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lawn weeds going to seed

Common Lawn Problems: Why is My Lawn Going to Seed?

Every year, usually beginning in the month of May and into mid-June, many lawns begin to show signs of grass going to seed. This is especially noticeable in-between mowing schedules and the grass has a chance to grow taller than its regular height of cut. Many people wonder why this is occurring, if it is good or bad, and how can it be stopped?

Homeowners can rest assured, grass going to seed is perfectly healthy and it’s the natural process for grass to reproduce itself. As unsightly as it may look, there is no real way to prevent the grass from going to seed during this time. Grass going to seed is a good sign the plant is actually healthy and growing well. If it is really concerning, the only way to minimize the appearance of the grass seed is to continuously mow it to remove the seed heads.

Another common question people ask is whether or not this seed will fall off, grow and help fill in bare areas? The simple answer is NO, the majority of the seed produced is from hybrid varieties which means it’s sterile and will not germinate or grow.

If you suspect that you have problems, but are unsure, contact your local Nutri-Lawn and we’ll come out and take a look for you.

Dealing with Lawn Weeds

Spring has officially sprung, but it’s not just bulbs and trees doing the springing.

Crabgrass, chickweed, ground ivy and assorted other lawn weeds also are gearing up now for another season of annoying the heck out of those who lust after pristine green carpets in front of the house.

Before automatically using the old apply-all-kinds-of-stuff-to-head-off-every-possible-problem approach, consider rethinking your options.

For starters, how about easing off the zero-tolerance weed policy? An occasional dandelion or patch of clover won’t get you kicked out of the neighborhood (probably). Look for other ways to validate your suburban lordship and masculinity.

Lawn perfection can be had, but it comes with a price – not only in lawn-care bills but also in its effect on soil organisms, groundwater and runoff into waterways.

A lawn can be nice without being perfect. That you can achieve without chemistry degrees and 12-syllable herbicides.

If you haven’t had a problem with crabgrass, why put down a crabgrass preventer every year at this time?

If you only get a few patches of weeds here and there, why drop-spread a weed-and-feed product all over the whole lawn every May?

But if you DO have substantial lawn-weed problems, a better approach is to shore up your weaknesses by adding more grass seed instead of more weed-killers.

Weeds are opportunists. Bare dirt is their ally. If you beat them to the punch by getting grass out there first, you win.

Early to mid-spring and early fall are the year’s two best windows to thicken up thin lawns with additional grass seed.

You’ll have to decide which way to go because you can’t prevent weeds and start new grass seed at the same time. Most products that prevent crabgrass and other weeds also prevent grass seed from germinating. An exception is siduron (Tupersan). Check labels for when it’s safe to seed after using other products.

Go with a quality grass seed that’s naturally resistant to bugs and disease (variety ratings are available at, and remember that grass seed germinates best when it’s raked lightly into the soil surface and kept consistently moist until sprouting.

What do you do about weeds that come up after you scrap the chemical four-step plan?

Before taking action, know the enemy. The type of weeds you’ve got will determine what you use and when you use it.

Weeds fall into two main camps: annuals and perennials.

Annual weeds are ones that sprout anew each year, live their entire life cycle in one year, and then produce seed for the next generation. Some common annual lawn weeds are crabgrass, goosegrass, barnyard grass, foxtail, black medic, prostrate knotweed, prostrate spurge, common chickweed, corn speedwell and henbit.

Closeup of nutsedge (a.k.a. nutgrass).

Perennial weeds are those that come back year after year. They also may set seed (or send out runners), but unlike annuals, they don’t die out with the season. Some common perennial lawn weeds are dandelions, orchard grass, quackgrass, yellow nutsedge, wild garlic, plantain, creeping speedwell, ground ivy, clover and wild violets.

Annual weeds are best controlled by stopping them from sprouting – i.e. by using those weed preventers now. If most of your weed trouble is from annuals, a reasonable strategy might be to go ahead and use a preventer now and then focus on adding new grass seed in the fall.

