The following  Questionnaire will assist you in determining what types of stewardship and recovery strategies relating to vegetation are the most applicable for your property.

Weeds are invasive non-native plants that displace native vegetation and can be detrimental to your property’s land uses (such as grazing, crops or open space). The Colorado Department of Agriculture (CDA) uses the specific term “noxious weed” for weeds deemed as threats to native ecosystems and agricultural lands. The CDA noxious weed program, as well as County weed control programs, are discussed in more detail in the ‘Noxious Weeds – State and County Regulations’ section of Chapter 3.

Before determining how to manage invasive weeds, the first step is being able to identify them on your property. The CDA provides a number of helpful resources for identifying noxious weeds. Their website provides a full list of the noxious weed species, as well as pictures, Fact Sheets and a mobile app for identification. They also have a list of contacts for all of the County Weed Programs within Colorado. Your County Weed Program manager is also a great resource for additional information about identifying noxious weeds on your property.

CDA Noxious Weed Resource

Colorado Noxious Weeds Mobile App

by State of Colorado

The following pages have Fact Sheets for three noxious weed species that you are likely to encounter in the Lefthand, Big Thompson, Little Thompson and St. Vrain watersheds. You may notice that each of the Fact Sheets include management recommendations, separated into Cultural, Biological, Mechanical and Chemical categories. These categories, as well as how to choose the most applicable one for you, is discussed on the ‘Invasive Weed Management’ strategy sheet

This is a non-native perennial plant that spreads by an aggressive creeping horizontal root system, as well as seeds. Several small purple flowers grow on top of the spiny plant. Canada thistle can blanket large swathes of streambanks and pastures with dense prickly patches. These patches can significantly reduce crops, livestock pasture land and native vegetation

In contrast to Canada thistle, Scotch thistle is a large biennial plant that only grows from seeds. Scotch thistle can grow extremely large, up to 12 feet tall, with spines all over the stems and leaves. Because this thistle forms large dense thickets of tall plants, they significantly decrease the quality of pasture lands and croplands, and replace native grasses and wildflowers.

This is a thorny tree (or shrub) with gray-green leaves and olive-like fruit. Russian olives reproduce by seeds or roots, and birds readily spread the seeds. Although once thought beneficial as a windbreak, this species forms dense clumps in riparian areas, displacing native trees and shrubs. Although used by some birds, riparian areas dominated by Russian olives have less bird species diversity than the same areas dominated by native trees and shrubs.

Other noxious weeds that are common along the northern Colorado front range include (click for fact sheets):

Common Teasel
Flowering rush
Diffuse Knapweed
Eurasian watermilfoil
Russian knapweed
Salt cedar/Tamarisk

In addition to noxious weeds, there are also less invasive weeds and plants that certain landowners simply may not like. The non-native crack willow tree (Salix fragilis) is not on the noxious weed list, but it is often considered a weed by many landowners. This species of willow tree grows along streams and is considered detrimental because it grows fast, forms wide patches that displace native cottonwoods and peachleaf willows. It often also creates large areas of shade that prevent native shrubs and grasses from growing. The tree earned its name of ‘crack willow’ because it is has weaker wood and branch angles that result in large branches and trunks breaking (or cracking) in storms. While these trees have their downfalls, a landowner may not want to remove them because this would create a treeless area. This bare area could then take decades to regrow into a healthy riparian woodland. If you do not want crack willows to be growing on your property, a better approach is to remove them when they are younger, smaller plants and replace them with desirable vegetation.