What is horseweed?
Erigeron canadensis, also known as horseweed or Canadian fleabane, is an annual to biennial wildflower native to North and Central America, that is now considered a weed. It naturalises in waste ground and colonises uncultivated soil. It can grow up to between 50cm and 1.5m tall and produces tiny white flowers with yellow centres between June and September.
How to identify horseweed
Horseweed has tiny white flowers, bristly stems and narrow, hairy leaves. It has a carrot-like scent. Seeds can germinate in the autumn or spring. Autumn seedlings develop a rosette of leaves, which overwinters and resumes growing in spring.
How it causes problems
Each horseweed plant can produce up to 60,000 seeds, which are dispersed by the wind and germinate in the autumn. If left to self seed, it will quickly multiply and compete with ornamental and native wild plants for water and nutrients.
Horseweed and the law
Horseweed is not listed among those plants regulated under UK law, but it is noted by the RHS as having the potential to become a nuisance. Potentially invasive plants are usually plants that are either very vigorous or have the ability to spread easily.
How to control horseweed
Dig over the soil and remove any rosettes in the autumn. As the Erigeron canadensis life cycle is an annual one, the best method is to dig or pull it out before it has a chance to set seed.
Frequently asked questions
Should I pull horseweed?
Yes, pull or dig it out before it finishes flowering. This will prevent it from dispersing its seeds and creating new plants.
Is Erigeron canadensis good for anything?
It was used by Native American in animal bedding to prevent fleas – hence the name ‘fleabane’. Other uses of Erigeron canadensis have in the past included medicine and food. Native Americans have used it as a herbal medicine for illness such as dysentery, and to treat wounds. Horseweed has also been used in cooking – the leaves were used dried to add flavour to dishes such as soups and stews.
