Colorado Dept. of Agriculture Class B Stop the spread
Jefferson County, CO

List B Eradication Required

Aliases: Spreading knapweed, tumble knapweed, white knapweed
Annual: (1yr life cycle). Most commonly a short-lived perennial (survives the winter but doesn’t do well the 2^nd yr.); occasionally a biennial (needs 2yrs to complete its life cycle).

Continue reading “Diffuse Knapweed”

AFTER

Canada Thistle (Late Summer)

You might as well mow the area now (saving the step of cutting the seed heads only).

We can’t stress enough that if you will use a bag on your mower to collect all cuttings, you will greatly reduce the number of seeds left on the ground to germinate next year. If you do not use a bag when cutting, we recommend that you rake the area and bag as many white fluffy seed heads as possible for containment.
Now spray the weed infested area. The before and after pasture picture recently posted, and again here, is a result of a Commercial Spray Company spraying for 3 consecutive years.
As any new Canada rosettes appeared in the interim (and they will) Yvonne spot sprayed the weed using a selective weed killer which she purchases from Abners on 44^th or Echter’s on 52^nd & Garrison (or other smaller garden centers) to insure that she is getting the spray with a 47% formula/active ingredient VERSUS purchasing from the larger box stores where the concentration is milder at 4%. The best reason she uses this concentrate, is that it does not kill her grasses. She follows the directions specifically. and never tries to  mix a stronger solution, as this is a case where “more is not better”.

Musk Thistle (Late Summer)
This late in the season, DO NOT MOW your blooming Musk Thistle! You will just be spreading the seed to form new plants next year. Place a bag over the seed head while you’re digging it up to help prevent the jostling of the seeds. We can’t stress enough, that if you will dig up your Musk Thistle, you will KILL THE PLANT FOREVER. Yes, you will have new rosettes next year from the seed on the ground this and previous years, but you won’t continue to have the same plants.
If you have already cut the seed heads off your Musk Thistle (your neighbors and we thank you) they have most likely been trying to regenerate a new bud (much smaller purple and not necessarily at the top of the plant). Dig the plant up and it’s over. At a minimum, cut the new seed head, bag it and then spray the rosettes next Spring.

If you have mowed your area some time ago, you’ve probably discovered the Musk Thistle has resurged and formed again with numerous patches of rosettes. Remove any buds that have formed and dig them up or spray them now. If you don’t kill the plants/rosettes now, you will continue to deal with more Musk Thistle next year.

The key to weed control is the prevention of seeds. Next spring, before either the Canada or the Musk form a flower bud, spray the Canada, and dig the Musk. If you are going to hire a commercial spray company, start early, they get busy (see our list of recommended spray companies on the CAREjeffco.org web site). Most suggest you spray early spring when the weeds are a few INCHES high. You’ll then be on your way to a Thistle free acreage.

Dalmatian Toadflax Root

DALMATIAN TOADFLAX
Linaria dalmatica ssp. dalmatica
Figwort Family
Colorado Dept. of Agriculture Class B

Aliases: Balkan toadflax, broadleaf toadflax, wild snapdragon, smooth toadflax
Perennial: Forb
Flowers/Fruit: Seeds Mature July – September. (Oct. after the 1^st year)
Flowers: Snapdragon type, bright yellow, tinged with orange,  1-1/2 “ long spur. The upper lip is 2 lobed and the lower is 3 lobed.
Bloom: May – August
Stem: Upright, branching toward the top up to 3-4 ft. tall. A single Toadflax plant contains from 1 to 25 vertical, Floral stems which are thick walled and somewhat woody. Prostrate stems are tolerant to freezing.
Leaves: Light to bluish-green waxy leaves are broad, alternate, ovate, sometimes heart-shaped and upper leaves clasp the stem (an important difference to Yellow Toadflax). Leaves get progressively smaller up the stem.
Root: Roots may grow 20 inches deep or more and lateral roots may extend 10 ft. from the parent plant. Very aggressive.
Reproduce: By seed (500,000seeds or more/plant) as well as by horizontal or creeping rootsystem. Seeds are irregular in shape, tan-gray and 1/24” to 1/16” across.
Seed Viable: 10 Years
Mechanical Control: The combination of spraying and seeding competitive grasses control Dalmatian Toadflax better than spraying alone. Hand Pulling or digging up the roots for an average of 6 years. Plants will re-sprout from root fragments. Spray at flowering or in the fall.
Interesting Facts: It was introduced into the Western US in 1874. Broad leaved Dalmatian Toadflax (L. dalmatica) has been cultivated as an ornamental plant for at least 400 years. Used for centuries as a folk remedy and a dye. Extensive root system outcompetes other plants for nutrients and water. Contains toxic chemicals that can cause liver damage in grazing animals.
Dalmatian Toadflax differs from Yellow Toadflax principally in being larger and having different shaped leaves.
In Colorado, Dalmatian Toadflax shoot density increased over 1,200 percent in six years at one location, and 190 percent over 3 years at another.

Jefferson County Information Sheet Link

Colorado Department of Agriculture fact and treatment Link