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Fall Weed Management

As the weather begins to turn cooler, the Rangers are planning their fall weed management activities. The two most important seasons are the spring when plants begin their growth cycles and the fall when they are shutting down and storing reserves for the winter.

Fall weed spraying can be very effective since plants can transport herbicides to their roots. Species targeted in the fall are deeply rooted perennials like Canada thistle, which requires several management strategies in order to achieve control. Herbicides like Plateau are applied in fall to prevent weedy annual grasses like cheatgrass from propagating throughout the fall and winter. The Rangers have been busy this summer preparing spray areas for fall management.

Summer mowing is part of the Rangers’ attempt to provide an integrated management approach to weed management. Noxious weeds have been known to develop a resistance to herbicides, and hardy perennial weeds easily survive “top kill” application due to their significant stores of energy below ground. Mowing reduces seed production and stimulates weeds like Canada thistle to “flush out.” This method encourages the plants to use more energy in creating more green foliage and also provides greater surface area for herbicide application. The mowed areas are less likely to survive the winter due to less stored energy, and the herbicide applied to the plant surface is quickly transported to the roots where it can do more damage to the plant.

Another part of the fall battle on weeds is cheatgrass control. Cheatgrass is an annual that has the ability to propagate throughout the fall and winter. Plateau is a herbicide that is used because of the soil residual that prevents cheatgrass from emerging. These treatments have proven very successful over the past two years.

The Ranger staff has been prioritizing fall spraying areas throughout the summer based on areas that were mowed, resident input and critical habitat areas. A target weed species list is generated by the Colorado Department of Agriculture, which lists the most noxious weeds in the state, and under state mandate requires property owners to control these weeds. The amount of control is dependent on each species, with the goal of a reduction in numbers over time.

The Ranger staff encourages residents near Open Space to monitor and manage weeds on their own properties and in the Open Space by their homes. Residents are allowed to mow a four-foot buffer in Open Space, which can help in weed control. A resident can also use a broadleaf specific herbicide like Weed Be Gone, but residents should never use herbicides like Round-Up because it kills all plants in the management area.

Before treating weeds in Open Space, the Ranger staff asks that you contact our office and schedule a field visit so that we can evaluate the weed problem and make recommendations. Dumping materials like grass clippings in the Open Space is prohibited and can suppress desirable species and encourage weed growth. If you have any questions on fall weed management, please contact Gary Norton at 303-979-1876, ext. 170.

Ken-Caryl Ranch