Conservation Spotlight: Weeding the Natural Areas

By Sarah ModicBradley, HF&G Natural Resources Specialist

Around these parts it’s not all too uncommon to engage in a conversation about your big weekend plans to… weed the garden beds! Much of the horticulture staff devote countless hours throughout the week to weeding Holden’s precious beds, and then return home to tend to their very own as well. You might be picturing a dandelion, a spiky green leaf in your own front yard, or maybe it’s even between two sidewalk squares (seemingly returning every time you turn around), but how are we deciding who stays and who goes? By my definition, a weed is simply a plant that you don’t want growing in any particular area. Could be an Oak seedling attempting to outshine your vegetable garden or intruding on your marigolds’ coveted space. Your weedy plants are not only seriously affecting the aesthetic of your landscaping, but are also taking valuable nutrients from the soil that should be going towards your higher priority plants. Now what if these weeds were even capable of changing the soil composition so that other plants had less of a chance for survival? That would be one powerful weed.

If you ask a member of the Conservation department that question they’ll likely point you in the direction of the 100+ bags of garlic mustard (Alliaria petiolata) that were collected from Holden’s natural areas throughout this past spring season. Garlic mustard is my nemesis. I can’t un-see it, and you’ve likely seen it too around Ohio or in any Northeast and Midwest state. This guy is one seriously prolific weed. Garlic mustard even takes being a weed to the next level, and has earned the monumental title of Invasive Species, a non-native species that can cause ecological harm. Management takes place from early April to late June as the plant matures from bolting and flowering to seed-set. A single plant can have several thousand seeds in various elongated seed pods, dispersing them onto the forest floor, and can remain viable in the soil seed bank for up to TEN YEARS.

Cheerfully watching the end-of-season haul
decompose in trash bags.

Because this plant has a significant seed bank, it is critical to return to identified locations with an infestation annually to remove new plants. In Holden Arboretum’s natural areas we find garlic mustard in the forest understory and edges. Garlic mustard is well adapted to low light levels, but will also grow phenomenally in light gaps where trees have fallen or have been removed. Areas with high quantities of garlic mustard tend to have low diversity of native herbaceous species, likely linked to compounds released from garlic mustard’s root system. Oh yeah, did I mention this yet? Garlic mustard gets yet another fancy title, allelopathic, meaning the plant produces chemicals that persist in the environment and can negatively affect neighboring organisms, ultimately preventing them from growing. So that powerful weed that disrupts growth patterns to assert its own dominance over the forest floor? Garlic mustard has got that covered.

Flowering second year garlic mustard patch
found in Stebbins Gulch Natural Area.

Despite the annual efforts necessary to manage garlic mustard, it is a relatively simple plant to remove because its shallow root systems makes it easy to pull right out of the soil and slip into a trash bag. It is important to minimize soil disturbance when pulling garlic mustard to avoid stirring the seed bank and encouraging new growth. If you are interested in removing garlic mustard from your own property don’t feel intimidated by its aggressive nature, there are several sites in our own natural areas that have responded beautifully to the continued removal of garlic mustard that now have a bounty of spring ephemerals thriving where garlic mustard once ruled the terrain. The key to management is continued removal, and preventing the seed bank from expanding and the greatest reward from garlic mustard management is spending time in our remarkable natural areas and contributing to their overall health.

Collection of three foot tall flowering garlic mustard plants
found at Baldwin Natural Area.


Sarah ModicBradley is the Natural Resources Specialist with the Conservation department at Holden Forest & Gardens. Sarah completed a Bachelors of Science in Biology at The Ohio State University and went on to pursue a career in conservation. The natural areas at Holden have become Sarah’s favorite place to explore, learn, and manage invasive species!