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Weed Killer Tips

Improve your lawn. Eliminate weeds and keep them away with minimum time and effort by choosing the proper herbicide and applying it in a timely way. This works for both grassy weeds and broadleaf weeds.

By the DIY experts of The Family Handyman Magazine

Overview: Targeting weeds

When my wife and I bought our house, the lawn was filled with weeds. Dandelions and ground ivy mostly, with a few generous patches of clover and thistles. I poured some weed killer into a dial-up sprayer, hooked the sprayer up to my outdoor spigot, doused the entire lawn, and an hour later I was done. Within a couple of days, the weeds were wilting, and they didn't grow back after I mowed them. Not bad for an hour's worth of weed treatment!

While I don't claim to have the best-looking lawn on the block (my neighbor is a lawn fanatic!), it is weed free. In this story, we'll show you how to kill your weeds in an hour or less. Although there are hundreds of kinds of weeds, they all fall into one of three categories—broadleaf, annual grassy weeds or perennial grassy weeds—and specific types of herbicides target each weed group.

Whether you want to eliminate weeds before they start growing again (early in the year is the best time to attack weeds) or kill weeds that are already overtaking your lawn, we'll show you how. Most of the weed treatments you need are available at home centers, and the others at garden centers. — Brett Martin, editor.

Kill broadleaf weeds: Early season

A broadleaf weed is any undesirable lawn plant that isn't a grass. The plants have actual leaves on stems, and contrary to the name, many have narrow rather than “broad” leaves. Dandelions, plantain, ground ivy (creeping charlie) and ragweed are a few of the most common broadleaf weeds.

Before broadleaf weeds start growing in the spring, apply a product called Hi-Yield Turf & Ornamental Weed & Grass Stopper Containing Dimension, which is a preemergent herbicide. It kills weeds before they sprout from seed and even kills some weeds that have just started to grow. Spread the product on the yard between your first and third mowings in the spring. The company says a single application will last a full 120-day season. This is as close to a one-size-fits-all magic bullet as you'll find for eliminating annual weeds. No other product on the market will target both broadleaf and annual grassy weeds and stop them from growing. It's available at lawn and garden centers (call first to make sure). A 35-lb. bag treats up to 15,000 sq. ft.

Park your broadcast spreader over a tarp or on the driveway (grains may leak out, and a heavy dose of herbicide on the yard can kill even healthy grass). Fill the spreader (Photo 1) and distribute the herbicide evenly over your lawn.

Kill broadleaf weeds: Late season

If a few broadleaves pop up in the yard (you can always count on a few dandelions), spot-kill them with a post-emergence herbicide such as Ortho's Weed-B-Gon MAX (a 32-oz. bottle of concentrate covers 16,000 sq. ft.). Look on the label for “broadleaf killer” then check to see which weeds it targets. Some broadleaf herbicides also kill crabgrass. There's no need to treat the entire lawn, just the weedy areas. Don't let them spread and create a bigger problem.

Premixed herbicides are OK if you have a small lawn and only a few weeds. Otherwise, buy concentrates to mix yourself— they're a better value. Wait until the temperature is between 60 and 85 degrees F. (The herbicide vaporizes too soon in high temps, and weeds don't grow fast enough in low temps to absorb the chemicals.) Mix the herbicide with water (follow the directions) and pour it into a small pump sprayer. Keep the nozzle 6 to 12 in. from the weed and spray until the leaves are slightly wet (Photo 2).

Kill broadleaf weeds: Too late

If your lawn has lots of weeds scattered over large areas, don't waste time spot-spraying individual weeds. Killing the weeds is as quick and easy as spraying the weedy area with a hose.

Pour a concentrated postemergence herbicide (the same kind you used for spot-spraying) into a dial sprayer and set the dial on the lid to the manufacturer's recommended mixture (such as 2 tablespoons per gallon of water). Attach the sprayer to a garden hose, turn on the water, and apply an even treatment to the weedy areas in the yard (Photo 3). Apply the herbicide when the weeds are actively growing in the late spring and early summer. You don't need to drench the weeds. A light misting will kill most weeds (if it doesn't, give them a second dose in a week). Spray only on a calm day. Even a slight breeze can carry vapors that can kill plants (anything that kills broadleaf weeds will also kill flowers or decorative plants and could harm trees, so watch for overspray).

Tip: Only spray the weedy areas of the yard— not the entire lawn. You'll introduce less herbicide into the environment.

Kill annual grassy weeds: Early season

Annual grassy weeds sprout from seed each year. The weed dies in the fall, leaving behind seeds that germinate the following spring. Crabgrass is the most notorious grassy weed, but there are others, like yellow foxtail and nutgrass.

