Common Burdock

Arctium minus

Non-Listed Invasive Plant

General

Native to Europe
Other common names include lesser burdock or wild rhubarb.
Best known for the hooked bristles on its burs that stick to fur and clothing, and inspired the invention of Velcro.
May be confused with greater burdock (Arctium lappa) which is similar in appearance but larger in size growing up to 9 feet tall, larger flower heads, and the petioles of rosette leaves are solid. Greater burdock has flowers on long stalks while lesser burdock flowers are stalkless or on short stalks.
Common burdock is a secondary host for pathogens, such as powdery mildew and root rot, which can spread to economically important plants.
Considered toxic due to potential diuretic effects, there are also reports of allergic reactions when the hooked bristles of burs lodge under the surface of the skin.

Identification

A large leaved, coarse biennial that grows as a rosette of leaves the first year and then produces a 2 to 6 foot tall, erect, flowering stem.
Rosette leaves are large in size, up to 20 inches long and 12 inches wide. Leaves are broadly ovate to cordate with a heart-shaped base and wavy edges, resemble rhubarb leaves. Upper leaf surface is dark green while the underside is a pale gray-green and wooly. Lower leaf stalks (petioles) are hollow.
Stem leaves are similar but smaller than rosette leaves. Stem leaves are alternately arranged, and decrease in size going upward towards the tip of the stem. Both stem and rosette leaves are petiolate, with a purple tinged leaf stalk.
Stem is rough and hairy, hollow, and grooved lengthwise. Flowering stems emerge in June.
Flower heads are located at the ends of branches, comprised of a round ¾ inch wide bur with hooked bristles beneath a closely packed cluster of tubular, reddish-purple, pink and sometimes white flowers. Flowers are similar in appearance to bull thistle (Cirsium vulgare). Flowers form from July to October.
Each bur contains many single-seeded, brown, oblong fruits that are attached to a stiff bristle.
Root system is a very large, thick, fleshy taproot that has a brown, corky, shredded surface. Roots are often 2 feet in length.

Photos

Habitat

Grows in full sun to partial shade.
Common burdock is found in a wide range of soil conditions from sandy clay to moist loam. Prefers nitrogen-rich soils.
Occurs in disturbed areas such as roadsides, stream banks, woodland edges, lawn edges, waste places, abandoned farmsteads, and pastures.

Reproduction and Spread

Reproduces by seed only, generally considered to be a biennial, can behave as a perennial and take four or more years to flower.
When burs dry, their hooked bristles attach to fur or clothing and the bur separates from the plant thereby dispersing its seeds. Seed dispersal begins in September and continues throughout winter into the following spring.
Common burdock is a prolific seed producer, on average a single plant produces 15, 000 seeds.

Control

The key to controlling common burdock is to limit seed production and prevent further spread.
Hand-pulling or digging can be effective for small infestations in their first year basal rosette. Make sure to dig out the entire taproot.
Cutting the stem at the base and digging up root after plants bolt but before flower buds develop may be effective.
Mowing can be effective after plants have bolted but before flowering. Buds can re-form after cutting, so monitoring and follow up treatment will be necessary.
Cultivation is an effective method, but limited to certain areas.

Chemical Control

Herbicides are most effective when used at the rosette stage. If plants have gone to seed, treatment is pointless as plants are generally biennials and will die after seed production with our without herbicide.
Herbicides containing the following active ingredients are effective against common burdock:
- Glyphosate
  - Foliar application before flower buds develop or to actively growing plants in the rosette stage.
  - Rate 4.5 to 7.5 pints per acre. 1% to 2% solution assuming 50 GPA.
- 2,4-D
  - Foliar application before flower buds develop, plants should be actively growing at time of treatment.
  - Rate 2 lb acid equivalent per acre. Read product label for mixing equivalents.
- Aminopyralid (Milestone)
  - Foliar application apply to actively growing plants in the rosette stage.
  - Rate 4 to 6 fluid ounces per acre. 0.08 to 0.12 fluid ounces per gal of water. Equivalent to 0.06% to 0.09% solution, assuming 50 GPA.

Works Cited

The Ohio State University, Ohio Weed Guide. (2020). Common Burdock (Arctium minus). Retrieved April 6, 2020, from https://www.oardc.ohio-state.edu/weedguide/single_weed.php?id=16
Bebeau, G. D. (2014). The Friends of the Wild Flower Garden, Inc. Plants of the Eloise Butler Wildflower Garden The oldest public wildflower garden in the United States. Retrieved April 6, 2020, from https://www.friendsofthewildflowergarden.org/pages/plants/burdock.html
Montana State University Extension. (2017, June). Monthly Weed Post. Common burdock (Arctium minus). Retrieved April 6, 2020, from http://msuinvasiveplants.org/documents/extension/weed_posts/2017/June 2017 Weed Post_common burdock.pdf
Pacific Northwest Pest Management Handbooks. (n.d.). Burdock, common (Arctium minus). Retrieved April 6, 2020, from https://pnwhandbooks.org/weed/problem-weeds/burdock-common-arctium-minus