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Deb Babcock

Deb Babcock's gardening column appears Mondays in Steamboat Today.

In the war against Whitetop (Lepidium draba), Routt County is fighting an uphill battle. This non-native creeping perennial mustard plant displaces our native plant communities, disrupts wildlife habitat and is toxic to grazing cattle.

In Routt County, we've noted an estimated 10,000 acres of this noxious weed growing in fields, roadside ditches, meadows and other open areas. Brought in from Europe accidentally in a shipment of contaminated alfalfa seed, this weed especially enjoys our alkaline soil here in Colorado. It is rumored to have arrived in Steamboat on a load of hay from Vernal, Utah. In the absence of competing plants, one Whitetop plant can spread as far as 12 square feet and produce up to 450 new shoots in a year.

It's one of the earliest noxious weeds to bloom in the spring, producing its flowers in April and May. The plant often is mistaken for the harmless field pennycress with its small white flowers in compact flattop clusters. But you can tell the difference when you try to get rid of the plant by pulling it out of the ground. Pennycress will pull up easily because it has a shallow root system. Whitetop, on the other hand, has an extensive root system that spreads horizontally and vertically, with many shoots coming up erect from all along the root. It won't pull up easily because the tap root grows about 15 inches into the soil and the lateral roots are a foot long the first season and between 2 and 5 feet longer each season thereafter.

Diligent digging might control small infestations, but the entire root system must be obtained and will likely require repeat digging for two to four years after the weed has first emerged. Chemical control using herbicides such as Campaign, Escort or Telar is the most effective way to eradicate this weed and will require several applications because the seed can remain viable for as long as 40 years in the soil. Follow label instructions carefully because some chemicals work only on rosettes before the plant blooms and others, such as Glyphosate, work better on a mature plant. It's important to re-vegetate as soon as possible after eradication so this weed won't regenerate.

Researchers are working on ways to control Whitetop through the planting of competitive plant species and with insects, but they haven't identified a successful program.

If you suspect Whitetop is growing on your property and need advice on how to deal with this Class B noxious weed, please contact county extension agent CJ Mucklow at the Routt County Cooperative Extension Office at 879-0825.