Spring Weed Control

Bulletin #TP1004

Horticultural Observations for Healthier Landscapes

There are different ways to deal with weeds in the lawn and landscape. Trying to ignore them is not a good idea. They soon will get out of control, and takeover.
To prevent a "hostile takeover", start controlling them as soon as the weather starts geting sunny. By applying a "pre-emergent" herbicide (most areas in February) throughout your lawn - this will prevent newly blown-in weed seeds from germanating and sprouting. With a bit of luck, and routine application you may never even see a weed invasion this year.

If you missed the chance to prevent the weeds, spring is the time to address the issue and begin control, in order to minimize the seeds these weeds will ultimately produce (if they are not killed before going to seed.)

Here are a few things you can do about your spring weeds:

◊ Understanding Pre-emergent Herbicides

◊ Understanding Post-emergent Herbicides

◊ Selective Post-emergent Herbicide

◊ Broad Spectrum Post-emergent Herbicide

Understanding Pre-emergent Herbicides

If the temperatures are not too high yet (90+F), then it's not too late to begin pre-emergent treatment on your lawn. These products do put some added stress on your grass, so applying during summer stress is generally not advisable.

(image above is "Spurge")
During a colder winter January may be a bit early, but we often have very little frost, so watch out for those pesky seeds sprouting up.

The little seeds that continually blow into your yard are your biggest enemy for weed control.

These products come in a variety of brands. Most are effective against broad leafed and grassy weed seeds. Always read the label carefully, some can damage cool season grasses.

If applied properly, pre-emergents do not kill living plants! They simply prevent seeds from sprouting. Virtually any seeds; so if you are planning to over-seed you lawn, you'll need to wait 3 to 6 months before over-seeding after application of a pre-emergent.
Good times for applying pre-emergents (in most southwest desert areas) are early February, May and late October.
(top)

Understanding Post-emergent Herbicides

To understand the difference between broadleaf weeds like dandelions, spurge, oxalis and chickweed, and grassy weeds like crabgrass, foxtails and goose grass; Broadleaf plants have wide leaves - grasses are very narrow. A broadleaf weed reacts the same as a diserable Rose would - so use care when applying.
Broadleaf weed killers don't kill grasses, and "Grass Only" killers don't kill broadleaf weeds. Read the label carefully - some products labeled grass killers also kill broadleaf. Until you are confident with an herbicide - do not depend on the large print. Read the details.

Foliar post-emergent herbicides are absorbed through the weed's leaves and kill the entire plant, roots and all. Most are designed to decompose once in the soil, but some can translocate in the soil and attack nearby plants. Read the label details.
If used according to directions and applied at the correct rate, it most often won't hurt desirable shrubs and trees as long as it doesn't get on the leaves. However, if a non-selective or broadleaf weedkiller gets directly onto the roots of a broadleafed plant (like a rose, etc.) it will damage or kill it. Be care with herbicides!

Avoid using post-emergents when it is windy. They can easily travel to desirable plants.

Take a little time and be sure to get the right products for the right pests! The product label is a good place to start...

Do not use herbicides indiscriminately as the unnecessary broadcasting of chemicals is bad for the environment and a waste of hard earned dollars! Make your product choice count. When looking for advice, try looking at websites that are not selling you a product that their advice specifies. This conflict of interest, sets the stage for much of the poor advice found in stores or on the internet.
Controlling weeds can sometimes be vary challenging and complex problem. The best solution might be one that can not be anticipated within the scope of this article.

(top)

Selective Post-emergent Herbicide

Controlling Grassy weeds. For shrub beds and tree wells, identify your weeds first. If you have grassy looking weeds, like bermudagrass, annual bluegrass (poanna) and crabgrass in your flowerbeds and ground covers, the use of a product like Orthos’ Grass-B-Gon has good reviews. Don't expect control too fast. A couple applications and a couple weeks are usually needed before you'll see the grassy weeds die-back.

Controlling Broadleaf weeds. If these are infesting your lawn, you'll want a post-emergent broadleaf herbicide. Remember! Broadleaf weed killers kill Roses and Hibiscus too - use caution.

For small, isolated broad leafed weed problems in lawns, spot spray with a liquid broad leafed weed killers (2-4-D is a common broadleaf herbicie)

It is common for mist from the application of broadleaf herbicide to travel to the leaves of desirable broad leafed plants and damage or kill them if you use a
If you can be more specific with the type of herbicide used, you can reduce the chance of plant injury considerably.

Broad Spectrum Post-emergent Herbicide

In rock landscapes, you may want to just kill everything. But please be careful! Often there are roots of desirable plants that have traveled into your rocked area. Many herbicides can penetrate the soil, especially if applied too heavily. Read the labeling and use caution when applying.
Broad spectrum foliar herbicides like Glyphosate are useful here, just be careful when applying. Avoid spraying onto the exposed or surface roots of desirable plants nearby.
(top)