Steele: Reduce maintenance by removing noxious weeds

Two invasive  plant species, blueweed and tree of heaven, seen here thriving in a vacant Kelowna lot downtown.  - Gwen Steele/Contributor
Two invasive plant species, blueweed and tree of heaven, seen here thriving in a vacant Kelowna lot downtown.
— image credit: Gwen Steele/Contributor

One of the biggest causes of escalating landscape maintenance tasks is the failure to remove weeds before they set seed or establish extensive root systems.

Last week, I discovered a vacant lot downtown infested with blueweed.

These noxious weeds moved in fast as the lot has only been empty for two years. Some are also growing in nearby gravelled parking lots.

Blueweed (Echium vulgare) is about two feet high and of variable width.

It has masses of small brilliant blue flowers followed by up to 2,000 burr-like seeds. They spread easily as they stick to clothes and animal fur.

The plant looks nice, so is not recognized as a weed until it comes up everywhere the next year.

I also observed many patches of blueweed along the roadsides in East Kelowna. It has the same invasive potential as knapweed so we all need to act now to eradicate it in our area.

Do not put noxious weeds in your green waste bin. Put them into your garbage bin to be buried in the landfill.

For more information and pictures of local invasive weeds search out these websites:, or

In the past, two species of large shade trees have been used extensively for their fast growth.

Both are now considered invasive in many parts of North America.

This month, Siberian elms (Ulmus pumila) ‘snowed’ their millions of white dime-sized discs of seeds all over the valley. The trees can be seen in the small park to the west of the road into Knox Mountain Park.

In July, trees of heaven (Ailanthus altissima) will be topped with a froth of orange/yellow flowers. From late summer to spring they each shed millions of seeds.

The trees look a bit like sumac or walnut but are easily identified by rubbing leaves or bark—both stink, hence the common name, stink tree.

Very bad infestations of tree of heaven can be found on the west face of Knox Mountain in Poplar Point and along the hike to Paul’s Tomb, and throughout Okanagan Centre.

Seeds of both these species are blown everywhere. Because they are tough and need little water they grow almost anywhere. They are often found in cracks in sidewalks and growing against foundations where they are hard to remove. Both are invading the wild, out-competing native species.

With their fast and massive root systems, these two species are a weeding nightmare. Unless they are noticed and removed when very small they are hard to dig out, especially when they have hidden inside hedges or grown up through other plants. Search on Google images to identify their seedlings.

Although not invasive in the wild, in irrigated landscapes maple trees produce many seedlings.

These are also difficult to remove when allowed to grow past seedling size. As with all deciduous trees (ones that drop their leaves in fall), unless all roots are removed, they will continue to grow even when cut down.

Gwen Steele is executive-director of the non-profit Okanagan Xeriscape Association. Learn more about Gardening with Nature and plants for the Okanagan on the website at


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