After the storm earlier this week, snow blankets the fields, hiding most signs that anything ever grew there. But interspersed with the even white blanket and occasional dried grass leaves are spikes, sticking up like posts in the empty landscape. We’re finally noticing the dead and dried flower/seed stalks of Common Mullein (Verbascum thapsus).
Mullein arrived from Eurasia along with the European settlers. They used the flowers to make tea and the leaves to treat rashes and burns. Smoking the dried leaves was also thought to cure bronchitis. Even today, a quick online search produces a multitude of sites devoted to mullein as an herbal remedy.
The introduced plant thrived in the New World, and has now naturalized in all 50 states plus southern Canada. A deep taproot helps it to survive drought and its extreme hardiness allows it to overwinter in even the coldest climate. Mullein prefers disturbed soil, and can’t compete with native vegetation in natural areas.
Like most Verbascums, Common Mullein is a biennial. The first year it produces a big rosette of soft, fuzzy green-gray leaves, reminiscent of Lamb’s Ears. During the next growing season, it elongates, then sends up a towering flower spike that can reach to six feet if conditions are favorable. The individual flowers are “school bus” yellow, with five petals, and are an inch or so in diameter. They’re even rather pretty.
But then all those flowers turn into seed pods. Each and every mullein plant can produce between 100,000 and 250,000 seeds! While some will sprout the following spring, others can remain dormant but viable in the soil’s seed bank for up to 100 years.
This prolific nature, along with the fact that livestock won’t eat it, have landed Common Mullein on both Hawaii’s and Colorado’s noxious weed lists (and on those of individual counties in several other states). According to Colorado law, this prolific weed is required to be “eradicated, contained, or suppressed” by landowners (details vary by locality). However, if you look around at all the dead flower stalks, it’s obvious that we’re not doing a very good job. Even the local county parks are full of mullein plants!
That’s a bit surprising, since with persistent effort, mullein is relatively easy to control. The rosettes can be hand-pulled, even with their long root, or you can slice them off at the soil surface. If you overlook them the first year, they’ll be much more noticeable when they bloom, and you can lop off the flower stalk the second year. (Doing this too early in the season can prod the plant into a second attempt at flowering, so be vigilant.) Or course, herbicides work too. The goal is to keep them from maturing a new crop of seeds.
Not all mullein species are considered invasive. I was shocked to see mullein growing in the Denver Botanic Gardens (shown above) until I learned that other Verbascum species are much better behaved than V. thapsus. They even come in other colors, including pink and white. For example, Wavy-leaf Mullein (V. undulatum), shown below, offers a profusion of brightly colored flowers every summer.
Finally, while we may fight the mullein invasion, some bird species are happy to take advantage of this widespread food source. Both American and Lesser Goldfinches, in particular, can be found nabbing seeds from the stalks in late summer.