Invasive Plants | Okanagan Xeriscape Association

Invasive Plants Danger

oxatest20 — Thu, 20 Jul 2023 22:26:11 +0000

Gardening with Nature

Article by Sigrie Kendrick

Invasive plants are dangerous for all

Invasive plants reduce biodiversity and pose a significant threat to agricultural crops, habitat for wildlife and fish, and they compromise water quality as well as native plant ecosystems.

These introduced species are non-native plants which have been introduced to our region from around the globe.

Some are toxic to humans, pets, grazing animals and wildlife. They can represent a threat to health and even to life itself.

Often these plants are colourful and attractive, lulling people into not recognizing them for the thugs they are.

I noticed some Echium vulgare or Blueweed at a neighbour’s property several years ago and mentioned that she should remove them immediately. But, she thought the colour was pretty and left them in place. Now she can enjoy an entire hillside of them, with little else in sight.

In addition, invasive plant species depreciate property values and threaten our tourism sector, potentially resulting in huge economic losses.

These introduced plants are able to out-compete our native flora because they do not encounter the same diseases and predators which keep them under control in their native environment.

Many of these invasives have extremely-high seed counts and ingenious methods of dispersing their seeds far and wide. Others have aggressive root systems which spread rapidly.

I have been at war with Cirsium arvense, known commonly as Canadian thistle at my property for the last two decades and was appalled to learn that one plant is capable of producing thousands of seeds which can remain viable for years in the soil.

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Echium vulgare or Blueweed

But, all is not lost. Education is our best defense. We must all pull together to minimize the damage from these nasty non-native plants.

Please take the time to acquaint yourself with the work of the Okanagan and Similkameen Invasive Species Society (OASISS) which has been working tirelessly for the last 25 years to protect the ecosystems of the Okanagan and Similkameen for future generations.

On their website , you will find detailed information on the invasive species to watch for in our area; methods of identification; priority ratings for these plants; and control methods.

Recently OASISS partnered with the South Okanagan/Similkameen SPCA to remove cheat grass and puncture vine from areas used for dog walking around its animal centre. Both of these invasives are extremely dangerous for pets and potentially life-threatening. Puncture vine can even flatten bike tires.

Another resource for education about invasive species is the Invasive Species Council of B.C.’s publication: Grow Me Instead Guide. It makes suggestions for non-invasive alternatives to some of the invasives you may unknowingly have purchased from your local garden centre.

Two that I regularly see for purchase, leading to muttered profanities, are Euphorbia myrsinites, Donkey Tail Spurge, and Vinca minor, Common Periwinkle.

Why are these still for sale at garden centres?

Instead of Donkey Tail Spurge, Grow Me Instead suggests Cushion Spurge, Rock Rose, Broadleaf Stonecrop, or Yellow Ice Plant.

As for periwinkle, consider choices such as Bunchberry, Kinnickinnick, or Lowfast Cotoneaster.

By educating ourselves and working together we can protect our beautiful Okanagan Valley.

Sigrie Kendrick is a Master Gardener and Executive-Director of the Okanagan Xeriscape Association. She can be reached at 778-363-8360 or by email at exec_dir@okanaganxeriscape.org.

The post Invasive Plants Danger first appeared on Okanagan Xeriscape Association.

Reduce Maintenance by Removing Noxious Weeds

oxatest20 — Mon, 04 May 2020 10:49:33 +0000

Article and Photo by Gwen Steele–

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.

I discovered an infestation of Blueweed on the edge of a downtown gravelled parking lot. Like many noxious weeds, they thrive in dry conditions and populate disturbed soil.

Blueweed (Echium vulgare) is about two feet high and of variable width. Masses of small brilliant blue flowers are followed by up to 2,000 burr-like seeds. They spread easily by sticking to clothes and animal fur. It has the same invasive potential as knapweed so we all need to act now to eradicate it in our area.

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

In the past, two species of large shade trees have been used extensively for their fast growth that are now considered invasive in many parts of North America. They are the Siberian Elms and the Tree of Heaven.

Late in May, Siberian Elms (Ulmus pumila) ‘snow’ 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.

