Weed Control Before Seeding

Seed first or spray weeds? Early weed control is an important step in profitable canola production. Saskatchewan research on preseed weed control in wheat showed that early weed control was more If you have decided that you are ready for a total lawn makeover, your first order of business should be to get rid of the weeds. Most professional landscapers Preparing For Overseeding : Yardener.com

Seed first or spray weeds?

Early weed control is an important step in profitable canola production. Saskatchewan research on preseed weed control in wheat showed that early weed control was more important to yield than early seeding.

Pre-seed weed control will manage weeds that emerge ahead of seeding, reducing crop competition for light, moisture and nutrients.

Growers waiting to seed may find that fields too wet for the seeding unit may support the sprayer — although deep ruts are not great for the seedbed. High flotation tires on the sprayer will reduce rutting.

Cool, wet conditions that are holding up seeding can also reduce herbicide efficacy, but early weed control with lower efficacy is generally preferable to no control at all or late control with higher efficacy — as long as weeds are present and not frost damaged.

Clark Brenzil, provincial specialist, weed control, with the Saskatchewan Ministry of Agriculture, explains how cool, cloudy conditions affect herbicide efficacy:

In the case of herbicide applications following a nighttime frost or near-frost event, the herbicide activity on a cloudy cool day would be next to zero. Biological activity would have stopped during the night, and would not start up again until the plant warmed to at least 5°C — and even then it would be very slow. A few hours between 5°C and a daytime peak of 10°C would not be enough warmth to get plant metabolism going to a point where herbicide was all that effective, especially with the cloud. No biological activity = no herbicide activity. Ideally, you want a day or two of warm sunny days and night time lows of 4°C or higher before spraying. If applied more than 48 hour before the frost event, efficacy on living plants will be retained and the plant will continue to decline when it warms up again.

If faced with a decision to spray some fields and not others, be sure to spray Clearfield fields before seeding. Otherwise you have to wait until the two-leaf stage of the crop to spray.

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Controlling Weeds before You Plant Your Lawn

If you have decided that you are ready for a total lawn makeover, your first order of business should be to get rid of the weeds. Most professional landscapers will tell you that the best way to get rid of weeds is to spray the entire area with an herbicide.

The most commonly available, easiest to use, and relatively safest herbicide is one with the active ingredient glyphosate. Brand names include Roundup, Kleenup, and others. The best way to tell whether you’re getting the product you want is to ask your hardware store or garden center associate to help you. Be sure to read the label and look for the active ingredient glyphosate.

You will probably have to apply this herbicide more than once.

For a lawn over 1,000 square feet, you need to rent or buy a backpack sprayer to do the job. The herbicide comes in a concentrated form that you mix with water according to the manufacturer’s instructions.

Cordon off your lawn with tape, streamers, balloons, or some type of barrier. Keep the kids and your pets off the lawn and away from the yard. Glyphosate is a relatively benign herbicide, but it is a pesticide, and children and pets have lower sensitivity thresholds to chemicals than adults.

Make sure that you follow the label instructions and wear a long-sleeved shirt, long pants, rubber boots, and plastic gloves. Wait the specified time for the herbicide to work and then rake off any debris. Your lawn should be grass- and weed-free at this time, but be sure to make another application if you feel it is necessary.

When you’ve finally decided that all weeds and remaining grass are gone, wait one week before you plant your new expensive grass seed.

For those of you who prefer not to use toxic synthetic chemicals to kill the old grass and/or weeds, you can take several approaches to getting rid of weeds without chemicals.

Rent a tiller: For a modest-sized yard with not a lot of weeds or dense turf, till your lawn area to a depth of 4 to 8 inches, rake out the grass and weeds, and till again. Keep tilling and raking until all the green matter is gone. Dump all this material in your compost bin where it decomposes over a period of months.

Credit: “Horns & Tiller,” © 2008 , Lisa Brewster used under a Creative Commons Attribution 2.0 Generic license: http://creativecommons.org/licenses/by/2.0/legalcode

Be sure to get a tiller that has the rotating tines in the rear behind the tires. They easier to handle than the tillers with the tines in front and over the engine. Running a front-tined tiller is like trying to control a bucking bronco.

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Don’t try to till dry or very wet soil. Water the whole area, let it dry for a few days, and then till.

Renting a sod cutter: You simply guide the sod cutter over your old weedy lawn, and it cuts the turf at just below soil level. Turn the sheets of grass upside down where they will decompose and add nutrients to the soil. You also can haul the sod to a recycling center that accepts yard waste.

