Native versus introduced plant species


By Ethan Proud | PREVIEW Columnist

When it comes down to plants and invasion biology, there are really two categories: native and introduced. 

Native can be divided into beneficial, nuisances and undesirable depending on land type, while introduced can be divided into beneficial, invasive and noxious. 

Beneficial is the easiest category to describe and it covers plants that do not reproduce or compete aggressively, do not escape ornamentation (or have a limited spread), or plants that are useful for humans and livestock. Next time you go to the grocery store, look up how much of your produce is produced locally or imported and then look up the native range of the local produce.

Invasive and noxious plants versus weeds is where the classification gets interesting both environmentally and legally. Both invasive and noxious weeds have similar traits that make them weedy. Weeds, beyond the definition of a plant out of place, readily invade disturbed or degraded plant communities, have multiple modes of reproduction, high seed production, aggressive spread and seed longevity. This can also pertain to native plants that are undesirable or nuisances, but invasive and noxious weeds cannot be native. Climate shift in Colorado is not going to result in a native Colorado plant species being declared noxious if its range expands due to changing conditions.

An example of an invasive weed in Colorado that is not designated noxious is yellow sweetclover. Yellow sweetclover in certain years can be seen lining the highways and roads, yet in other years it is hardly noticeable. In can invade areas and can cause bloating or anticoagulation in livestock. It is also a popular plant for honey producers. Yellow clover also used to be prevalent in many revegetation mixes as it readily establishes and can help prevent soil erosion. 

So, what prevents all invasive species from being declared noxious? The Colorado Department of Agriculture maintains the Colorado Noxious Weed List, while individual counties have the right to elevate certain species through their integrated vegetation management plans. Noxious species cause economic, agricultural and ecological harm and are judged based on scientific metrics and listing assessments. Another criteria on which to base listing decisions is the feasibility of management goals. 

The state list divides species into A, B and C lists. A-list species are rarer and pose a major threat if unmanaged and the goal is total eradication. B species are widespread and their containment and eradication of satellite populations is the current goal. C-list species are so widespread that management is determined on the local level with priorities being suppression and education. 

A widespread species in Archuleta County like musk thistle is not likely to be eradicated on a countywide basis, but it is possible on individual properties or sites. Species that are uncommon like myrtle spurge, black henbane and perennial pepperweed are possible to eradicate with the proper amount of cooperation between agencies and private landowners.

Archuleta County Weed and Pest is your local resource for managing noxious weed populations and controlling other pests.

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