Noxious Weeds
Submitted by Jan Behler, CP Garden Club,
Master Gardener
What are noxious weeds? Noxious weeds are aggressive plants that are not native to our area. Most have come from Europe or Asia. There are many reasons for the classification “noxious weeds” but primarily it refers to their ability to spread rapidly and compete with native species. These weeds destroy and displace native plant species. Noxious weeds have an advantage because the insects and diseases that control them are not found here.
Colorado law has mandated to preserve our natural habitat and protect our native plant species that all weeds listed on the “A” list are undesirable and need to be eradicated. A partial “A” list of weeds would include purple loosestrife, orange hawkweed, yellow starthistle, myrtle spurge, dyers woad, cypress spurge, tansy ragwort, and medusahead. Of particular concern in Douglas County is diffuse knapweed because it seems to thrive in this environment and a single plant may produce 55-1500 seeds!
Noxious weeds are found more often in small acreage land, pasture, places where the soil has recently been disturbed (possibly new construction) than in the average homeowner”s lot. If you do find a suspicious weed on your property two good websites can help you with weed identifications. Douglas County information can be accessed at www.douglas.co.us then search noxious weeds or Douglas County CSU extension at www.colostate.edu (Natural Resources).
There are four types of control methods: cultural, mechanical, biological, and chemical. A good management system will usually use two or more of these methods.
- Cultural- The best way to control weeds is prevention. If you have healthy grass and plant vegetation on your property then weeds cannot get a foothold as easily. The most important prevention measure is to always keep weeds from going to seed, so that new infestations are prevented.
- Mechanical- The old- fashioned method of pulling and hoeing.
- Biological- The introduction of host specific predators from the weed’s native country( example: in Douglas county the brown-legged leafy spurge flea beetle has been used on an experimental basis to control leafy spurge.
- Chemical- The use of herbicides(2-4D, Roundup) Always read and follow label directions with applying herbicides. Spring is a great time to eradicate the weed while it is still small and just developing.
Hopefully, by being observant of your land and the surrounding area you can help preserve our beautiful natural environment from unwanted intrusion of non-native weeds that negatively impact our environment.