Sunday, May 5, 2013

Noxious Weeds Problems in Jefferson County Colorado by Gina Kokinda

Myrtle Spurge (Euphorbia myrsinites) photo courtesy CSU
Do you have a noxious weed problem? I do. The snow is melting, and so again begins my battle with the dreaded knapweed (and thistle -- among others) that persistently aim to diminish our little slice of homestead heaven. When we purchased the place in Evergreen years ago, I didn't even know what knapweed was. These days, it is the bane of my summer gardening fun. I have disposed of countless bags of it (at the local landfill), yet it persists with vigor each passing year. In fact, I'm realizing that if we want home grown vegetables this season, we'll definitely need the help of a contractor to control the weeds.

It is important to be aware of the weeds on  your county's noxious weed list. Noxious weeds threaten biodiversity and ecosystem stability with their aggressive behavior, stealing precious moisture, sunlight and nutrients from the surrounding native species, upon which our pollinators depend! If left unmanaged, they will literally take over a property and invade others in the neighborhood.

Scotch Thistle (Onopordum acanthium) photo courtesy Idaho Weed Awareness
 Did you know that one Scotch Thistle plant can produce up to 40,000 seeds, which can remain viable in the soil for over 30 years!?

Purple Loosestrife (Lythrum salicaria) Photo courtesy
Did you know that one One Purple Loosestrife plant can produce 2-3 million seeds per year, remaining viable up to 20 years.

In controlling noxious weeds, the key, obviously, is to not let them go to seed. Eradication and reseeding with a competing native perennial grass or 'weedy' native are as important. Knowing the weeds and their lifecycles, and using an integrated approach to control are crucial!

Diffuse and Spotted Knapweed (Centaurea stoebe) Photo courtesy Oregon State University
Diffuse and spotted knapweed are categorized as List B - Eradication Required on Jefferson County's noxious weed list. Diffuse knapweed is an herbaceous biennial in the Sunflower (Asteraceae) family. Dried plants break off at the base and act as tumbleweeds, spreading seeds (15,000+ per plant), which can stay dormant in the soil for more than six years. Spotted knapweed plants are perennial. Also in the Sunflower family with the same methods of reseeding, each plant can produce as many as 40,000 seeds, which can stay dormant for eight years. Pulling them after they flower requires gloves, as they can cause skin irritation and itching. The two can generally be found in the same areas and can be managed similarly.

See this CSU extension fact sheet for control of diffuse and spotted knapweed, plus other noxious weed information and valuable links here:

Small Acreage Management Weeds Resources

Colorado Noxious Weed Information

For something much more fun on weeds, check out this humorous weed story from a old blog post by Carol King.