Living Fast, Dying Young: The Case For Native Annuals
I'm going to point out something obvious: yards in my area (and probably yours) have problems with non-native weeds.
They take all forms. Insidious tap-rooted types like creeping bellflower; ephemerals like pennycress that leave their chattering ligno-cellulosic skeletons haunting our perennials; maddening advantageous sorts (like dandelion and annual chickweed) that literally appear overnight in our freshly-tilled beds; and the most insidious of all, rhizomatous grasses that escape the lawn in search of less crowded spaces. And then there are noxious weeds (weeds level: expert) whose impacts reach far beyond the humble garden. Regardless of form, the gardener's struggle is real.
I know, you're reaching for the Roundup. Stick with me...
The thing is, we only have ourselves to blame. Weeds the world over have one thing in common: they love disturbance. Gardening, fundamentally, is disturbance. Our digging, back-and-forth trampling, weeding (irony!), and tilling replicate (in miniature) the fires, landslides, stampedes, volcanoes, and floods that have shaped species assemblages on a landscape scale since plants first colonized dry ground.
Weeds are opportunistic, rapidly colonizing earth laid bare by some calamity or other. Most are annuals (emphatic stomp for those taking notes), meaning they plunge all their resources into one season's epic quest to produce offspring. As the growing season draws to a close, the literal seeds for a new generation are poised to resume habitation of a formerly inhospitable site. This life strategy serves a purpose far greater than each enterprising little weed sprout; it prepares the site for slower growing, longer lived species who will build upon what the weeds have started. Weeds add nutrients, break up compacted soil, and provide shade for perennial seedlings. Ecologists even have a special name for weeds: ruderal species (which comes from the Latin word for rubble).
This life strategy isn't without its drawbacks. In time, the weeds will be unable to compete with their longer lived neighbors, whose more efficient use of resources and resilience to moderate disturbances will give them a substantial edge. Weeds are a sort of sacrificial wave who soften the beach heads for those who follow. Think of how crucial that is.
Let's zoom back down to a garden scale. As we putter around our yards, we are creating a fundamentally altered ecosystem with excessive amounts of disturbance. The weeds-to-short lived perennial-to-long lived perennial progression simply isn't going to happen on its own (this is probably true for a lot of our open spaces too, but that's another can of worms). Weeds (and the services they provide) are not only inevitable, they are necessary.
Enter native annuals. We have some delightful native annuals here in western Montana, and guess what: they're weeds! Like the dandelion and the pennycress, our native annuals rapidly fill in bare ground and do what all weeds do best: produce more copies of themselves in a very short time. Even self-proclaimed "brown thumbs" or plant killers of ill repute can reliably make the perfect habitat for a native annual. Simply remove an existing plant (an unwanted weed, let's say. Totally hypothetical), and there you go. As far as our native annuals are concerned, you are a top-tier terraformer.
Too often gardens are planned with neat widely spaced rows of perennials and great expanses of bare earth in between that, frankly, are just asking for weeds. Nature abhors a vacuum, as it were. Gaps are not something you see on the landscape for very long.
So imagine that you beat nature to the punch and seed native annuals in the gaps between your perennial plantings. This would do two things: it would make life a little easier for your native perennials, as these evolutionary-parallels aren't out for their lunch (so to speak) while still providing essential services (breaking up compaction, adding nutrients, shading); and these native weeds would effectively remove that tantalizing blank slate that encourages non-native weeds in the first place. I've started to suspect that we spend a lot of time and energy on perennial plantings when it's sort of putting the cart before the horse, ecologically speaking.
I've been practicing this in my own little yard with some (fairly long-lived, at this point) patches of clarkia and Rocky Mountain beeplant (I have owl clover and collomia going now too, but they are new to my experimental space). I seeded each species once, and they have persisted where perennials haven't managed to establish. The clarkia in particular is very effective at blocking less-desired species from otherwise uncolonized space.
A few years back I had a landscaper complain that clarkia would be nice, but he wouldn't be planting it anymore as it was too weedy. They get everywhere, I was told. In between all the plantings. And they persist. Then he complained about having to weed all the time. Not clarkias, just...weeds.
I wasn't sure what to say at the time (that's just how I am). But now I think: if you disturb the ground, weeds will appear. It's an open invitation. Wouldn't you prefer that they were clarkias?
Bellflower image credit: D. Gordon E. Robertson - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=9600651