Knapweed grows along the transmission lines in the Cariboo near Williams Lake. (Jim Hilton photo)

Knapweed grows along the transmission lines in the Cariboo near Williams Lake. (Jim Hilton photo)

FOREST INK: Controlling knapweed one plant at a time

This weed has a very characteristic and showy pink flower

Jim Hilton

Special to the Observer

I think it was about 10 years ago that I first noticed spotted Knapweed at a few spots along Highway 20 and at the entrance of Buckley Drive (the road in to the subdivision where I live).

This spring I made a point of looking more closely for new plants after spotting knapweed blossoms along the road and adjacent trails.

This weed has a very characteristic and showy pink flower, which is often the only way to see the plant which can easily blend in with the native species.

Some plants seem to produce a slender flowered plant the first year but most only establish a small rosette of leaves which establishes a very robust tap root able to quickly produce a very vigorous stalked version the second year usually with many flowers if it has little competition.

I started pulling the plants by hand when they first started producing flowers in May and have been visiting the same sites at least once a week when new blossoms appeared and before they went to seed.

My first visits took about an hour and usually produced about two 20-litre pails of plants which I then dried and later burned in my shop wood stove.

When the ground is wet (which was the case for most of this year) the plants are easy to uproot but a shovel is needed when the soil drys and makes it difficult to remove the plant with its long tap root which is necessary to remove to keep it from reproducing.

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I am still finding some plants in August but it usually only takes a few minutes and I end up with only a handful of skinny plants that have remained hidden until they produce a few showy flowers.

The good news is I think I have managed to severely slow the spread of this noxious weed but the bad new is there are still plenty of new plants and no doubt many seeds that will sprout for probably four more years.


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If I stay vigilant it should only take a few hours each week to keep this weed in check with out spraying.

Knapweed is one of many noxious plants introduced by settlers and later by imported plant products. While these plants are not considered detrimental in their native environment since they have many natural predators to keep them in-check they seem to out compete many native plants by their vigorous growth and in the case of knapweed by a chemical which seems to poison the native plants.

While hand pulling may not be practical in many places where it has been firmly established like many properties along Chimney Valley and along the power lines, I think it has a practical application along with spraying and possibly cultivating and seeding with some aggressive plants like Alfalfa.

Grazing animals seem to help control the Knapweed when they grow along with the more palatable grasses and legumes. It is reported that sheep and goats are good at controlling many introduced weed species.

Jim Hilton is a professional agrologist and forester who has lived and worked in the Cariboo Chilcotin for the past 40 years. Now retired, Hilton still volunteers his skills with local community forests organizations.

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