Feature Article: Smart Gardening

Invasive Plants are Beautiful, but Harmful Bullies of Biodiversity

Avid gardeners are always searching for new, eye-catching plants to add to their backyard collections. Among these attractions, however, lurk invasive plants that pose a hazard to the environment, the economy, and human health.

The enjoyable tradition of sharing plants and seeds across borders has led to the spread of invasive plants that are sold at local nursery and landscape centres as exotic annuals and perennials. In fact, over 75% of today's invasive plants were intentionally introduced. These two-faced beauties are bullying their way into BC’s fragile ecosystems at an alarming rate.

Invasive plants are the second greatest threat to biodiversity after habitat loss. Due to limited regulation and increased imports, BC gardeners play an important role to help prevent their introduction and spread.

Why are invasive plants a problem?

Invasive plants harm the environment by aggressively out-competing native plants. When these globe-trotting plants arrive in BC’s nurseries and greenhouses, they typically leave their natural pests and predators behind, giving them a competitive advantage to local species.

Having no predators, invasive plants can direct more energy into growing new shoots, spreading thousands of seeds, and capitalizing on open ground. For example, Yellow flag iris (Iris pseudacorus), considered a beautiful aquatic perennial, forms dense patches that displace native plants, alters wildlife habitat and restricts water flow. All parts of this plant are poisonous and can sicken livestock when consumed.

People, livestock and pets can be harmed when coming into contact with invasive plants. Skin irritation, blisters, scarring and severe breathing problems are just some impacts on people. For example, giant hogweed (Heracleum mantegazzianum) can cause severe and permanent dermatitis from the toxic oils in its hairs and sap. In fact, giant hogweed is so dangerous that Work Safe BC has developed a video on safe disposal practices. Yet, this plant made its introduction to BC after catching the eye of gardeners due to its exotic and massive foliage!

Invasive plants have adverse effects on the economy. Property and crop values drop while control costs rise from treating infestations on gardens, rangelands, parks or roadsides. Invasive plants also impede recreation; making trails impassable, damaging fishing streams, and puncturing tires.

The list of invasive plants in BC is growing on an annual basis. Some of the most “unwanted” invasive plants to watch for include: common periwinkle (Vinca minor), English ivy (Hedera helix), Scotch broom (Cytisus scoparius), Dalmation toadflax (Linaria dalmatica), Japanese knotweed (Fallopia japonica), Himalayan blackberry (Rubus ulmifolius or R. discolor), purple loosestrife (Lythrum salicaria), giant hogweed (Heracleum mantegazzianum), and oxeye daisy (Leucanthemum vulgare). Instead of purchasing or transplanting these plants, look for non-invasive alternatives, and notify your local retailer of their impacts.

Be informed on invasive garden plants:

Making informed choices on what you grow in your garden will help keep your yard free of invasive plants year after year, so you can concentrate your efforts on the non-invasive species that add beauty, without the battle.

1. Determine whether a species is invasive before purchase, and select suitable alternatives. Ask your nursery if plants are “fast spreaders” or “vigorous self-seeders;” usually these are signs of an invasive plant.

2. Watch out for wildflower and birdseed mixtures that contain invasive plants. Buying the components separately and mixing them yourself is the only way to be sure of what you are scooping into your feeders or spreading in your yard. Read the label and ensure that the species listed are non-invasive and desirable for your location. Consult with your regional invasive plant committee, local bird expert or naturalist club to determine if the seeds listed in the wildflower or seed mixture are invasive.

3. Ask your local invasive plant committee or regional district for guidance by visiting www.invasiveplantcouncilbc.ca for contacts and more information, and/or check www.greatplantpicks.org.

Five simple ways you can help:

1. Avoid walking/driving/riding through invasive plant infestations.

2. Remove seed and plant parts from clothing, pets, vehicles, and equipment, and dispose properly by bagging invasive plants for the local refuse site. Be sure to inform the landfill operator that you have invasive plants and not regular yard waste.

3. Avoid letting invasive plants fruit or set seed, as birds, animals and humans can spread the seeds.

4. Avoid picking plants from roadsides; many of the prettiest wildflowers are aggressive invasive species.

5. Learn how to identify and report invasive plants in your community.

Taking the time to learn some strategies is an excellent way to meet other gardening enthusiasts, and don’t forget to pass these insights on to your neighbours. Help stop the spread of invasive plants—“spread the word not the weed!”

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