Weed of the Week: Oxeye Daisy

During the summer months, whether you enjoy a stroll or a bike ride along the meadows and roadside paths of southern or interior British Columbia, you’re likely to notice an attractive abundance of oxeye daisies (Leucanthemum vulgare) in bloom. Many people consider oxeye daisy to be a pretty wildflower, but wildflower does not mean native; in fact, oxeye daisy is not a native wildflower in BC, but an invasive plant.

With origins in Europe and introduction in the 1800s, it’s easy to see why people believe oxeye daisy is a native wildflower. Oxeye daisy is actually an out-of-control perennial, considered regionally noxious under the BC Weed Control Act. Invasive plants grow rapidly and spread quickly, causing damage to the environment, economy and our health. They are also the second greatest threat to biodiversity after habitat loss, according to the International Union for Conservation of Nature (IUCN).

In Greek mythology, the name ‘oxeye’ was a flattering name affectionately given to Hera, the Queen of Olympian gods and later given to this pretty daisy. Despite its beauty, this invasive plant can greatly alter the productivity of a pasture by replacing grasses, especially in an overgrazed area with low soil fertility, thereby creating economic losses. Worldwide there are about 200 species of daisy that the Scots called "gools". The farmer with the most gools in their wheat field paid an extra tax. Due to its unpleasant taste, most grazers avoid this plant, leaving it to spread easily within grazed grasslands, pastures, and rangelands. Infestations decrease forage for wildlife and local plant biodiversity.

Even if some plants are eaten, as many as 40% of the seeds consumed by cattle may remain viable after passing through the digestive tract. Tests have shown that 82% of buried seeds remained viable after six years, and one percent were still viable after 39 years. These plants have also shown to carry several crop diseases including the yellow dwarf virus of potatoes.

Oxeye daisy plants aggressively reproduce by seed and underground stems. A single plant produces 26,000 seeds and dispersal from parent plants lead to new, dense infestations that quickly spread. Commonly found dotting low to mid-elevations in grasslands and dry to moist forests, this unwanted invader is present in the Kootenays, Lower Mainland, Vancouver Island, and of major concern in the Cariboo, Okanagan, Peace River, Thompson, and Omineca. Oxeye daisy is a considered an invasive plant in 13 crops in 40 countries!

Oxeye daisy has daisy-like flowers at the end of course, slender stems, with lower spoon-shaped leaves. The young leaves are said to be eaten in salads in Italy. Central yellow disks grow 10-20 millimetres wide and white ray flowers 1-2 centimetres long. Oxeye daisy is often confused with the ornamental Shasta Daisy (Chrysanthemum maximum), which has larger yellow disk (2-3 cm) and white ray flowers (2-3 cm).

Shasta daisy is a good alternative to oxeye daisy, and if you want to bring nature back to your garden with wildflowers, try to choose wildflower seed mixes carefully, as many contain invasive plants like oxeye daisy. Wildflower mixes do not tend to list the species they contain, and colorful photos on package covers mislead consumers into purchasing invasive plant seeds that are native to Europe and other parts of North America, but not BC. Avoid wildflower mixes unless you are buying them from a reputable native plant nursery that has collected seeds locally.

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