Pre-emergent Control

February 6, 2016

I have never seen this addressed so I'm seeking information on the subject of pre-emergent herbicides. How is it used and where is it available?

Pre-emergent herbicides are weed preventers.  They should help suppress annual weeds from germinating.  Since we have two seasons of weeds—winter weeds and summer weeds, they can be applied in the fall to prevent winter weeds from germinating and then in late winter/early spring to prevent the summer weeds from germinating. Again, they only work for annual weeds, not perennial weeds like nutgrass, dandelions, etc.  An annual is a plant that germinates, grows, sets seeds and dies in one season.  Pre-emergent herbicides are often sold at nurseries and garden centers in the fall and early winter.  I only recommend them for use in well-established lawns.  While there are some formulations for flower beds and vegetable gardens, I want some of my plants to reseed themselves, so I don’t use any herbicides in these gardens—just a good hoe and mulch.  For lawns, they often sell what is known as a weed and feed.  Right now if you are using it, you would be fertilizing winter weeds, since the lawn is still dormant. I prefer using a stand-alone pre-emergent, not one mixed with fertilizer.

November 7, 2015

I have cleared brush-honeysuckle vines, briers, little trees etc. Today, I am beginning to plant 1200 bulbs in this area. I am wondering, after the bulbs are all planted, is there some kind of pre-emerge that I can apply so the vines and briers will not come back with a vengeance?

Unfortunately, most of the weeds you are describing are perennials or woody plants which a pre-emergent has no effect on.  Pre-emergent herbicides only work on annual weeds—those that germinate, grow and then die in one season.  The herbicide prevents the weed seeds from germinating.  It will not prevent the roots of perennials from growing, so just be vigilant, mulch and keep it as clean as you can.  Once the bulbs have had at least 6 weeks growing time following bloom, then the bulb foliage can be mowed down and the weeds too. 

September 2012

For years my wife's father had his yard in primo condition. Since his passing, the yard has cultivated a dandy crop of crab grass and other weeds unknown to me. I have used Ortho Weed Killer with crabgrass preventer, and it really doesn't seem to be doing the job. In thinking ahead to spring of 2013, what would be my best option in eradicating crabgrass from the yard, and should I start this fall. I do plan to apply a Wintertime weed and feed probably in mid October.

 I don’t like to use any fertilizer on lawns in Arkansas after mid September unless you are growing tall fescue. Most southern lawns go dormant for the winter, and I would hate to encourage new growth, too late in the year, or spur on winter weeds. Crabgrass is a summer annual weed, which means it germinates in late spring, grows all summer, sets seeds and dies in the fall or early winter. There is nothing to do this fall to prevent it for next year. Apply a pre-emergent herbicide in late February and a second application in early April and you should be good. Monitor for weeds during the growing season. The more dense the lawn grass, the less weeds you have. We do have lawn care calendars for each of the lawn grasses grown in Arkansas on our website:

Lawn Care Calendar: Bermudagrass

Lawn Care Calendar: Centipedegrass

Lawn Care Calendar: St. Augustinegrass

Lawn Care Calendar: Tall Fescue

Lawn Care Calendar: Zoysiagrass

November/December

I missed the chance to apply a pre-emergent herbicide this October to kill spurweed. Are there any 2.4-D combination products that are safe to use on Centipede grass? I've got Centipede and Bermuda in the problem area. If so, I understand you use it December thru March, at a time when temperatures exceed 55 degrees. Do you agree?

 Spurweed ( Soliva pterosperma), also called lawn burweed, stickerweed, and sandbur has become quite a nuisance in many lawns and I am happy you are preparing to kill it way before bloom time and then seed (sticker) set. There are numerous formulations of two and three-way mixes of 2,4-D, dicamba and MCPP. Make sure you read the label before purchasing that they are safe for southern grasses. Many will give reduced rates of application for Centipede and St. Augustine. You do want a fairly, calm sunny day with temperatures above 55 for best application and control. Spray once and then monitor your weed population and you may need to reapply two weeks later.

April 2010

I live in west Little Rock on a very secluded lot with lots of trees and a small stream in the front. My beds are a mess! There are weeds everywhere and they continue to come back no matter how many times I pull them or spray them with Round Up. I have tried a pre-emergent, to no avail. The shrubs are overgrown and I have WAY too many trees just growing on top of each other. I need help along with information and education. Where do I start? A landscape architect? A nursery? A tree/lawn service? I am so overwhelmed that I am paralyzed! I am hosting an outdoor wedding party on June 19 and I break out in a cold sweat every time I think about it, which is hard to do considering I am in a constant state of hot flashes! I would GREATLY appreciate any advice you could give me or any names you would recommend that I contact. My lot is a little over an acre and what seemed like the perfect situation at the time we bought the property, but has doubled the trouble, we also own the lot next door that is empty except
for TREES!

 I can’t make specific suggestions on who to hire, but there are many qualified landscaping folks out there who could come and help get your yard in order. I would start with some of your local nurseries and ask them who they recommend to do work. Ask for references and see some of the work they have done and then choose. From the pictures you sent, it doesn't look that bad—just very natural. A good layer of mulch will go a long way in helping to keep weeds down. Pre-emergent products only work on annual weeds, not perennials, and from the looks of things, that seems to be more your problem. I saw poison ivy and Virginia creeper in several of the shots you sent. Regardless of what you do this year, more weeds will follow, that is the nature of the beast. A good layer of mulch and a few rounds with the hoe or herbicide will help annually. To make your life easier, concentrate your efforts for now on where the wedding party will be and don’t try to tackle the entire yard at once. Bring in some beautiful containers and judiciously spread them out and your party will be a success!

February 2010

 My lawn is part St. Augustine and part Bermuda grass. What is the best pre-emergence to use and what is the best fertilizer that works with both types of grass?

 The main reason to apply pre-emergent herbicides for warm season grasses by March 1 is the prevention of crabgrass. Products containing benefin, pendimethalin, or bensulide are all effective. There are numerous product names, but they usually always have crabgrass or weed prevention on the label. All too often we run into weed and feed formulations. If possible, go with a stand-alone herbicide, since Bermuda and St. Augustine will not benefit from a fertilizer application until April, so the fertilizer is more a waste or a boon to your winter weeds. As to fertility, both grasses need a slow release high nitrogen fertilizer since nitrogen is the nutrient used the most by lawns. Look for something with a higher first number and the next two smaller such as 27-3-4.  Fertilize both grasses once they are totally green. St. Augustine could be happy with one or possibly two applications of fertilizer, while Bermuda grass will respond well to multiple applications, depending on how often you want to mow.

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