Diffuse Knapweed

Diffuse Knapweed Diffuse Knapweed BudDiffuse KnapweedDiffuse Knapweed Root


Centaurea diffusa Lam.
Asteraceae (Sunflower family)

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 2nd yr.); occasionally a biennial (needs 2yrs to complete its life cycle).
Flower/Fruit:. Flowers are white to rose, sometimes purplish in color. Heads are many and narrow on the end of each branch. The edges of the specialized leaf (bract) below the flower are divided, like the teeth of a comb. The bracts are tipped with a definite slender spine (important for differentiation from Spotted Knapweed), which makes the flower feel prickly after it dries.
Bloom: Flowers occur from July – September
Stem: Upright, highly branched, 4” to 3 ‘ tall
Leaves: Leaves are covered with short dense hairs. Basal leaves (leaves at the bottom of the stem) are short stalked and often twice divided into narrow lobes, growing to 7 to 8 inches. Stem leaves become smaller in size further up the stem with top leaves being stalkless and less divided.
Root: Taproot (large main root)
Reproduce: Reproduces by seed but may regenerate from the crown if cut and root is not dug up. When the plant dries it can easily break off at the base and become a tumbleweed spreading its seeds. Wind is the primary means by which Diffuse knapweed seeds spread. It can have up to 18,000 seeds/plant.
Seed Viable: Several years, possibly up to 8 yrs.
Mechanical Control: Cutting or mowing the above-ground portion of the plant, before seed set may be an effective way to reduce seed production, but it will not eliminate the infestation. Mowing usually increases diffuse knapweed density, due to increased germination from the soil seed bank. Mowing should therefore be followed by a fall herbicide treatment (Sebastian and Beck 1999). When a diffuse knapweed plant has been cut, the rosette may live and rebolt. Additionally, diffuse knapweed seeds can remain dormant for several years, requiring any cutting program to be repeated several times annually (spring, summer, and fall) to be effective. Mowing or fire can be used as a way to remove standing dead material such that subsequently applied herbicide will be more effective. (Roche’ and Roche’ 1999). Pulling can be effective for knapweed control, but it must be repeated frequently. Youtie and Soil (1994) suggested hand-pulling knapweeds three times annually until the plant disappears. The first pulling is in spring when the soil is moist, allowing enough of the plant to be pulled to kill it. The second pulling in June focuses on bolted plants, with the third pulling just before seed dispersal to kill any remaining plants.
Note: Herbicide Control: Single treatments provide temporary but not long-lasting control.
From CSP – Colorado State Parks (cpw.state.co.us)
Chemical Control: Please go to the links at the bottom of this article for recommendations from Colorado Dept. of Agriculture (Fact sheet pg. 2) and from Jeffco (follow their Link).
Interesting Facts: There are over 400 species of Knapweed. Diffuse Knapweed was brought in from Europe (Mediterranean region). It produces toxic chemicals that can inhibit the growth of desired plants and is a highly competitive plant. Severe infestation (which we have in our mountain communities) result in more than 70% reduction in Elk & Deer forage. May cause a rash in some people.

Diffuse knapweed | Department of Agriculture – Conservation Services
Diffuse Knapweed, Noxious Weed – Jefferson County, Colorado



Thistle Before and After/ Fall & Late Summer Information


1988 July Canada Thistle and deer from Yvonne Micke



1988 Comparison then & now Elk and deer at Rilliet ParkPost Canada Thistle treatment


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 44th or Echter’s on 52nd & 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

Version 2

Dalmatian Toadflax flower
Dalmatian Toadflax flower
Toadflax root system
Dalmatian Toadflax Root

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 1st 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
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

C.A.R.E.’s Future Direction, Call For Nominations

In two weeks we’ll be deciding the future of C.A.R.E. In years past, C.A.R.E. has done so much for our community since its inception in 1987, when it was formed to “…preserve and enhance the community and environment, to promote awareness, and provide a forum for community deliberation…” for the citizens who live in the I-70 corridor of the Foothills west of Denver.

Continue reading “C.A.R.E.’s Future Direction, Call For Nominations”

CARE all-delegate meeting June 16, 2015


In a little over a month all delegates will be meeting to determine the direction of C.A.R.E. for the next year.

As read in the Bylaws (see below), January is when we are supposed to have our annual all-delegate meeting and when we elect new officers for the upcoming year. But so much happens in January, with Holiday travel and weather events, and as a result the annual meetings have shifted from January to June — and this June we’ll be electing a new slate of officers.

The decision-making body of CARE is comprised of delegates from each of the member associations and groups that are within the CARE area. From this body of delegates CARE officers are elected for 1-year terms.

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Activation Ministry Wins Long Legal Battle

Activation Ministry

Canyon Courier, Wednesday May 6th, 2015: Lookout Mountain church wins long legal battle: Way is clear for Gateway on Mount Zion to expand when the Colorado Supreme Court declined to hear the appeal.

At some time in the recent past, Activation Ministry changed their name to Gateway on Mount Zion…


Discover Wildflowers in Jeffco Open Space

From Bailey Becker, Jeffco Public Information Office, 4/03/2015:

WildflowersHave you ever wandered down a trail in your favorite Jeffco Open Space Park and wondered what those beautiful wildflowers were? If you take a Native Plant Master® Course, you will learn not only the names and identifying features of these trailside beauties but also discover interesting facts about their lifestyles, friends and foes. Upcoming offerings include:
•    NPM Course at Mt. Falcon Park on Fridays May 8, 15 and 22, 8:30 a.m.-12:40 p.m.
•    NPM Course at High Plains on Saturdays May 9, 16 and 23, 8 a.m.-12:10 p.m.
•    Plants of Green Mountain: Wednesday, May 13, 8:30 a.m.-12:30 p.m.
For a list of other Native Plant Master offerings, see www.npm.eventbrite.com. Register soon as offerings fill quickly. If you would like to receive notices of future classes, contact npmassistant@jeffco.us.

For information about Jefferson County Extension, visit www.jeffcoextension.org or call 303-271-6620.

Jeffco Expands the Slash Program, Summer 2015

From Bailey Becker, Jeffco Public Information Office, 4/03/2015:

SlashAs we enter into the spring and summer, it is time to start spring cleaning our properties and clearing out our slash, which includes tree limbs, tree tops and pine needles. Doing this is essential to keeping our homes safe and the forests healthy in Jeffco.

You will be able to bring your slash to one of many collections that Jefferson County is offering this year. The slash collection program is expected to run every weekend, except July 4 and 5, from May 30 and 31 until October 24 and 25. Sites are being confirmed and will be announced on the slash web page.

Continue reading “Jeffco Expands the Slash Program, Summer 2015”