JoAnne Skelly: Getting ahead of the weeds

Weeds are taking off. Some are already blooming. Yesterday I saw my first bur buttercup, Ceratocephala testiculata, in bloom. While this tiny little winter annual with its petite yellow flower doesn’t seem like much at two inches tall, its Velcro-like seed heads wind themselves up in an animal’s hair and eventually have to be cut out.

Redstem filaree or cranesbill, Erodium cicutarium, another winter annual, that is also sometimes biennial, has been growing almost all winter. With its fernlike leaves and tiny purplish-pink flowers, it’s initially attractive until its spike-like seed head that looks like a crane’s bill, develops.

Weeds can be managed with a number of techniques. Spraying bur buttercup is futile. It will continue to go to seed as it dies. It comes out of the ground quite easily, so hoeing before plants go to seed is a good strategy to eliminate it. The best method to control redstem filaree is to remove it before it goes to seed. Herbicides are only marginally effective in controlling it.

Applying herbicides successfully requires some knowledge of how they work.

Herbicides can be pre or post-emergent, selective or non-selective. A pre-emergent herbicide is applied to the soil before a weed emerges. It prevents seeds from growing. This type does not work on existing weeds. A late fall application of a pre-emergent herbicide listing bur buttercup or redstem filaree on the label would have reduced current populations significantly. Applying a pre-emergent now will reduce spring and summer weeds. For example, it’s not too late to apply a pre-emergent control for the seeds of puncturevine, Tribulus terrestris.

For already-growing weeds or perennial weeds that come back each year, you need a post-emergent herbicide. Selective post-emergent weed killers, such as Weed-B-Gon and Grass-B-Gon, are designed to kill either broadleaf weeds such as dandelions or grasses. They don’t work on both types of plants. Beware, if you spray a broadleaf herbicide on your flowers or a grass killer on your lawn, these desirable plants will die too. Non-selective herbicides such as Roundup kill most plants indiscriminately, including your flowers, lawn, trees and shrubs.

It is critical to effective weed management to read the label and learn what kind of herbicide a product is. Before you spray, identify the weed. Not all herbicides work on all plants. Often there are alternatives to spraying. Contact your local Cooperative Extension office for help with weed identification.

The brand names were used with the understanding that no discrimination is intended and no endorsement by Cooperative Extension is implied.

JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension and may be reached at skellyj@unce.unr.edu or 887-2252.