A team of volunteers has been clearing bamboo at Broad Branch Stream. That’s not the only invasive species they are battling. John Burwell of the Pinehurst Project tells us what’s on their radar now:
This is Tucker Harris, of Ingleside at Rock Creek Park.
She has been part of the Pinehurst Project volunteer effort at Broad Branch. She’s been busy removing English ivy from trees, but now that spring is here, removing garlic mustard (Alliaria petiolata) is more important.
Garlic mustard, a Class A noxious weed, is a biennial or winter annual herb that generally grows two to three feet in height, and sometimes as tall as six feet. It is allelopathic, producing chemicals that inhibit the growth of other plants and mycorrhizal fungi needed for healthy tree growth and tree seedling survival. Garlic mustard is a threat to the diversity of many native ecosystems. Invasions have a very dramatic impact on the ground layer flora, strongly reducing abundance of native plants, more from this chemical warfare than from direct competition.
This plant gains a foothold in fields and forests by emerging earlier in spring than many native plants. By the time native species are ready to grow, garlic mustard has blocked their sunlight and outcompeted them for moisture and vital nutrients.
Removal efforts need to be continued for several years to eliminate the seed bank, those seeds that remain in the soil. They may not germinate until conditions are ideal. Plants must be pulled, bagged and disposed of to prevent further seed dispersal.
Garlic mustard was introduced to North America by European settlers in the 1800s who used the herb for culinary and medicinal purposes, and as the name suggests, it has a garlic-like smell and a mustard-like taste. On average, a garlic mustard plant will produce 22 siliques (seed pods), each of which can contain as many as 28 seeds. A particularly vigorous plant may produce as many as 7,900 seeds, although the average is more likely to be in the 600-seed range. The seeds generally germinate within one to two years, but may remain viable for up to five years in the seed bank. Seed dispersal is mainly by humans or wildlife.
English ivy does remain a threat. It must be removed as the stress from the added weight of rain, snow, ice and wind resistance can be a contributing factor in toppling trees. And you can help the volunteers eradicate both English ivy and garlic mustard by taking note of what is growing in your yard. Rock Creek Conservancy asks residents to take the ivy pledge and remove the plants from their properties.
To join the volunteer efforts at Broad Branch Stream, contact John Burwell at [email protected].
Brian Lewis says
There is some debate on “bothering” to pull garlic mustard. As cited in a Cornell university study. I am kinda confused – as I know it is to be pulled, bagged, and disposed into refuse only – not as a bio mass collection for turning into compost.
What do you reccomend?
Alex S. says
Like many matters involving natural resource management, it’s a matter of priorities. I wouldn’t, for example, prioritize clearing the area in the 2nd image. It’s largely vinca, garlic mustard and wineberry- all invasives. But an area with significant biodiversity that hasn’t been overwhelmed with garlic mustard would be worthwhile if one can minimize disturbance.
You are correct that pulled garlic mustard should be bagged and disposed of as refuse. Once the plants bolt, the seeds can continue to mature even after being pulled. So pulling and leaving them on the ground doesn’t help that much. The plants can also re-root. It should not be used in compost.