents made by nature or more commonly, by human (plant breeder) intervention. When hybrids reseed, the new seedling plants may not “come true,”—i.e., they may not have the characteristics of both of their parents, the blend of which made the hybrid so marketable in the first place.
In my garden, the volunteer tomatoes have been by and large tasty (good flavor being the legacy of one parent more than the other), but the fruits have been smaller than you would normally get. So the volunteers haven’t expressed the larger size gene, but they’ve still expressed the tasty gene. (By the way, it wouldn’t behoove me to save the seed from hybrid volunteers, because successive generations are going to be increasingly unreliable and unpredictable in their characteristics. Mendel was all over that.)
So collecting seeds from hybrid volunteers is a dicey proposition. However, unlike hybrids like the fantastic orange Sungold cherry tomatoes that I grow every year, heirloom tomatoes like the wonderful Yellow Mortgage Lifter do come true from seed, which means that you can save seed and expect the new generation of seedlings to have predictable traits.
Besides tomatoes, other vegetables that readily self-seed/volunteer include lettuce, winter squash, pumpkins, and various greens. I keep these volunteers if a) I have the space to run a fun experiment that may or may not be tasty in outcome and b) if I think their chosen locale is going to meet their needs (e.g., for space) all the way to maturity. My friend Jamie’s reseeding butternut squash was incredibly tasty, but another friend’s volunteer butternut was nasty. It’s a genetic crapshoot, and butternut squash vines take up a lot of room (unless you train it up a vertical support system), so your willingness to experiment may depend on how much garden space you can part with.
Reseeding/volunteering annual flowers can be something that garden designers like Liz Elkin of Bloom Landscape Design and Fine Gardening rely on to meaningfully fill space each year. She likes tall verbena with its lavender-purple flowers and counts on its mass reseeding. (On one of the Garden Conservancy Open Days tours, I saw a 25-by-30-foot garden, surrounded by hardscape, that was simply reseeded tall verbena, a sea of purple borne aloft study three-foot stems.) Elkin also counts on California poppies, with their cheerful orange flowers on stems above feathery foliage, to freely volunteer/self-sow as well.
In the right spot, annual plants like perilla, a plant grown for its beautiful coleus-like purple foliage, can reseed in masses with no cost to you. “Perilla can be a little crazy and try to take over,” Elkin says, “but it’s easy to pull out in the spring. I just leave drifts of it where I want it.” She also finds that sunflowers volunteer in gardens readily and are almost always worth embracing. However, if you don’t want no stinkin’ sunflowers—or any other readily self-seeding annuals—simply deadhead seedheads before seed matures and disperses. When you deadhead in this manner, you also save energy for the plant to keep on blooming this year rather than spend its reserves on seed production. That’s why you’ll see me in the early a.m. hours out deadheading petunias in my flower pots. My neighbors think I’m crazy.
So far we’ve been addressing herbaceous (nonwoody) plants. I asked Liz Elkin how she decides which woody volunteers to keep in her clients’ gardens. She says, “I will remove it if it’s going to get scraggly or get too big for the space and range all over and not be attractive. I base the decision on the volunteer tree or shrub’s chosen location and whether it’s a valuable plant or not. For example, a lot of times I’ll find volunteer baby cedars in garden beds. If they’re in the back of a bed with adequate space and an evergreen would look good there, they stay. But if they’re in the front or middle of the bed or don’t have enough space or don’t look right, I pull them.”
Elkin encounters maple tree seedlings (like sugar maple, red maple, boxelder, and Norway maple) more than any other woody volunteer. She mostly doesn’t allow them to establish in gardens. “Maples have extensive root systems, very shallow and efficient, so they’re not good neighbors in an ornamental garden,” she says. “They outcompete everything around them. If I want to plant a maple, I give it its own area and don’t expect to plant gardens underneath it.” This durability can be a real asset. Elkin once let a volunteer maple tree in a chicken yard stay, and now even after the chickens have ripped up the whole area, the tree is still standing and providing essential shade for those scratching poultry.
Another prolific woody reseeder is rose of Sharon. Elkin says, “It’s the best and the worst at the same time because it drops so much seed. It can give you entire beds of rose of Sharon seedlings, but those can make for a nice hedge or you can give the seedlings away.” But again, best not to try to plant ground covers or other herbaceous plants directly underneath.
Elkin has observed that woody specimen plants—cultivars that have been bred and named before coming into the nursery trade—don’t reseed much. This is often because they are bred to be sterile, for many reasons, like eliminating “messy” fruit or preventing invasions into native woodlands. But sterile is no fun; sometimes you want to see jaunty little volunteers everywhere, doing their thing.