Scotch thistles are thriving in the North Okanagan area

They are a nasty, mean-looking plant and they are thriving in the North Okanagan.

Scotch thistle are considered noxious under the BC Weed Control Act, and are a major concern in the North Okanagan and Columbia Shuswap regions.

They can form dense, impenetrable stands that inhibit the movement of livestock, wild animals and people.

The weed is such a concern the Friends of Kalamalka Lake Provincial Park often hold special events to remove the weeds from the scenic Coldstream park.

In many areas of the region, the weed is thriving.

Scotch thistle reproduces through thousands of seeds that remain viable in the soil for more than 30 years.

Seeds also contain a water-soluble germination inhibitor, making it successful in moist areas such as nearby streams and in riparian areas.

Growing up to three-metres tall, Scotch thistle is identifiable by its large, bright violet to reddish flowers that are supported by large spine-tipped bracts.

Woody stems also have spine-edged wings that run up the sides. Leaves are irregularly-lobed, have sharp yellow spikes, and are covered in woolly hairs that give the foliage a grey-green appearance.

Robyn Hooper with the Columbia Shuswap Invasive Species Society, said thistles are a tough plant and once they get established, they are difficult to get rid of.

Hooper said the plants can either be removed physically – cutting them down and digging out the roots – or by using herbicides to kill the plant.

“Mowing alone isn't recommended because you have to get out that tap root,” she said. “Plants can regrow from severed roots and cut stems still may produce viable seed.”

The plants can compete with desirable native species and can reduce wildlife habitat.

Hooper said once an infestation occurs, it often becomes a matter of controlling their spread, than eradicating them from an area.

While the North Okanagan and Columbia Shuswap areas have seen infestations, officials with the Central Okanagan Regional District said there are no significant infestations in that region of the Valley.