By Ben Bain
La Plata County Weed Control Coordinator
Although we are in exceptional drought, the weeds don’t care. Nonnative plants that come from other places in the world are remarkably good at taking over our local ecosystems and thus limiting biodiversity.
These foreign plants do so well because there are few species that will feed on them, making them more likely to proliferate. As we roll through the driest month of the year, it is still important keep an eye out for these invaders before it is too late.
The first step is to be able to correctly identify plants on your property. It’s tricky because many will be natives. There are good identification resources online, such as La Plata County’s site, laplataweeds.org. If you still can’t find out what you have on your own, you can bring samples to the Colorado State University Extension Office or email pictures to me.
Once you have identified certain nonnatives, determine if it is an annual, biennial (two year) or perennial. This is very import because each type has a very specific life cycle. In general, annual and biennials reproduce only by seed. Eliminate the plant before it goes to seed and it won’t come back. Usually, it takes five to 10 years for the seed bank in the ground to be depleted, but it does get much better over time.
However, if you’re dealing with perennials, it gets more complicated, as some of these plants have an underground creeping root system that goes 10 or more feet down. No matter how many times you cut it, the root system is still alive. A broad-leaf selective herbicide is usually the best option to control these types of plants.
This type of herbicide will target only broad-leaf plants and will not harm nearby competitive grasses. Always use an herbicide that is systemic (meaning it will translocate into the root system) when spraying perennials because common formulas like 2,4-D will not work. Mix in a non-ionic surfactant when spraying herbicide because it breaks up water surface tension and helps spread the formula better.
In general, you want to spray, dig up or mow annuals before they flower – typically, in late May or early June. With biennials, you want to treat before flowering, which can be done when the plant is in its first-year rosette stage and/or flowering. Once these plants flower, seeding occurs soon after, and the plant is done with its life cycle.
Perennials can be treated in late spring during the “pre-bud” stage. But for the most effective time, wait until the first fall frost. This is when the plant is moving all available nutrients downward into the root system. Once you have eliminated your weeds, you will need to fill in the blank spots with some kind of other vegetation, otherwise they come back.
If you’re not up for spraying yourself, you can hire someone to do it but be aware most applicators are very busy this time of year, so book ahead. The weeds office provides free land consultations to all landowners/managers in the county. The cost-share program is available to assist landowners with deferring the cost of herbicides and also seed.
For more information, visit laplataweeds.org.
Ben Bain is the weed control coordinator for La Plata County and is located at the Extension Office at the La Plata County Fairgrounds. Reach him at firstname.lastname@example.org or 382-6470.