Using black plastic: If your lawn is less than 1,000 square feet, buy enough heavy-gauge black plastic to cover your entire lawn. Spread the plastic out over the lawn and weigh down the edges with stakes, or rocks. Without sunlight, grass can’t grow and eventually dies. This process can take anywhere from a month to three months, depending on how hot and dry your season is.

Plowing: Plowing is another method to use if your lawn is rather large. Adjust the plow blade or blades to dig the soil to a depth of 6 to 8 inches. Rake off the weeds and debris and keep plowing and raking until you get rid of all the unwanted green matter.

*Bulldozing: If you have a really large area, a bulldozer or Bobcat may be a good option. Adjust the blade so that you’re just scraping off the thin layer of grass and weeds. You don’t want to take off the soil layer.

About This Article

This article is from the book:

About the book authors:

About the Authors Lance Walheim, former staff garden writer for Sunset magazine, is the nationally recognized author of over 30 widely read garden books, including The Natural Rose Gardener and Hungry Minds’ Roses For Dummies. The National Gardening Association (NGA) is recognized for its bimonthly National Gardening magazine and prolific work in science education for children. NGA is also the coauthor of Gardening For Dummies. Roses For Dummies. Perennials For Dummies. Annuals For Dummies. and Container Gardening For Dummies.

Preparing For Overseeding

Thatch is an accumulation of surface roots, dead plant parts and other debris on the soil at the base of the grass plants. While a thin layer of thatch does not normally present a problem, it must be removed before overseeding to expose bare soil for the new seed.
If the thatch layer is thick, consider renting a dethatching machine or a “power rake” to loosen the thatch and simultaneously scarify the soil without pulling out existing grass plants. With a thin layer of thatch, a very close mowing of the lawn and a brisk raking with a garden rake will do the job. Either way, rake up the loosened thatch and use it as mulch around the yard or store it for later use in a compost bin. See Dethatching Rakes in the Tool Shed.

Deal with Existing Weeds

Many annual weeds die out as fall approaches so they are not a problem when overseeding at this time of year. However, if your turf shows a significant number of broadleaf weeds, which are often perennial and will return next year, remove or kill them before overseeding. Judicious use of the herbicide 2,4-D will efficiently rid the turf of dandelion, plantain, ground ivy and their ilk.

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Because the vigorous, dense turf that results from overseeding will discourage future weeds of this kind, this is likely to be the only time you will need to use this herbicide. Spray it as directed on the product label at least ten days to two weeks before you plan to sow grass seed. Broadleaf weeds will start to turn brown in three or four days and be completely dead by the end of the 10 day wait. The herbicide will have begun to break down after ten days, so new grass seedlings will not be harmed. What remains is bare soil to be overseeded. See Lawn Weed Control Products in the Tool Shed.

Using Broadleaf Herbicide

Read the label carefully and follow the instructions.
Spray when weeds are actively growing (by late summer weeds have abundant, mature foliage).
Skip one mowing before spraying so weed foliage offers maximum surface for the herbicide application.
Plan to spray 10 to 14 days before the date scheduled for overseeding.
Do not spray when rainfall is expected within six hours.
Do not spray if winds exceed 5 mph to avoid drift onto other plants.
Do not walk on, or allow pets and children to walk on sprayed area for at least 12 hours; a 24 hour wait is better.

Aerating the lawn is always beneficial and–if time and energy permit–while preparing for overseeding is a good time to do it. It is not essential to the success of overseeding, though.
Punching holes in the turf soil by means of a mechanical or hand aerator introduces oxygen into the top layer where plant roots grow. Existing grass benefits enormously. It also loosens the soil to make it easier for seeds to contact soil and sprout and new grass seedlings to become established.

Mow Lawn Close and Remove Debris

The most important step in overseeding is preparing the seed bed with an existing turf already in place. Since the grass seed needs to contact the soil and the new grass seedlings need lots of light to grow, it is necessary to mow the existing grass very short.
Set the mower as low as it will go–so its cuts at about ½ inch–to remove as much foliage as possible without scraping or harming the crowns of the existing plants. If you have a bag attachment collect the clippings in the mower bag. Then rake up the area or go over it with a blower-vac to be sure that no debris covers the bare soil between the existing grass plants. See Grass Rakes in the Tool Shed.

Spread Fertilizer (Optional)

It is a good idea, but not critical, to spread some slow-acting granular fertilizer when you are overseeding. This will be your fall (or spring) application of slow release nitrogen fertilizer for the lawn. There is no need to spread lime on the lawn when overseeding. Since it takes six months for lime to begin breaking down and affecting the pH of the soil, it will not influence the environment of the newly germinated seed. See organic lawn fertilizers. in the Tool Shed.