Here in the southwest, September into October is typically warm and sunny with plenty of T-shirt weather days ahead.
This makes it difficult to know just when to quit managing noxious weeds for the current season and to take a well-deserved rest.
The life cycle of the target species matters, with annuals having already gone to seed, but perennials, biennials are and winter annuals gearing up for winter and herbicide applications from now until the first hard frost are effective.
Herbicides are best used when temperatures are warm and plants are actively metabolizing, this range is usually 40-85 degrees Fahrenheit. If fall temperatures are not expected to exceed 40 degrees, it’s best not to waste your time and money. After a hard frost, when temperatures drop below 28 degrees Fahrenheit for four hours, the growing season is over.
Some weeds may be more resistant to cold temperatures, but you may be wasting herbicide on a plant that is entering dormancy. Instead, spade out any rosettes of biennial species and seedlings of winter annuals. For any plant with blooms, you can clip the seed heads off and bag them to prevent seed dispersal.
Prior to season-ending temperatures and weather, some plants may be shutting down for the season already. It may be tempting to get out one more time and get a final treatment, but do a quick evaluation of the target species first. If more than 40 percent of a plant has begun to turn yellow, then the herbicide won’t be absorbed effectively. If this is the case, you can survey the area for new germination and seedlings that will likely stay green until the weather shifts in an attempt to build a strong enough root system to survive the winter.
You can also hang the hat up when you have reached your management goals; it doesn’t need to be total eradication. Noxious weed control is a marathon, not a sprint. If your goal was to treat half of your property this year or to prevent any plant from flowering and all that’s left are rosettes, then call it a day and move onto another project like reseeding and establishing native vegetation — or maybe wax your skis and hope for an early winter.
Archuleta County Weed and Pest is your local resource for managing noxious weed populations and controlling other pests.
Email list
Do you want to be added to our email distribution list to learn about upcoming programs and the latest resources? Email cindi.galabota@colostate.edu to be added to our list.
Or, to learn more about the many programs, resources and services offered by CSU Extension, visit https://extension.colostate.edu.
CPR and first aid classes
CPR and first aid certification classes are offered every other month at the CSU Extension building, generally on the third Monday and Wednesday from 6 to 10 p.m. The cost for the classes is $80 for combined CPR/first aid and $55 for CPR, first aid or recertification. Call the Extension office at (970) 264-5931 to register.
Check out the online option on our website, archuleta.extension.colostate.edu.
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