What to do with all the weeds?

By Michelle Le Blanc, Coordinator

San Luis Valley Weed Management Association

The extra moisture this past season pulled a lot of weeds out of dormancy. Weeds don’t stay in town, because their seeds are easily dispersed by wind, water, shoes, pets, and birds to surrounding farms, ranches, and waterways.

In the San Luis Valley, it is estimated that invasive weeds cost private landowners, the public, and federal lands at least $1.2 million in agricultural production, wildlife habitat and recreation. Therefore, it’s important to stem the tide of invasive weeds’ spread.

While you have to abide by your county or town ordinance for weed management, here are a few tips that can help make each year progressively easier.

First, don’t let weeds flower and go to seed before you treat or pull them. You will save yourself tons of time next year if you spend some time this year getting rid of them before they can reproduce.

Second, I find that watering the area where I’m going to pull weeds the night before helps loosens the roots (and saves my back). Water for about an hour, let the soil soak up the water overnight, then loosen the soil with a shovel, and pull. Remember to wear gloves, bag up the weeds, and toss in the trash.

Third, ask for help. I’ve had my share of weed problems over the years and have been lucky to have friends help me. The promise of shared time, a home cooked meal, and a tasty beverage will go a long way in getting some help and making the task less onerous.

Fourth, not all treatments work for all weeds, so do some research. Some weeds really do require chemical herbicide, because pulling or mowing simply creates new plants. Most likely, though, consistent effort to keep weeds from seeding works best if done throughout the season and over many years. If you don’t know what a weed is or how to get rid of it, go to www.slvnoxiousweeds.org, www.colorado.gov/ag/weeds or www.cwma.org to see if you can find a match. These websites also have treatment recommendations. You can also call or visit the Colorado State University Cooperative Extension service.

If you don’t want to use chemicals, you can try a vinegar spray. Mix a gallon of white vinegar, one tablespoon of dish soap, and one tablespoon of cooking oil, and spray the weeds when it’s hot and sunny. This will kill the leaves, stress the plant, and possibly kill it, but the roots may not die. I’ve used it and it (mostly) works, but I’ve found that I have to spray several times a season.

Here are some of the most common weeds found in towns around the San Luis Valley.

Common Tansy – often found in flower beds, this perennial plant reproduces by both seed and creeping rootstocks. Control this plant through repeated mowing or cutting. Tilling will cause common tansy to spread. Wear gloves and goggles, because tansy can be toxic.

Common Tansy

Common Tansy

Dalmatian toadflax – looks like yellow snapdragons, but shouldn’t be planted in your flower beds. Pulling is effective on small infestations and if done every year for 5-6 years.

Hoary cress – is also known as whitetop. One plant can produce from 1,200 to 4,800 seeds. The plants emerge in early spring with stems emerging from the center of each rosette in late April. Hoary cress flowers from May to June and plants set seed by mid-summer. Mowing combined with chemical treatment stresses the plant and keeps it from going to seed.

Refuge hoary cress

Hoard cress is a noxious weeds which loves bare ground.

Quackgrass – grows from underground rhizomes to a height of 1 to 4 feet with erect stems. Till to the middle of the stand and prevent it from going to seed. Like other weeds, it is wise to find something to out-compete it like a desired grass or ground cover.

Tamarisk or salt cedar –is beautiful, but it uses about 200 gallons of water a day which is very dangerous in our arid climate. A bulldozer or prescribed fire can be used to open up large stands of salt cedar. These methods must be followed up with an herbicide treatment of the re-sprouts when they are 1 to 2 meters tall. Chainsaws, or loppers for smaller plants, are effective for cut-stump treatments to smaller infestations or in environmentally-sensitive management areas.

Salt cedar (tamarisk) List B:

Salt cedar (tamarisk) List B: Courtesy Colorado Dept. of Agriculture

Russian olive – with silvery-green leaves and a scent like heaven, these trees are beautiful but demand a lot of water. Replace Russian olive trees with native trees and remove seedlings and saplings before they mature. Stumps respond well to a long, hot burning fire or herbicide treatment.

Russian olive

Russian olive: List B Elaeagnus angustifolia

Yellow toadflax – The showy snapdragon-like flowers are bright yellow with a deep orange center. It develops an extensive root system, making control options varied. Pulling is not recommended due to the extensive root system, but several chemical options are available.

Yellow Toadflax

Yellow Toadflax

Bindweed – has arrowhead shaped leave that grow on a long vine close to the ground. Trumpet-like flowers range from white to pink. Persistent stress to this plant as well as healthy grasses will help manage this weed.

Common mullein – this one hurts me because it’s so beautiful and I love it stalk of sulfur-yellow flowers with my fuchsia hollyhocks, but again, mullein produces so many seeds that it can take over an area in a short time. Hand pull or dig when soil is moist, prior to flowering and seed production can be effective.

Cheat grass aka downy brome – is a major fire hazard. This grass grows in the understory of the forest and fuels very hot and hard to fight fires. You can mow it, graze it, till it to control it as long as the seed heads are purple; when the seeds turn green or yellow, it’s too late. To eradicate, plant desirable grasses and maintain appropriately.

If you have questions about weeds or weed management, contact the SLV Weed Management Association Coordinator at 719-588-3268 or via email at slvwma@gmail.com. Our website is www.slvnoxiousweeds.org. Information is also available through the Colorado Weed Management Association’s website www.cwma.org and the Colorado Department of Agriculture’s website www.colorado.gov/ag/weeds. Photos courtesy of Colorado Department of Agriculture.

The SLV Weed Management Association is a public and private partnership created to promote awareness and management of noxious weeds through local and regional initiatives in the SLV area with the vision to cooperatively manage and/or control noxious weeds throughout the San Luis Valley Management Area regardless of geographic or political boundaries to promote ecological and economic values.


Posted in Noxious Weeds

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