Q: I have too many weeds to mention, but I want to know what they are. What are some good weed ID resources? —T.G. Northampton
A: Welcome to weed season, T.G! They sure are happy now, aren’t they, after our wet spring and now warm weather?
Depending on what you regard as a weed, you may actually have a few beneficial weeds in your garden space. I know that sounds like an oxymoron, but here is what I mean. Left unchecked, weeds with their keen survival skills and overly fertile nature are the bane of gardeners everywhere, it is true. However, I invite you to consider a few that, under controlled circumstances, can be beneficial. Recognize that we often scowl at the caterpillar but later smile at the butterfly.
One type of weed I have growing abundantly in my backyard is jewelweed (Impatiens capensis). This time of year it seems to grow a foot a day. I have left a whole swath of it back there, though, because last summer when I looked out my back window, I saw a hummingbird happily flitting from plant to plant, enjoying the sweetness within each flower. They do self-seed, but the plants are shallow rooted and easily come out of the soil with barely a tug. What an easy, inexpensive pollinator plant!
Common milkweed is another plant that can be viewed as an annoyance or a benefit. While it spreads prolifically through underground rhizomes, it is a host plant for monarch butterflies. Before clearing my community garden plot this year, I seemed to have a field of milkweed. Trying to make both my vegetables and our local pollinators happy, I have decided to sequester it to a middle circle in my plot.
Weeds such as dandelion and Queen Anne’s Lace can be used to break up hardpan soil that has been compacted during a remodeling project. Their deep roots will help open up the soil, blazing an underground pathway to water and nutrients that desired plants can also use. Clover is a weed that hosts nitrogen-fixing bacteria in the soil, making that element more readily available to other plants. Bees also like it.
Speaking of bees, wildflowers that some people consider weeds have importance to our pollinator friends. Queen Anne’s Lace, for example, is a host plant for swallowtail butterflies, offering a safe haven for their caterpillar young. It is good to know your beneficial caterpillars, too. A few other wildflowers beneficial to pollinators are common mullein, evening primrose and daisy fleabane. That said, feel free to pull out the ragweed, garlic mustard and crabgrass!
Regarding weed identification resources, here are a few helpful ones:
■University of Massachusetts Weed Herbarium
extension.umass.edu/landscape/weed-herbarium
■University of Minnesota Extension
apps.extension.umn.edu/garden/diagnose/weed
■Rutgers University
Good question, T.G. Thanks for asking a local Master Gardener.
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