A PreEmergent lawn care product eliminates weeds at the earliest stage of growth — before you even see them. Several key factors are important to consider if you want to use this type of weed killer effectively.
Have you hesitated to use a preemergent herbicide because you didn’t understand what it does or how to apply it? Did you try one and have poor results?
This article will explain the concept of weed prevention: the benefits, the drawbacks, plus when and how to apply it. Learn to avoid the mistakes that lead to disappointment and more work!
A separate concluding article will assist you in selecting the best type of PreEmergent for any situation, including lawns, landscaped garden areas, vegetable gardens and non-vegetation areas.
Have you spent countless hours pulling weeds by hand, or repetitively spraying weed killers? We all hope for a better way to improve the appearance of our lawns. Welcome the PreEmergents: a group of garden products that offer a respite from that aggravating problem. No, they do not offer automatic salvation as in ‘use once and forget about it’. But they are one of the most important weapons in a gardener’s arsenal.
Typical applications occur in early spring before warm season weeds appear and in autumn for cool season weeds. These preventative herbicides actually can be helpful throughout the majority of the growing season. Various weeds germinate at different times, so repeated applications of the correct chemical can eliminate the majority of the weeds in any lawn or yard. Note these benefits:
Many folks just want to get the product down and get on with life. Do it when you think about it, is that o.k.? As long as you are early enough, as mentioned before, there is no harm in getting the pre emergent down way ahead of time. It just might wear out too soon to get the later batch of weeds if you start too early.
So if you realize that your yard conditions will likely require a second application anyways, just get it down and breathe easier. But what if you are late? Investigate the concerns about timing at this article When To Apply Crabgrass Preventer. Much of the information will apply to broadleaf weeds as well as the crabgrass concern that is emphasized. (It’s never over, if you don’t give up!)
The gardener who wants to know specifically when to apply a preemergent is going to have to do a bit of research. The temperature of the soil as it starts to warm up in the spring is going to be the primary indicator of the pending arrival of various weed species. You can be prepared for that by checking with the resources available in most states through your State University Extension program or through your County Farm Agent. (Yes, even if you live in the city, like San Diego for example, there is a wealth of helpful information from the farmer’s friend!) They will typically have charts or articles written up that offer the expected emergence date for common weeds in your area.
You can be fairly accurate by using an inexpensive soil thermometer. Testing should be done in moist but not soggy soil. First, poke a hole with a stiff rod to avoid damage to the probe, but not too big, as the soil must be tight against the probe. Notice the differences in various locations that are sunnier, dryer, or more exposed.
A fall or winter application is necessary in some geographical areas. Locations that deal with annual bluegrass or annual ryegrass will want to get their lawn covered prior to the initial seasonal autumn/winter rains. In some southern climates, a winter application is necessary to protect against crabgrass as early as January or February. A summer application can be helpful, even necessary, in those areas where certain weeds wait for the hot weather. Many spots need to be ready for a second onslaught by some early weeds that can reseed and grow the same season, like the ever-present dandelion.
Granular products are the most common type found in everyone’s local garden department. (In my opinion, it is unfortunate that they are usually combined with fertilizer. It is better to specialize when working on an issue of this nature.) These can be spread by hand just as you would throw out chicken feed. (Well, maybe you’ve seen them do it in a movie!)
A hand-held spreader works great to cover a medium sized area, as it throws out the product quite evenly as you turn the crank. For extremely large lawns, a push-type lawn spreader is best, the same type that many people have for applying fertilizer. Most products will specify on the label or have on-line instructions for what the setting should be on different units. Be aware that the cranking speed and walking speed will greatly affect the rate of dispersal and the distance the granules are thrown by a “broadcast” type spreader.
Only a drop-type spreader confines the preemergent to a well-defined area. Broadcast type spreaders can fling out an herbicide in a dangerous manner, getting into areas where you don’t want or don’t need the protection.
Safety Tip: If you find yourself dealing with this as a likely issue, and need to keep it out of a flower bed where you want to plant seeds or annuals, have someone walk along with you and hold a large sheet of cardboard or heavy tarp that can deflect the granules so they spread into the desired area only.
If you have a relatively small area that needs to be treated, especially just a few bare spots here and there, some manufacturers of lawn and garden products offer a shaker can or shaker bag that is quite handy. You may be able to create one from a coffee can, by drilling properly sized holes in the top.
APPLICATION: In all cases, the intent is NOT to cover the ground completely. You just want an even, consistent dispersal. In a square inch, you might only need a couple of granules, since typical application rates allow 1 pound to cover from 200 − 500 square feet. (Before you start: Read the Label Again! Calculate how large is your area! Plan your approach!)
Some brands offer a Liquid Preemergent in either a ready-to-use-spray bottle that attaches to your hose, or a concentrate to mix in your own tank sprayer. These are very convenient — a very quick way to apply the product to a large area. They are often more economical as well.
Be especially cautious, however, if the lawn area that you spray abuts any location where you will be planting soon. And even though it is liquid, it will not work if it remains on the grass blades.
Whichever method you select, it is imperative that you water the product adequately to get it into the top soil layer. This does not have to be done immediately, but within the time indicated on the label, usually 1-3 days. Waiting too long exposes the chemical to light and/or heat that will diminish its potency.
You can irrigate the lawn area, or allow rain to water it in, as long as it will be a sufficient amount. In most cases, you need not worry about using too much water. The exception is with the organic corn gluten pre-emergent which can get over-diluted, unlike the chemical products.
A lot to consider, right? Already this is a long article. Let’s evaluate this important concern on another page. I’ll get that posted as quickly as possible.
With Pre Emergent Down, Can I Plant Grass Seed or Sod? Questions & Answers to explain 4 different situations affected by this.
Learn When To Apply Crabgrass Preventer for the exceptions everyone loves to hear.
Can you apply Preemergent for Crabgrass in Bermuda when the lawn is dormant?
My Garden Needs: Crabgrass Preventer See a variety of products listed in the Garden Counselor Store.