Controlling weedy native plants can consume an inordinate amount of time and resources. It can match the effort needed to deal with some of the worst invasive species. However, not all native species commonly labeled as weeds are equally problematic; and some species can become welcome additions to the garden or managed landscape. They can even help in the fight against more problematic species.
What makes a Weed?
Simply put, a weed is a plant out of place. Said another way, “A rose in the cornfield is a weed.” In short, whether plants are—or are not weeds—is largely subjective. Some weeds are undesirable specifically because they are not native to the continent, region, or locality in which they are growing. But this article is not aimed at discussing those species. Instead, the focus here is species native to the eastern United States that frequently get labeled as weeds.
Native plants that often get called weeds generally have one or more of the following characteristics. They can be plants that:
- are aggressively rhizomatous (forming diversity suppressive monocultures)
- produce seed prolifically
- are difficult to eradicate once established
- are early to green up and/or late to senesce
- are coarse in appearance and/or messy looking
- have small, sparse, or not particularly showy flowers
- tolerate poor conditions or a wide range of conditions
Where Do Native Weeds Come From?
In an ecologically balanced system, native weeds rarely become problematic and are kept in check by the natural forces and systems which shaped the biological communities that existed here prior to widescale human-caused disruption of ecological function. After this disruption, certain plants have become more widespread and prevalent than they likely once had been. These include short-lived species adapted to germinate and grow quickly to cover bare soil after natural disturbance caused by things like fire, floods, and game movement; aggressive clonal species adapted to being managed by browsing/grazing, fire or scouring; and species adapted to growing in difficult conditions like dry shade, floodplains and saltmarshes. As humans have changed the landscape and natural systems through soil disturbance, habitat clearing, road salting, and herbivore predator eradication, we’ve helped to create a landscape more suitable for aggressive generalist species—many of which can be seen as weedy.
Beneficial Weedy Characteristics
Viewed through a conventional gardener’s or land manager’s perspective, these characteristics seem to describe species that are largely undesirable. However, with a change of perspective, some plants that fall into these categories can become allies in the garden or managed landscape. Plants in the above categories could also be said to fit into the following desirable categories of plants because they:
- can help to suppress less-desirable species
- colonize poor, compacted, or disturbed soils and help to remediate them for more desirable species
- act as green mulch or groundcover for bare or disturbed soils
- are long-blooming species
- function as a host plant or nectar/pollen rich plant for pollinators
- tolerate poor conditions or a wide range of conditions
- can be resistant to herbivory by deer and other mammalian pests
Any of these characteristics alone would make for a useful plant in the garden or managed landscape, and some “weedy species” have more than one of the above characteristics, making them surprisingly useful. For many of these weedier native species, the key to begin thinking of them as allies rather than enemies is to understand the characteristics that make them either useful or problematic.
How to Work with Weeds
By gaining a clear understanding of the benefits, drawbacks, life cycles, and habits of these so-called weedy species, a gardener or landscape manager can create a targeted maintenance plan that incorporates them. This approach may be preferable to simply removing them wholesale in a misguided attempt to remove all “weeds,” which might potentially be a waste of time and resources.
One of the biggest problems with weedy species in the garden is that they compete for space and resources with more desirable plants. This is particularly the case with plants that spread aggressively through seeds or rhizomes/stolons. However, not all aggressive spreaders share the same traits. While some may be overly competitive, others may be manageable and even desirable, because they can potentially provide a green mulch around more desirable species, and they can help to suppress or outcompete less-desirable species.
Euphorbia maculata (Spotted Spurge) is the archetypal example. This native annual is often maligned for its tendency to seed around freely and occur as a weed between pavers. But in the right situation, it can act as an annual green mulch, helping to simultaneously conserve soil moisture; suppress less desirable weed species seedlings; break up soil with taproots; and provide a dynamic, fine-textured groundcover that is likely to be outcompeted by longer living and more desirable species in time. The way to work in conjunction with this species is to understand its role as a low-growing annual, take advantage of its many beneficial characteristics, and avoid wasting time weeding something unlikely to last longer than a year.
Another common beneficial weedy species in our region is Eupatorium serotinum (Late Boneset). Tall, coarse, and a prolific and aggressive seeder, this plant sounds like something to avoid. Yet it is one of our latest blooming native species, with a large and relatively showy white inflorescence that is highly utilized for its nectar by migrating monarchs and other desirable pollinator species. As a short-lived perennial, it is unlikely to last beyond a few years, and its seedlings can help fill the gaps that less desirable species might overtake. In addition, in a landscape of healthy and dense perennial growth, its seedlings are likely to get out-competed over time. Moreover, if timed cutting is an option, this plant can be cut back twice each season to curtail its coarse appearance and weediness. A mid-June cutback to a foot or smaller ensures a shorter, neater plant and denser flowering. A second cutback post-flowering prevents plants from going to seed too prolifically. Working with this plant requires an understanding of how and when to manage its growth to take advantage of its desirable characteristics and curtail those that are less desirable.
Sometimes, it may be somewhat controversial to label a specific species as a weed. This is particularly the case with Asclepias syriaca (Common Milkweed). It has weedy features in that it is tall, has broad/coarse leaves, is aggressively rhizomatous in gardens and meadows, and is a long-lived perennial. However, it is also the best host plant for Monarch butterflies (a charismatic species partially imperiled by lack of habitat and its host species A. syriaca), it has large clusters of fragrant flowers, and it is a prized wild edible. Clearly this is a plant that belongs in our landscapes, but it needs to be used appropriately to be most effective.
This plant should be used in places where you’re not concerned about it spreading into—and out-competing—adjacent species. While Milkweed’s growth habit does not make it a great choice for a cottage garden or perennial border, it can work well as a property edge plant; in a single-species bed; as a component of a taller rough-and-tumble planting with similarly aggressive native species like Panicum virgatum (Switchgrass), Monarda fistulosa (Wild Bergamot), and Symphyotrichum novae-angliae (New England Aster); or even in a container or raised bed. With the precipitous decline in Monarch populations, encouraging the growth of Common Milkweed is of paramount importance—but that need not come at the expense of having a neat and diverse garden or meadow. By understanding and leaning into the aggressive, clonal growth habit of this plant, it can successfully be used as part of our landscapes while still leaving space for more refined plantings.
Achillea millefolium (Yarrow) is another species that is called a weed by some but is seen as desirable by others. It is tough and often found as a component of lawns in poor soils. As a fast-germinating plant with dense basal leaves, it can shade out more desirable species in early meadow development. However, its dense basal leaves are attractive, finely dissected, and highly medicinal. It is also a long-blooming species used by a wide range of pollinators, and it can be mowed as low as most lawns and still thrive. In addition, even without flowering, this plant provides host plant value for Painted Lady butterflies and several species of moths (the unsung heroes of the pollinator world). In doing so, it brings some badly needed diversity to the American lawn.
Finally, when Yarrow is interplanted with other containerized plant material (rather than grown from seed), its basal leaves are low and dense, providing green mulch benefits like the previously discussed Euphorbia maculata (Spotted Spurge). In this case, understanding the aggressive nature of this plant and how to leverage it (either by mowing or not growing it from seed with other species) accesses its benefits and avoids its drawbacks. It is worth noting that Achillea millefolium has a circumboreal distribution (multiple varietals are found native to Europe, Asia, and North America). Therefore, with this species understanding the provenance of the plant you’re using can mean the different between planting a native genotype and planting a genotype from around the globe.
While not all weedy native species have characteristics that make them adaptable allies in landscape management, it is worth understanding which species can function in this manner. They can greatly improve landscape health and assure a more efficient allocation of time and effort.