Get our newsletters

Tips for the Compleat Gardener: Alliaria petiolata


Out in the untamed woodlands that speckle the bigger picture, home to native flora and fauna, birthing place for the wild things, our fading connections to ancestors on the edges of our mutual byways, spring is unfolding.

Dogwoods are lighting up the rainy day, spring phlox and opening lily-of-the-valley are scenting the moist air, birds are singing love songs and bare ground has become green, some hosting innocent-looking invaders of which Alliaria petiolata [al-li-AY-ria pet-i-o-LAY-ta] (which essentially means with similarity to the alliums and having a stalk) is one.

Commonly known as Garlic Mustard (pictured), the 2-foot-tall plant that manages to take advantage of warm and wet spring weather to become tall and blooming before one notices, simultaneously targeting arbuscular mycorrhizal fungi and causing tree saplings failure to thrive. According to Kristina A. Stinson, a plant population biologist, research indicates that the garlic mustard interrupts the delicate system of nourishment between soil organisms and tree roots.

Nourishing soil is teeming with microscopic life that transforms and transports nutrients from environment to plant life; some are relatively evident such as earthworms and ants, and others only visible under a microscope. In a balanced state the environment around the roots of your garden plants is like a little factory with every organism co-operating until a ruthless invader (or poisonous application) sends interfering chemicals to disrupt.

Experiments found that Garlic mustard especially affects sugar maples, red maples and white ash, suppressing growth and possibly interfering with the succeeding generation of canopy trees. I knew it was an invader but a co-worker was informed during a guided walk at Bowman’s Hill Wildflower Preserve of the poisonous nature of the pest.

Garlic mustard is a biennial which means seeds sprout year one and a small plant will grow, the second year that plant will return after winter, bloom and go to seed. It is thought that the best way to interfere with the cycle is to chop it off close to the ground before seeds appear.

The worry about pulling them up is they have a strong, sideways-growing root that breaks when one pulls and if you do uproot the plant you could be disturbing the delicate natives you are trying to save. It’s always something.

Most of your daffodils are probably done by now and just in case you don’t know the way to treat them, snip off the dead flower to reroute energy from seed production to bulb and be prepared to let them stay in their messy clump until at least six weeks have passed for them to reabsorb nutrients from the foliage. If they are in the lawn you may need to inform lawn mowers to go around them or next year’s blooming will be less.

Fortunately the lesser celandine is beginning to fade because people are still asking how to deal with it and there is no way. Thistles are beginning to shoot up where they are a problem and I am suggesting to cut them off and treat with either horticultural vinegar or a blow torch.

Please keep poisons out of the garden.

Happy May.