Gardening & Living in Grand Style
Controlling weeds before they start…
by Michael Johnson
Mar 06, 2014 | 2056 views | 0 0 comments | 4 4 recommendations | email to a friend | print
Russian thistle
Russian thistle
With the warming weather comes those plants that thrive as if by magic – yes, I’m talking about weeds. Few people I have met like weeds, although whether a plant is considered a weed often is truly in the eye of the beholder.

Usually the problem with a weed is that it is taking up space or using water that we need for other plants. Or the weed is not providing us with the visual eye-candy we want from our landscapes.

For many, the process of controlling weeds starts after the unwanted invaders are discovered. But you can take steps now and in the future to put a stop to weeds before they start. Here’s a cautionary tale, just so you know how quickly weeds can take hold: the often ever-present Russian thistle, or tumbleweed, needs just a little bit of moisture to germinate and insert a taproot, which it can do in a total of 12 hours.

A fairly common and easy way to limit weed growth is to use mulch. This is done by placing some type of material, hopefully organic, in a layer 2 to 3 inches thick around annual and perennial plants, shrubs and trees. This material creates a barrier to any seed germination. I say “hopefully organic” because I think wood mulch or some combination of groundup leaves and plant debris is better than rock or pebbles. However, either could work.

You could somewhat enhance the effectiveness of this mulch by placing a good woven, but not plastic, weed barrier that allows water to penetrate into the soil under the mulch. The downside to using a weed barrier is that dust and dirt will build up above it over time and eventually allow weed growth on top.

Another method is to out-compete the weeds, which can be done with lawns or mass plantings of annuals or perennials. The healthier your turf grass is, meaning no open spots and not cutting it too short, the better it will be at keeping weeds at bay.

Mass planting annuals, perennials and some types of vegetables so that they grow together and eliminate light reaching the underlying soil will also help keep weeds from germinating and growing. This assumes you provide your plants with adequate water and nutrients.

Still another method involves how much or little you disturb or loosen your soil. Many weeds need this disturbed type of soil to get a start. Russian thistle and kochia are two examples of weeds that can really take over such an area. So you can have some positive effect by not disturbing or working your soil. This would be useful for those who have larger areas they don’t actively manage. If you have such an area, it’s best if you only walk along paths, don’t drive vehicles over the area and don’t otherwise turn over or loosen the soil.

A somewhat last-ditch effort to stop weeds is through the use of a pre-emergent herbicide. Pre-emergent herbicides are applied to the ground before weeds emerge, creating a layer of chemicals that, when the seed germinates, kills it soon after germination. Usually, the pre-emergent is applied, watered in and then not disturbed. Corn gluten meal has been used as an organic pre-emergent control for weeds, but isn’t very effective when first used. It does seem to acquire more effectiveness with multiple seasons of use, but even then it’s not nearly as effective as commercial pre-emergents. A pre-emergent chemical for turf to stop various grassy weeds and some broadleaf weeds is pendimethalin, although benefin and dithiopyr can be used. Pre-emergent chemicals for shrub and flower beds include trifluralin, dithiopyr, isoxaben or oryzalin. Remember to always read and follow the labels on any pesticide you use, whether organic or non-organic.

Thought for the day: “Weeds are nature’s graffiti.” —Janice Maeditere

Have an idea you’d like Mike to consider writing about? Want more information about these topics? Call the Utah State University Extension Grand County office at 435-259-7558 or email Mike Johnson at

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