The barren landscape is springing back to life after its winter respite and our energy levels seem to match. We feel we have to do something: ”Boy, this is the year I need to tackle the . . .” Fill in the blank.
If you fill in that blank with ”weeds, crabgrass, creeping Charley,
(etc.),” you have either booked yourself into many hours on your knees or you will be applying some chemical means to control those plants that you have decreed are out of bounds in your yard.
The garden centers are armed to the teeth to help you in these chores, but you`ll have to search to find the kneepads. Front and center will be stacks of huge bags containing every combination of product for the lawn:
fertilizer plus crabgrass preventative; starter fertilizer for new lawns plus crabgrass preventative; fertilizer plus broadleaf weed control; fertilizer plus insecticide; and on and on.
If you plan to do battle with weeds, one fundamental decision needs to be made: to use or not use chemicals. For every study that is released saying the active ingredient 2,4-D causes cancer in certain animals (including humans) under certain conditions, there are years of scientific testing done by the manufacturers that conclude it is a perfectly safe product when used according to directions. For every study showing groundwater being
contaminated by pesticides is a study showing how effective a lawn is in absorbing chemicals and how little is washed away. For every study showing that toxins remain in the soil far longer than manufacturers contend are the rebuttals about how quickly the products break down and disappear with no residual effects to the environment.
The organic route
If you are (or aspire to become) an organic gardener, a weed-free yard may involve more work and better cultural practices, especially on your lawn. Grass will outcompete weeds if its needs are consistently met. Flowers and vegetables can be mulched to suppress weed seeds from sprouting. Also, organic gardeners as a whole are a bit more tolerant of weeds, recognizing the diversity within the plant world.
”We recommend that people not use herbicides when they`re not needed and if they are needed, to spot treat,” said Jim Schuster, senior
horticultural adviser with the University of Illinois Cooperative Extension Service. ”You need to properly identify the weed, determine the proper time to kill it and use the right product.
”If you do it right, one application a year will knock them down pretty well. If you use a single herbicide, you may have to use it spring and fall for several years to control tough weeds.”
Whether you decide to use them or not, here`s a primer on what`s available. Weeds are most susceptible to chemicals when they are young and actively growing, as in the spring we are about to experience.
The safest killers
The safest weed killers are known as contact herbicides, which burn the foliage of the plant they hit but do not kill the roots. You can make your own from a liquid fertilizer of a 20-0-0 formulation sprayed directly on the plant, for instance. Household detergents can kill grass and so can alcohol.
Ringer Corp.`s SharpShooter weed killer is made from potassium salts of fatty acids, has no residual effect on the environment but may have to be used several times on weeds that regenerate from their roots. It kills anything it hits but works best on young weeds, said Rob Ringer.
Weed killers that move through the plant`s system to kill out the roots as well as the foliage are known as systemic herbicides. Most chemical weed killers fall into this category.
From there, we move to the big three: the crabgrass eliminators, which fall into pre-emergent and post-emergent formulations, meaning they either prevent the seeds from germinating or kill the seedlings shortly after germination; the selective herbicides that kill weeds but do not affect grass; and the non-selective herbicides that kill any green material they touch.
Pre- and post-emergents
If you had crabgrass last year, chances are good it will return. It is an annual plant that must resprout from seeds in the ground. It also needs light to germinate, so if your lawn is cut too short or is not terribly lush, there`s a good chance crabgrass and its ilk (goose grass and fox grass) will find and fill the open spots. Applying a pre-emergent herbicide will prevent annual weeds from sprouting and taking hold.
Timing is important: Soil temperatures of 55 to 59 degrees are needed to germinate the seeds. Two other ways to remember the timing: when forsythias bloom and before when the first crop of dandelions go to seed. Scott`s formulation uses Pendimethalin, which forms a gaseous barrier that knocks out emerging seedlings. Others use Trifluralin, which surpresses germination.
To start a lawn this spring or overseed an established lawn, a so-called ”smart” herbicide called Siduron made by Du Pont allows cool-season grass to germinate but not weeds or warm-season weedy grasses. This is normally found in bags of fertilizer formulated for newly seeded lawns and which have a higher phosphorus content for root development. These products are usually higher in price as well.
If you want the herbicide without the fertilizer, Greenview has a product called Preen, which uses Trifluralin, while Scott`s Flower and Garden Weed preventer is made with Dacthal. Neither product should be used on lawns and although both say they can be used in vegetable gardens, most experts strongly advise not to use herbicides among food crops.