Weed preventers include products such as benefin (Balan), benefin and trifluralin (Team), pendimethalin (Pre-M and Halts) and prodiamine (Barricade) as well as corn gluten meal, a non-chemical alternative that’s a byproduct of corn.

What few people realize is that these products don’t prevent weeds all season. They generally work for about 8 weeks – even less in rainy Junes like we had last year.

That means timing is critical for applying them. Put them down too soon, and they run out of steam while annual weeds are still capable of sprouting, which can run into August. Put them down too late, and they’re harmless against weeds that already have sprouted.

In central Pennsylvania, the usual application window is late March to early April – roughly around the time that forsythias flower. To ensure season-long control, a second application should go down in early June.

What you don’t know is whether early summer will bring brutal heat and drought. That alone will stop weeds from sprouting, unless you help them out by irrigating the lawn.

One option to spread out your weed-preventing window and maybe get by with one application is a relatively new product called Dimension. This both prevents new seeds from germinating and kills off young crabgrass and other weeds for the first few weeks after they’ve sprouted. That means you can put it down a few weeks later – about the time dandelion flowers are opening.

For perennial weeds and newly sprouted annuals, the idea is to zap them without harming the grass around them.

A good front-line approach: simply pull them or dig them. When my kids were little, I gave them screwdrivers and paid a nickel a weed, which cost less than a bottle of Weed-B-Gon and kept them busy at the same time.

If you go with a weed-killer, consider a liquid one that lets you spot-spray just the weeds.

Which product you use will depend on whether the weed is a grassy one like crabgrass or goosegrass or a broad-leafed one like plantain or dandelion.

Broad-leafed ones are easier to control, and products are readily available at garden centers. Just be sure to choose a product that’s labeled for broad-leaf weed control in lawns! You may need two treatments to kill some tougher weeds.

Grassy weeds are a little harder to kill because they’re similar botanically to lawn grass.

Products such as MSMA, DSMA and Acclaim are labeled for control of grassy weeds such as crabgrass, goosegrass, yellow nutsedge and the like, but they work best when applied early in these plants’ growth stage. Unfortunately, most people don’t distinguish grassy-weed outbreaks until those weeds are too far along. Even under ideal conditions, it may take two or three applications.

The saving grace is that annual grassy weeds (like the aforementioned crabgrass and goosegrass) die off when frost arrives. But for perennial grassy weeds like orchard grass and quackgrass, you’re stuck with digging out these patches or spraying the infested area with a kill-everything-green weed-killer such as glyphosate (i.e. Roundup).

Then you’ll have to reseed the bare patch. Or else let weeds grow everywhere and tell the neighbors you’re experimenting with wildflower meadows.

More ways to discourage lawn weeds by encouraging good grass growth: * Test the soil to be sure it’s getting the right mix of nutrients at the right levels. Do-it-yourself Penn State test kits – available at county Extension offices and most garden centers for $9-$10 – also give a reading of the soil’s important acidity (pH) level.

* Aid grass root growth by removing soil cores with an aerator each fall to reduce compacted soil. Most lawn weeds tolerate compacted soil much better than grass.

* Cut your grass high – 3 inches is good. Taller grass blades shade out baby “weedlings” and provide a greater chlorophyll supply to maximize the production of growth-generating sugars for grass roots.

* Top-dress the lawn each fall with a quarter-inch layer of compost. This adds nutrition, organic matter and microbes that all aid grass growth.

* Use insecticides and fungicides only if needed, and target them to specific problems.

* Let lawns go dormant in summer droughts. If you do water, do it deeply less often instead of shallow and frequently. Put on enough water that the soil is damp to a depth of 4 to 6 inches so the roots are encouraged to go down after it.

Good resources for identifying lawn weeds:

* County Extension offices, their Master Gardeners and garden centers.

* The book “Weeds of the Northeast” by Richard Uva, Joseph C. Neal and Joseph M. DiTomaso (Cornell University Press, 1997).

