The following excerpt is from Jared Rosenbaum’s forthcoming book Wild Plant Culture (New Society Publishers, November 2022: Pre-order here at a 20 percent discount) and is reprinted with permission from the publisher.
Many people fear weeds. They carry a cultural stigma, and signify failure in the garden or home landscape. With the growing awareness of invasive plant species, this fear has become almost paralyzing for some.
To dispel that fear, it is best to better understand weeds. Here is a simple two-part perspective on weeds:
- Weeds are a symptomatic response to a particular type of disturbance.
- Shift or eliminate the disturbance, and the weeds will not recruit again.
There’s two things here that work in our favor. First, weeds need specific types of disturbance to successfully disperse, germinate and thrive. Most weeds are species of exposed bare soils. They are annuals or biennials that take quick advantage of resources that are not tied in to the cycles of an established plant community. They grow, seed and move on, unless the disturbance is repeated.
Annuals and biennials are primarily a threat to the perennial plants we are nurturing or establishing only when our desired plant community is just a year or two old. For example, a newly seeded meadow on bare soil could be overwhelmed by annual and biennial weeds in its first couple of years unless managed with intermittent mowing designed to keep weeds at the same height as native seedlings.
Most of the commonly known weeds are annuals. These are the species that show up in the carefully bared soils of vegetable gardens and in the disturbed soils we create with machinery in the urban and suburban landscape. They include amaranth, foxtail grass, lamb’s quarters, purslane, galinsoga, smartweed and horseweed.
I’d be remiss not to mention that a large percentage of garden weeds are also good edibles. We disturb some soil on our farm every year (with the ostensible purpose of a vegetable garden) in part because of the fantastic crop this yields of amaranth and lamb’s quarters, both exceptional cooked greens. If we didn’t till the soil in this patch, it would rapidly colonize with asters and goldenrods like the meadow just upslope.
Which leads to the another simple precept about weeds: Most annuals and biennials do not compete effectively with established perennials.
Right near our “vegetable garden” (AKA annual weed patch) is a small planting of tall coneflower (Rudbeckia laciniata) that we maintain for its edible greens. It’s specifically desirable because it commences new basal leaf growth very early in the spring. As a green, it is available well before any garden vegetable greens like spinach or lettuce are ready to harvest. It’s available well before dandelions, even.
Here’s a hypothetical scenario. Let’s say one of the lamb’s quarters seeds from the garden fell across the path and landed in the tall coneflower patch. While the lamb’s quarters are germinating (often late in spring), the tall coneflower has basal leaves almost 2 feet across, and is starting to bolt for the season. Maybe it’s a couple of feet tall already. The lamb’s quarters don’t stand a chance. Even an annual weed that germinates just as tall coneflower begins its growth in March would be hard-pressed to maintain the growth or access the resources that this well-established native perennial can.
Read more: Learn more about foraging lamb’s quarters!
Understanding these two basic precepts about weeds can save us a lot of time and angst as our perennial communities mature. A weed is not a problem sheerly because of its presence, as most of us fear. It is only a problem … when it is a problem.
The species that are problematic are good to know. Not just by name, but by lifestyle.
In understanding their tactics and duration, it is possible to understand the nature of the problem they present, and a good deal about avoiding, outsmarting, or eliminating them.
For example, Japanese stiltgrass is an extremely competitive weed. It is also an annual. It grows in thick swards sprawling over anything shorter in stature and creating great heaps of thatch that only it seems to be able to germinate through. Rodents like to tunnel beneath its thatch and gnaw on native perennials. Woody plants sometimes suffer from insufficient airflow in swards of stiltgrass.
We mow Japanese stiltgrass right around Labor Day (early September), as it is setting seed. Timed right, it will not have the root reserves to flower again and set seed before the frosts of October. Mowing also chops up the thatch that it would otherwise create, freeing plants and seeds below from its inhibitory effects. If stiltgrass is managed in this way, I’ve seen new infestations disappear in as little as one year.