This article is part of a series from the Sea to Sky Invasive Species Council (SSISC) featuring the highest priority invasive species in the Squamish area. SSISC (www.ssisc.info) is a non-profit society dedicated to minimizing the threat of invasive species in the corridor.
What do tainted milk, tangled fur, intestinal hairballs and Velcro all have in common? That would be the vigorously self-seeding invasive plant known as common burdock (arctium minus).
Common burdock is well known for prickly burs that cling stubbornly to clothing and animals. Its more popular qualities include medicinal and culinary uses, and observation of its hooked spines led to the invention of Velcro in the early 1940s by Swiss inventor, George de Mestral.
Burdock's brownish-green, deep roots are used as a traditional medicinal herb for many ailments, including as a remedy for dry and scaly skin conditions such as psoriasis and eczema, and as a blood purifier clearing the bloodstream of some toxins. In traditional Chinese medicine, burdock is often used with other herbs for sore throats and colds.
Despite the practical uses for burdock, there is a down side. The infamous hook-and-loop system on burdock seeds helps them disperse, hitching rides on passing animals and people, thereby creating new infestations over great distances.
Common burdock is a Eurasian, biennial (or short-lived perennial) herb that tolerates most soil conditions. Plants are identifiable by wavy, heart-shaped leaves that grow alternately on the stem, and purple, prickly flowers borne in clusters at the top. Burdock typically blooms between July and October. Seeds mature by September and are spread throughout the winter and spring.
Common burdock is considered an invasive plant in B.C. and the Sea to Sky Corridor. Invasive plants grow and spread quickly, outcompeting native plants and causing damage to the environment, economy and our health - they are the second greatest threat to biodiversity after habitat loss.
Common burdock is considered a noxious weed under the B.C. Weed Control Act. The burs can cause irritation if they cling to the eyes, throat, mouth, or the inside of the stomach of livestock. In some cases the seeds must be surgically removed. The burs have also been known to ensnare and kill small birds and bats that get tangled up when flying by.
Reaching heights of one to three metres, its large leaves can shade out and prevent other plants from growing, having an adverse effect on crop quality. Burdock also is responsible for tainting milk products if grazed in large quantities. Additionally, burdock plants indirectly affect the development of economically important plants by hosting powdery mildew and root rot.
Reproducing only by seed, each plant can survive up to four years, and seeds two to 10 years. Some studies suggest upwards of 15,000 seeds per plant are produced during its life span.
Now is the time when burdock seeds are mature and ready to spread. If you do find burs on yourself or your pets, make sure to bag them and throw them in the garbage. The best way to remove the plants is to sever the taproot below the root collar (where the stem becomes a root). If you can remove the plants when they are in the first-year rosette stage (i.e. not flowering), that is ideal. Invasive plants should never be composted. Bag the plant and all the burs and take to the Squamish landfill, which is taking invasive plants free of charge this year.
For more information on identifying and getting rid of common burdock, please contact the Sea to Sky Invasive Species Council at [email protected] or (604) 935-7665. More information is also at www.ssisc.info.