Weeds In The Lawn

Americans waste an awful lot of time and money fighting the weeds in their lawn. All that annual angst over which herbicide to try each year can be replaced with one very important weed control step – overseeding the lawn one or two years in a row. Herbicides do kill weeds. What homeonwers don’t appreciate apparently is that when you kill a weed you leave a hole, a space in the dirt. Some folks think that if I add some fertilizer at the same time I kill the weeds, the grass will reproduce and fill that hole. That is not generally true. Another weed is more likely to fill that hole, giving you another reason to use herbicide again next year.

A dense turf mowed at 2 or 2 1/2 inches all season long will allow few weeds to ever develop. You can’t get a thick lawn from fertilizing. You must add more seed, more plants. Thick grass (about 9 to 12 plants per square inch, about what new sod looks like) leaves little space for weed seeds to germinate.

Tall grass that is dense allows little light to get to the soil level blanking out the light that is needed for weed seeds to germinate. So overseeding is your best weed control in the long run. Let’s look at the two most notorious lawn weeds, the dandelion and crabgrass to demonstrate the value of overseeding.

Is it possible to have a truly weed-free lawn? Probably not completely, but you can get close. The trick is, when you kill weeds, you must replace them with grass seed. Do not count on the grass plants reproducing fast enough to fill in the bare spot left by the dead weeds. You want your lawn eventually to be as thick or dense as new sod; about 7 or 8 plants per square inch. Dense turf, mowed tall, has few weeds. Here is how to reach that goal.

There are four levels of weediness in a lawn, and each level is addressed by its own set of tools and techniques.

Over 50% Weeds – The worst case is when you look over the lawn and have to admit that over 50% of your lawn is weeds. In that case, the grass is so thin and stressed it is not worth keeping, so kill the entire lawn – weeds and grass – with a non-selective herbicide such as RoundUp (Monsanto) or KleenUp (Bonide). The active ingredient in this herbicide is glyphosate, and will kill most any herbaceous plant it contacts. Don’t use this on a windy day to avoid harming other ornamental plants. Follow the label directions to the letter. Your lawn should be dead and turning brown in about ten days. At that time you mow the lawn as short as your mower will go and rake up all the debris. Over-seed the lawn and then water two or three times a day, every day, for two weeks.

When you start from scratch like this, you will likely need to overseed again around Labor Day weekend to achieve a thick, dense turf. If at that time there are few weeds, there should be no need for applying any more herbicide, just spread some more grass seed.

20% to 50% Weeds – If you guesstimate that you have more than 15% to 20% weeds without being too scientific about the measurement, the grass can be saved so you only need to kill the weeds while leaving the grass alone. That requires using a “selective” herbicide that kills weeds but not the grass. In most cases, you are going to have some broad-leaved weeds such as dandelion and clover, and you’ll likely have some grassy weeds such as crabgrass. There are several selective herbicides on the market that kill both the broad-leaved weeds as well as the grassy weeds. Bayer’s All-in-One Weed Killer for Lawns is found in most home centers. Bonide’s Weed Beater Plus can be found in most garden centers. When using these combination herbicides you must wait three weeks before you overseed to fill in the holes left by the dead weeds. Again mow short, rake up all debris, spread grass seed and water at least twice a day without fail for two weeks.

Fewer than 20% Weeds – When you have something less than 20% weeds, you are usually dealing only with broadleaved weeds, so you can use a selective herbicide that kills just those broadleaved culprits and leaves the grass alone. Weed Beater by Bonide or Weed-B-Gone by Ortho are both effective for this job.

Again you must wait three weeks before you can lay down seed, but at this level, if your turf is dense enough, you can probably get away with only patching those bare spots bigger than a softball and avoid the task of over-seeding the whole lawn.

Hardly Any Weeds! – Once you have gotten your turf thickened up and continue mowing tall, you should have only a few pesky weeds such as dandelions sneaking in when you are not looking. At this level, a hand weeding tool is really all you need and you can let the grass fill in the hole left by the weed.