Selective herbicides
Next to those products at the garden center will undoubtedly be the bags with some variation of the ”weed and feed” tagline. These contain fertilizer plus selective herbicides that knock out weeds like dandelions while leaving the grass alone. They are not effective on crabgrass or its cousins.
Both Scott`s and Greenview have a regular formulation and a ”pro”
line. Careful scrutiny of the labels will divulge that both regular formulations contain 2,4-D and MCPP, while the ”pro” lines add Dicamba to those ingredients.
Why three toxins? Isn`t that more lethal than if only one were used?
Schuster, of the extension service, said the combination is necessary to control tough weeds such as ground ivy, usually referred to as creeping Charlie. ”It`s not necessarily more toxic,” he said, because each chemical is used in lesser doses than if just one were in the mix.
Greenview General Manager Gene Wright said the company`s 2-Way Green Power will control ground ivy but it may take more than one application, especially if the plant is established. With GreenPro, Wright cautions that if the product is overused, the dicamba can damage shallow-rooted trees.
Overuse is always a concern with herbicides. Many weeds are classified hard to control with any chemical means, which can lead homeowners to use a stronger dose than stated on the label. ”In terms of misuse, yes, we fear it,” Schuster said. ”When you try to take out a weed that is very resistant to most herbicides, people add more, which usually doesn`t kill more weeds, it damages more desirable trees and shrubs.”
Schuster said that most of the active ingredients in 2,4-D and MCPP break down within two week, dicamba in about a month. He said grass clippings can be composted and by the end of the cycle, no herbicidal residues will remain. Those clippings should not be used as mulch for at least six weeks after being cut as an extra margin of safety to allow the herbicides to break down, he said.
Directions advise to apply the granular formulations while the grass is damp and not to water the material in until it has a chance to work on the foliage of the weeds-usually 24 hours. During that time, it is important to keep all humans and especially pets off the treated lawn. When watering, Schuster said, at least a half inch of water should be applied to make sure all the granules are dissolved and off the grass blades. The lawn should be dry before foot traffic is allowed.
Liquid formulations of herbicides can be used for spot treating small areas where the weeds are most active. Treated areas should be off limits to foot traffic until the grass dries. When trying to tackle ground ivy or similar difficult weeds, the trio of herbicides mentioned earlier are available in several formulations using the generic name Trimec.
The down side of spraying is spray drift, which may damage nearby plants. Gnarled leaves on lilac bushes are a giveaway that 2,4-D has been sprayed somewhere in the general vicinity. On hot and windy days, sprays tend to volatilize, sometimes sending their effects two or three houses away.
Non-selective herbicides
One of the surest ways to knock out tough weeds such as ground ivy and violets is to kill all the vegetation in a given area using herbicides that don`t discriminate and are therefore known as non-selective.
Glyphosate is the active ingredient that is the standard in this class because it breaks down rapidly. It is sold under the brand names Roundup and Kleenup. It works systemically, killing the plant roots and all within 10 days. Because the plants look fairly normal most of that time, users complained they didn`t look dead, so Ortho`s Kleenup brand boasts of a ”new fast acting formula,” which means they added another ingredient to make the plants turn brown shortly after they are treated.
Two weeks after application, the affected area can be worked up and replanted.
Other non-selective herbicides are more persistent, meaning they keep weeds from returning as quickly. ”They work fine as long as the product doesn`t move, but if it rains, it moves along with the runoff,” said Schuster of the Ortho product Triox, whose active ingredient is Prometon. ”I am not in favor of using it too often; I would prefer Glyphosate.”
Chemical companies have come under fire for showing their products being blithely sprayed by models in summery clothing. Extension officials say proper clothing should be worn when applying any chemical, including non-porous shoes, socks, long pants, long-sleeved tops and, preferably, a hat, goggles and mouth-nose protection to avoid inhalation of fumes. Rubber boots that can be hosed off are the ultimate if you are walking behind a drop spreader applying a granular herbicide.
Jim Fizzell, former extension adviser for Cook County, points to a commercial for Roundup showing how easy the product is to use and compares it to one of his experiences with the product.
”You see people on TV spraying weeds but you don`t see that you can get drift and it takes very little to kill grass,” he says. ”You have to be careful how you apply it and put a buffer of plywood or cardboard around the area you`re spraying to protect plants you want to keep.
”I was called in to treat poison ivy at a friend`s house. I used Roundup and killed the poison ivy all right, but it killed off everything in a 10-foot diameter from each plant. It really did a number on that grass.”
