When is a weed not a weed?

Credit: Elizabeth Rowlands

When is a weed not a weed?

When it’s an invasive plant.

And what’s the difference?

Scientists use a rigorous set of criteria to determine whether a plant is truly invasive, as opposed to being a garden pest. By looking at the degree of reproductive maturity, seed production, length of time seeds remain viable and spreading vegetative structures (runners, rhizomes, etc.), they predict dispersal rates.

And does a plant tend to be spread by humans and/or wild animals? For example, this popular hanging basket plant (Lamium galeobdolon) is now known to be very invasive, choking out native plants in local forests. It has a high rate of human dispersal because people commonly dump out their hanging baskets in autumn. This rampant creeper survives after the petunias and geraniums have frozen, creeping into wild lands.

Whereas a weed is only a problem in gardens and cultivated areas, invasive plants are a problem in wild areas, with far-reaching effects on our natural environment.

With more than 30 years experience in horticulture in B.C. – in wholesale, retail and at VanDusen Botanical Garden for a decade – Carolyn Jones brings a wealth of knowledge and expertise to GardenWise and www.gardenwiseonline.ca as staff horticulturist.