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What is a weed?

In the time I’ve spent as a crew member working with Howard Ecoworks, this is a question that I’ve faced in a number of ways.

New crew members with experience in commercial landscaping have one idea, lovers of the environment have another, and residents watching the rapid growth of their rain gardens have yet another. The dictionary definition comes close, but misses a few important points. According to Merriam Webster, a weed is “a plant that is not valued where it is growing and is usually of vigorous growth, especially one that tends to overgrow or choke out more desirable plants”. Though how we determine which plants to value where they are growing, or which plants are more desirable, tends to vary.

At Ecoworks, you’ll probably never hear an employee refer to a plant as a weed. It’s said that there’s no such thing as a bad plant- just plants that aren’t where they belong. And while most people first think of plants like dandelions and clover, there are likely far worse invaders going unnoticed in your local ecosystem. It’s important to understand the main factor in deciding which plants are valuable where they are growing, and which aren’t: native species versus invasive species. Here, a quick lesson on the different “weeds” I encounter in building and maintaining rain gardens and conservation landscapes.

Plants that just don’t belong-

Nonnative, or invasive, plants (plant species which were introduced to Maryland from another location, which compete for resources with and typically dominant native plants). Marylanders have likely heard of kudzu (Pueraria montana), but may be less familiar with other invasive plants like japanese stiltgrass (Microstegium vimineum) carpetgrass (Arthraxon hispidus), mile-a-minute (Asiatic tearthumb), oriental bittersweet (Celastrus orbiculatus), and garlic mustard (Alliaria petiolata). These plants may go unnoticed, but will quickly take over a garden and choke out native plants, which pollinators prefer.

Plants that aren’t actually bad-

Nonflowering native plants like grasses, phlox, mosses, ferns, or shrubs aren’t weeds! Just because a plant isn’t “pretty” doesn’t mean it’s useless- in fact, native grasses like little bluestem (Schizachyrium scoparium), red fescue (Festuca rubra) , and yellow indiangrass (Sorghastrum nutans) do much more for the environment than nonnative flowers or turf grasses.

Native Plants that aren’t so great-

Though plants like smartweed, poison ivy (Toxicodendron radicans), three-seeded mercury (Acalypha virginica), or dogbane (Apocynum cannabinum) may be native to our area, they are typically removed from gardens due to their aggressive nature. These plants spread quickly (some inflicting pain to humans and our pets), and generally reduce overall biodiversity in green spaces.

“Weeds” that are actually good-

Native plants called weeds actually provide valuable ecosystem services like water and air filtration, and providing shelter or food for wildlife. Milkweed (Asclepias syriaca) and joe pye weed (Eutrochium purpureum) for example, are key host plants for butterflies. I once saw a milkweed in one of our rain gardens fully cut down by a resident who wanted to maintain the garden- the right mindset, but more harmful than helpful!

Again, there is no such thing as a bad plant- just plants that aren’t valuable where they are growing. Familiarizing yourself with common invasive plants could do wonders for enhancing your garden, yard, and ecosystem. It turns out dandelions aren’t so bad after all.

by Georgie Hardesty

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