Open Space Weed Management

Open Space Weed Management

Rangers Weed MapSpring is here and along with warmer temperatures and longer days, weeds are starting to appear in lawns, parks and open space areas. As part of an integrated management approach, herbicides are used to combat weed infestations in the open space. This year’s herbicide applications will be conducted from approximately April to July depending on weather and growing conditions.

Bare ground areas like picnic pads, hard surface trails and kiosk pads are treated first with a pre-emergent herbicide. Applications can be conducted before weeds emerge and these herbicides prevent weeds from germinating in the area throughout the growing season.

The next weeds to manage are the biennial weed species like musk thistle and knapweed. Knapweed and musk thistle are list B noxious weed species, which mandate that landowners make attempts to control and stop the spread of these weed species. The first year and early spring growth form for these weeds is a rosette of basal leaves lying close to the ground. At this stage they are most vulnerable to chemical application because of their increased uptake of water and nutrients. Even though knapweed and musk thistle can be effectively treated all the way up to the budding stages, we have found that spring and fall spraying in the rosette stage is most effective.

As spring turns into summer, the Ranger staff turns their attention to deeply rooted perennial weeds like Canada thistle. Spraying Canada thistle and other deeply rooted perennials is more effective when the plants have bolted and grown to approximately 10 inches in height. At this point, they are still transporting nutrients to the root system, which will allow for more herbicide uptake.

The weeds being managed this season are very aggressive invaders that have the potential to take over native plant communities. Priority was given to areas where infestations pose the worst threat to native plant communities and where they are bordering home lots. A contract herbicide applicator and the in-house open space maintenance crew will be performing the herbicide applications. Contact the Rangers with any questions about noxious weed management or specific weed management areas at 303-979-1876, ext.170.


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Ken-Caryl Ranch