Use a preemergent herbicide to kill annual grassy weed seeds in the spring before they germinate. Crabgrass preventer is the most common, but you might as well apply a herbicide containing Dimension in the spring because it also kills broadleaf weed seeds. Crabgrass often thrives along sidewalks and driveways because the ground is warmer there, so be sure to apply herbicide in those areas.

Kill annual grassy weeds: Late season

The best way to handle a few scattered annual grassy weeds is to spot-kill them with a postemergence herbicide that's formulated for grassy weeds, such as Ortho's Grass-B-Gon. Look for Grass Weed Killer or Crabgrass Killer on the label (Crabgrass Killer kills other grassy weeds too).

Mix the concentrated herbicide with water (per manufacturer's directions), then pour the mixture into a handheld sprayer. Spray the individual patches of weeds (Photo 1). To ensure that there's plenty of plant material to absorb the weed killer, don't mow the weeds just before applying the herbicide or for three days after. If you don't kill annual grassy weeds now, you can expect them to seed and produce even more weeds next year.

Tip: Always read the herbicide's label before applying to make sure it will kill the targeted weeds and not harm your lawn.

Kill annual grassy weeds: Too late

There's only one remedy for yards taken over by grassy Weeds—spray the entire lawn with a postemergence herbicide (like the ones used in the “Late” stage). Mix the concentrate with water in a pump sprayer (Photo 2).

Spray the yard with the herbicide in the late spring or summer. Apply just enough to get the weeds slightly wet. The weeds should start to die within five to seven days. Spot-kill any weeds that are still growing after seven days.

Kill perennial grassy weeds: Early and late season

Perennial grassy weeds come back every year, just like your lawn grass, and are the toughest weeds to deal with. That's because the herbicides that kill these weeds will also kill your grass. Perennial grassy weeds like Dallis grass and quack grass have deep, expansive root systems that make it impossible to kill them by pulling them out. Quack grass is easy to identify—three or four days after you've mowed your yard, quack grass will be noticeably taller than the surrounding grass

Early Season
To spot-kill the weeds, apply a nonselective herbicide, such as Roundup. Nonselective herbicides kill plants and weeds alike, so it has to be applied to the individual weeds by hand. Wearing cloth gloves over plastic gloves, wipe the herbicide directly onto the weed (Photo 1). Don't worry about covering every single blade. As long as you get most of them, the herbicide will absorb into the weed. It'll take seven to ten days before the weed starts to die. If it's not dead after two weeks, wipe on a second treatment.

Late Season
The solution is the same later in the year. But the longer you wait, the more work you'll have since these grasses continue to spread all spring and summer. The herbicide is most effective early in the season when grasses grow the fastest. As the weeds take root and become sturdier, they may require more applications to fully kill.

Kill perennial grassy weeds: Too late

Once there are too many weeds to spot-treat by hand, it's time for draconian measures. Kill everything and start over. Spray a nonselective herbicide on the weedy area (Photo 2). Wait two weeks. If they're not dead, spray them again.

Once the weeds are dead, mow them as short as possible. After spraying the herbicide, wait 14 days to plant new grass so the herbicide won't kill it.

Photo 1: Wet the bare spot

Photo 1: Wet the bare spot

Photo 2: Cover the seed

Photo 2: Cover the seed

Photo 3: Spread a faster growth mix

Photo 3: Spread a faster growth mix

How to Restore Bare Spots

Killing large patches of weedy areas is going to leave bare spots in your yard that will need to be replanted with grass. The best times to reseed are the spring or fall when the temperature is 60 to 70 degrees F. To start, water the bare spot until it's wet to a depth of at least 3-1/2 in. Water at intervals throughout the day (for about 15 minutes every two to three hours) rather than continuously. With constant soaking, the water just runs off. Check the depth of the water penetration by digging into the ground and lifting up the soil (Photo 1). You'll be able to see or feel how deep the water has seeped in.

Make a series of 3/8-in.- deep recesses in the ground, 1 in. apart, with a square-head shovel. Spread the grass seed over the bare spot. Then flip over a garden rake and use the “knuckles” to cover the seed with soil (Photo 2). Lightly water the area in the morning and evening until the grass starts to grow in.

If you want the seed to grow fast, plant Scotts PatchMaster, which is grass seed with fertilizer and mulch to keep the seed from drying. After making the recesses in the ground, spread PatchMaster seed over the bare spot (Photo 3). Water twice daily.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • Leaf rake

You may need a broadcast spreader, a small pump sprayer, a 1-2 gal. pump sprayer, a dial sprayer, a garden hose, a shovel, a plastic bucket, rubber gloves and/or a cloth glove.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

Various herbicides as required

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