Spotted Knapweed Must Die

A friend once remarked to me, after hearing me complain about battling knapweed on my undeveloped property: “If something is green and it grows, I don’t worry about it.”  I can still see him shrugging his shoulders.  “It’s green,” he emphasized once more, “that’s all that matters.”

I have always been the overly-sensitive worrier of the bunch.  As a kid, I checked the exact air pressure in my bike tires with a gauge while everyone else checked by squeezing the tire for firmness.  I sacrificed pleasure spending in favor of auto insurance during high school.  Today, zika virus is on my radar.     

But spotted knapweed is something my friend, you, and I all need to worry about.  Spotted knapweed is insidious.

Knapweed is an invasive biennial or perennial that looks similar to a bachelor’s button flower.  Originally from Eurasia, spotted knapweed thrives in Montana’s sunny and well-drained landscapes—especially our wildlands and wildland interfaces.  A knapweed plant might reach up to five feet in height in favorable conditions.

Here is the big problem.  Spotted knapweed is a killer.  This weed quickly creates a monoculture and eliminates competition from grasses and forbs by distributing its own natural herbicide called “catechin.”  Equally as disturbing, an average knapweed plant produces 25,000 seeds.  These seeds might remain viable on the ground for up to eight years.    

Knapweed, if given a chance, will absolutely take over.  Our range animals and wildlife do not prefer to eat knapweed.  And when spotted knapweed was accidentally introduced to North America over a century ago, its natural controlling enemies—mostly insects—did not arrive with the weed.

While pulling spotted knapweed and some biological agents (introduced insects) can be helpful in controlling small infestations, large invasive cultures must be sprayed with herbicide.  I am no fan of herbicides as a general rule, but spotted knapweed must die.

I have been battling knapweed at my mountain property for many years.  Tomorrow, I am meeting a contractor to arrange for some “selective spot” spraying on a few new “flares” of knapweed.  I have posted a couple of photographs of knapweed for those of you unfamiliar with this weed.

--Mitchell Hegman

PHOTOS: mtweed.org