This month, Tree of Heaven (Ailanthus altissima) will be topped with a froth of orange/yellow flowers. From late summer to next 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.

Blueweed (Echium vulgare) and Tree of Heaven (Ailanthus altissima)

Very bad infestations of Tree of Heaven can be found on the west face of Knox Mountain in Poplar Point, 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 growing in cracks in sidewalks and against foundations where they are hard to remove. Both are invading the wild, out-competing native species. With their fast growth 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.

For more information and pictures of local invasive weeds search: Grow Me Instead and the Field Guide to Noxious Weeds

The post Reduce Maintenance by Removing Noxious Weeds first appeared on Okanagan Xeriscape Association.

Additional Commentary on Invasive Plants

oxatest20 — Tue, 05 May 2020 11:49:36 +0000

Article and Photos by Mark Godlewski–

Gwen’s article on Removing Noxious Weeds is very interesting and helpful. I have done a bit of research to dig out more information.

The links that she provides are to a couple of older pamphlets, but the Invasive Species Council of BC now has quite an extensive website that can help us to identify invasive species. Here are links to two of the weeds mentioned in the article above: Blueweed and Spotted Diffused Knapweed

You can wander around this site to see other invasive weeds. Personally, I have a lot of problems in my garden with Perennial Pepperweed which I end up pulling out of the beds endlessly. Luckily it pops out of the soil fairly nicely, but if you let a single plant go to seed you are setting yourself up for a sore back next year.

In Gwen’s original version of this article, she mentioned that we should not put invasive plants into the green bin. I checked with the Glenmore Landfill folks and these days they are not concerned at all with invasive plants in the green bins. Apparently the high temperature composting gets rid of all the viable plant material. Interestingly, the two trees Gwen mentions are not listed as being invasive, but they do appear as entries on the Invasive Species Council of BC “Alerts” pamphlet (Fig. 1)

Fig. 1 – List of unwanted horticultural plants posted by ISC

Fig. 2 – Distribution of Invasive English Ivy posted by ISC

Exactly which plants make the full “Invasive” designation seems to be a bit subjective and probably coloured to a large degree by what part of BC you live in.

Some of the “Invasive” plants such as English Ivy are very clearly invasive in the wetter and warmer parts of the province as evidenced by the distribution map (Fig. 2). However, there does not seem to be much evidence of English Ivy invasion in the Okanagan except in close proximity to a garden.

The Trees of Heaven, on the other hand, are widespread located in disturbed native habitat and quite a few gardens. In addition to Knox Mountain, the folks at the RDCO have had a real problem with the Tree of Heaven in Kalamoir Park.

They have chopped down a large grove of these trees that were spreading rapidly by suckers coming off of the roots. The trees were suppressing competition with allelopathic chemicals. You can see the mess that is left and the Trees of Heaven are starting to grow back in the bottom left of the photo (Fig. 3).

They will probably have to spray with herbicide to get rid of them. It is an interesting dilemma because in the right place this tree can look quite attractive (Fig. 4) but there is no doubt that it is highly invasive in the Okanagan.

Fig.3 – Devastation from Tree of Heaven invasion of Kalamoir Park

Fig. 4– Tree of Heaven can be quite attractive in the middle of summer

The Siberian Elm has few redeeming features other than acting as an effective windbreak in the Prairies. It is almost always takes the form of a poorly structured weak tree (Fig. 5). It is much more widespread than the Tree of Heaven probably because its seeds are so common and easily distributed. Almost any ditch or untended lot will contain many little Siberian Elm seedlings and small trees. The younger plants have a distinctive alternating branch pattern and small elm like leaves (Fig. 6). The leaf on a Siberian Elm has two teeth per vein while American Elms have only one.

Fig. 5– A typical form for a Siberian Elm in an open lot

Fig. 6– The distinctive leaves and branch form of the younger Siberian Elms

It is a good idea to be on the lookout for invasive plants on neighbours property as well as your own. Your neighbours may be oblivious to their problem but it could soon become your problem.

Key Horticulturally Invasive Plants

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