Invasive species


Thanks to those of you who have taken the time to call or email with questions and ideas for future articles. I’ve been asked to outline some of the redeeming qualities of these much maligned plants.

Many people seemed surprised that I am aware of the many virtues of these plants that we love to hate. But I’m of the belief that every plant has its purpose and possesses unique properties.

To the average person, the term ‘weed’ connotes a good-for-nothing, unproductive plant, which competes with crops or garden plants for water and nutrients. Weeds generally have negative connotations because they are growing in areas where people do not want them to be and because they grow relatively fast and invade where other plants are trying to grow.

However, many plants classified as noxious weeds have medicinal value and in some cases these qualities are the root cause for the plant’s existence in Canada. Even the ubiquitous dandelion – now recognized as an important source food source for pollinators in spring — has been used for centuries to treat liver, gall bladder,

kidney and joint problems.

In some countries, dandelion is

considered a blood purifier and is used for ailments such as eczema and cancer. Dandelion has also been used to treat poor digestion, water retention, and diseases of the liver such as hepatitis.

While it technically is a weed, dandelion does not rank high on my list of priority weeds. There are some highly aggressive species that pose a threat to our natural

environments, yet posses astonishing

medicinal benefits.

The weed that surprises most people in the Okanagan-Similkameen region is

St. John’s-wort. This particular perennial is widely known for its anti-depressant properties.

However, its dominance as an invasive plant in grasslands and open coniferous forests is not so widely recognized. In

ancient times, herbalists wrote about its use as a sedative and a treatment for malaria, as well as a balm for wounds, burns and insect bites.

Today, St. John’s-wort is used for depression, anxiety and sleep disorders. These same chemical constituents depress the central nervous system of grazing animals and increase their sensitivity to temperature change and handling. St. John’s-wort also affects the liver of grazers, causing temporary sensitivity to sunlight. Fortunately, livestock usually avoid it

unless food is scarce.

Burdock is a tenacious invasive plant in our region that has leaves resembling those of rhubarb in size and shape.

Flower heads are round and thistle-like, with numerous, small purple-hued, funnel-shaped blooms in mid-summer to early fall. Blossoms are surrounded by stiff, prickly, hook-tipped burrs that grasp and hold firmly to clothing and fur.

Medicinally, this weed aids skin

disorders, such as boils, acne, eczema and psoriasis. It also acts as a tonic to the

digestive system and is a wound healer.

Herbalists also value several thistle species. The roots of bull thistle — a biennial with deeply cut and prickly leaves with long yellow spines — have been used as a poultice and a decoction of the plant used as a poultice on sore jaws. A hot infusion of the whole plant has been used as an herbal steam for treating rheumatic joints. The root of Canada thistle – a perennial with dark green, wavy leaves — has been chewed as a remedy for toothache, while a decoction of the roots has been used to treat worms in children.

A leaf tea made from Canada thistle is used as a tonic and

diuretic and has been used for tuberculosis. Externally, this thistle species has been used for skin eruptions, skin ulcers and poison-ivy rash.

And lastly, who would have ever guessed that puncturevine – the summer annual with spiny seedpods strong enough to puncture a bicycle tire – has a huge list of medicinal qualities.

Considered an important diuretic herb in Ayurvedic (India) and Chinese medicine, it is recommended for urinary problems,

kidney and lower back pains and as an aphrodisiac. It also increases testosterone levels and is consequently used by

bodybuilders as a natural alternative to chemical anabolic steroids.

Then, there is cheatgrass beer. Not exactly medicinal value but an interesting discovery nonetheless. Researchers have discovered that cheatgrass seed has similarities in biochemical composition to barley.

So the next logical step was to try and brew it. They produced a 4.5 per cent alcohol beer that went through a panel of taste testing and was recorded as a flavourful consumable product, similar to amber ales. Who would have thought?!

So next time you are toiling in the garden pulling weeds, you might think a little bit differently about those unwanted plants.

For information on invasive species go to our website: or contact the Program Coordinator for the Okanagan-Similkameen, Lisa Scott, at 250-404-0115.

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