How Do Gardeners Make the Most of Self-Seeding Perennial and Annual Plants?

There is a fine line between plants having invasive tendencies and plants being glorious self-seeders. I see most self-seeders as beneficial. I like tightly packed plantings that grow on the wild side, and I love not having to dig in all my plants by hand. But self-seeders can be a nuisance to gardeners who crave a more controlled look.

I started thinking about this while admiring winter evidence of one perennial self-sower, Sweet Autumn Clematis. In January it looks like dried vines topped with swirls of spun sugar… puffs of white filament to help carry the Clematis seeds on the wind. 

Most of the seeds of this perennial are now gone, having left behind only their once-cradling brown pods that are similar in appearance to star anise. This perennial which would not take hold when I tried to grow it from a plant-start began to grow prolifically after a seed or two hopped my neighbor’s fence and entered my yard. I welcomed this vining beauty which continues to self-sow and expand into mini plants around my yard. It is one of my fastest-multiplying perennial plants, doing all the work on its own. Now that is what makes for a self-seeder, or what we might more aptly call a self-sower. Self-sufficiency on the part of the plant is what permits us to enjoy new plants in the future.

Perennial Versus Self-Seeding Perennial

Hearing the term “perennial”, you would think, “well, that is a plant that returns year after year anyway.” And yes, Sweet Autumn Clematis like virtually any other perennial comes up by its roots in a yearly cycle of growth, dormancy or die-back, and new growth. But a self-seeding perennial not only grows back from the same roots that drew up nourishment in summer, but it also casts seeds to form new plants with new roots in new locations.

There are also self-seeding annuals which are not slated to come back but do, after they ensure their self-fertile seeds hit the ground and start their work of taking hold before winter arrives. For me, Portulaca is one of these, growing only as an annual in my area. Its roots do not make it through winter. And yet, with the right mix of conditions, it can be left to go to seed and self-sow to form new plants that appear when summer returns.

Erodium grows as a perennial in my area. Knowing that little Erodium plants pop up all over my garden thanks to generous mother plants, I looked it up. Would you believe that one variety flings its seeds quite a distance from the mother plant, and then with a little help from changes in humidity, the seeds drill (yes, drill) themselves into the ground? In their plant DNA is the knowledge that this flinging and drilling are vital to moving the variety forward… vital to persisting and propagating. The human hand could do no better at getting the planting job done.

Many Alpine plants such as perennial Edelweiss are self-sowers. They are programmed to multiply on their own, at high altitudes and in unfavorable soils, without the help of birds or cross-pollinator plants. 

“Magically appearing” new plants, lush growth, and a naturally random look to the garden… I love all this. I love self-seeding plants.

Different Perceptions about Self-Seeding Perennial and Annual Plants

So back to my self-seeding perennial Clematis: I shared my happy story about my annual bounty of new, baby plants with a friend. My friend met my joy with frustration and said, “Oh, I had it once too and got rid of it because it was dropping seeds everywhere and taking over.” One person’s gift can be another’s problem. 

Not everyone loves perennial and annual plants that self-seed. Some fear they will become too aggressive and prevent by-hand plantings from having adequate space to grow. And all gardeners, whether they love self-sowers or not, must heed the rules of their states and provinces when it comes to invasive plants that are not allowed to be sold in, bought in, or shipped to particular areas. But with personal preferences and local rules acknowledged, there are some different approaches that can be taken with self-seeding plants.

What to Do

First, it helps to reference a good list of much-loved perennial plants, both self-seeders and others. I find it beneficial to use a list that includes basics on pruning and tending, as trimming back flowers is what keeps seeds from forming. Knowing what is generally considered the best time to snip and trim, more research can be done to determine which of these perennial plants are self-seeders. The self-seeders can be allowed to drop their seeds if that is desired, or gardeners can jump the schedule and remove flowerheads before any sowing begins. Specifically, you can do the following:

1. After they flower, let plants go to seed and maintain empty seed pods for winter interest. Tidy up plants in spring, not fall. Just check good perennial guidelines for a sense of when most gardeners prune and trim so that you leave the seeds on long enough but not so long as to prevent new buds from forming.
2. Nurture self-propagated seedlings which emerge in spring and summer. Try to let them stay in place for the first season so that they grow strong.
3. Once new plants are well established, transplant or gift them if they become too dense in any one area or are poorly positioned in the garden.
4. If too much of a good thing becomes TOO MUCH, deadhead flowers on self-seeders the moment they start to fade. Do not permit them to go to seed. Control with pruning and cutting back rather than using chemical means of halting growth.

With Step 4 above being key, although there is only a fine line between invasive and gloriously self-seeding perennial and annual plants, it really seems the gardener has lots of control. Deadhead quickly to prevent self-sowing. Or, conversely, you can maintain seed heads and let the seeds fall where they may if you want to go for a more abundant and natural garden look. 

Gardeners are not meant to control everything, but taking smart steps makes a difference in how plants work for us (rather than create work for us). A few such steps allow us to enjoy what self-seeding perennial and annual plants offer, while not letting them completely run the show.