Habitat Restoration December 2021

Weed of the Month-Common Mullein (Verbascum thapsus)

A big part of moving from fall into winter for the habitat program is prepping for the spring. Treating or removing multiyear invasive plant species before their reproductive stage saves the program time and reduces herbicide usage. Many of our invasive species spend their first year as rosettes, or stay active through the winter, making them easier to locate and identify. Late fall/early winter is also a good time to break out the propane torch as an alternative to herbicide, or digging, for those pesky multiyear species. Over the next few months I’ll share treatment approaches to some of our common invasive species that we target through the colder wetter months starting with common mullein. Mullein exploded in the oak restoration area post-logging and is easily spread by the tracks of equipment. If you find a plant or two in your yard take a look at its medicinal uses and see if it is something you could utilize, just know that if there is bare disturbed ground anywhere around the mullein plant will find it and in a short period will become the dominant species.

Common Mullein is a biennial forb native to Eurasia and Africa. In the Northwest it is considered an invasive species because it spreads quickly and can create monocultures in disturbed open areas. The plant has many medicinal uses and is a good pollinator plant, but on the Refuge we work to remove it because of its aggressive spread and ability to out compete native plants species.

Mechanical removal is an option for new or small patches, and it can be pulled or dug out depending on soil and plant stage. We usually leave the plant where it was removed but expose the root system to drying by upturning or laying across a downed log. Mechanical removal works for either 1^st or 2^nd year plants.

Herbicide treatments are used on the Refuge when patches are extensive. Best treatment practice is to spray 1^st year rosettes, or 2^nd year plants before the center stalk has bolted. We found a silicone surfactant works best with a broadleaf herbicide, but glyphosate will work if surrounding vegetation is expendable. Silicone surfactants can not be used when plants are in flower.

If treatment is delayed and the center stalk has bolted, we will cut and bag the stalk if it has seeds, then dig out the plant because it will repair the stalk, reflower, and set more seed. Because the Refuge has trained licensed sprayers we have access to more herbicide options. I recommend homeowners stick to mechanical removal when possible and quickly rehab sunny disturbed soil sites.