What can be done?      
A thick green lawn will do much to help keep weeds to a minimum.
With Ontario’s new Cosmetic Pesticide Ban, keeping weeds out of lawns is going to be more difficult than in the past. The products that are currently available do not work as effectively or as efficiently as the traditional, now banned, weed killer products.

There is a new product or two on the horizon that are supposedly going to be much more reasonable in effectiveness and cost. But that is still in the future.

There are 2 approaches to weed management.
1. Concentrate our efforts on building a strong and healthy turf population to crowd out and resist weeds. Many of our customers with reasonably healthy lawns are choosing this method and have elected to use our Root Proliferator treatment to boost root density in the soil profile. Weed treatments per se are not used.
2. Use the weed management products that are currently available but recognize that they may fall short of the expectations that we have been accustomed to in the past. Spot treatments are used to combat existing weeds. (up to 25% coverage).  Not all weeds are susceptible to these treatments.
(Severe problems with weeds will require extensive and more costly applications. Cost will be dependent on your individual weed situation.)

Please pull a few weeds when you see them starting to sprout. Even if you get only half of the root of a small dandelion, it will probably die. On the other hand, leaving 10% of large dandelion root behind is often enough for that dandelion to sprout up again.

Ways to discourage weeds using the first approach of building up the lawn include:
 Granular Compost applications- adding organic matter to improve soil structure
 Root proliferator treatments- to crowd out weeds
 Aerating and overseeding- to improve turf density

Please call if you would like to add any of these types of treatments to your program

THINGS YOU CAN DO to maintain a thick, green and healthy lawn.
 Watering -Water deeply. Light watering encourages shallow rooting which makes for weaker grass and thatch formation. Water about once a week on average. The lawn needs about 1" of water per week. Check your sprinkler by placing a tin can on the lawn to see how long it takes to get 1" of water on your lawn.
 Mow right away. Don't allow the grass to get too long between mowings. If you cut off too much at once, the grass will go brown. Removing more than 1/3 of the plant is very hard on the roots. Keep your blade sharp.
 Mow high. Keep your mowing height at 3" for most of the season. A higher cut will provide more shade and keep the soil cooler and moister. The extra shade also discourages weeds, crabgrass and insect pests. Mow shorter near the end of the season, especially the last cut.
 Thatch- Excessive thatch favours disease development, and will harbour insects. Aerations are one way to reduce thatch. Rake the lawn in the spring to dislodge surface thatch.
 Fill in bare or thin areas with new grass. Weeds and crabgrass are less likely to get started in your lawn if you can get grass growing first. Grass seed will grow fairly early in the year before crabgrass or many weeds are active, but will sprout at any time if kept constantly moist. Fall is the best time to seed (Late Aug thru Sept). Use “endophytic” perennial rye seed– turf type grass that naturally resists insects.

Weed Grasses
To many homeowners, any grass that doesn't look like the Kentucky bluegrass sod that they had when the lawn was new is a weed grass - many call that weed grass "Crabgrass". Actually, there are several undesirable grasses that can invade the home turf.

Crabgrass has run rampant in many lawns the last few summers. Crabgrass is an annual- this means each autumn it dies- but each spring it comes up from seed. It germinates in mid May. By the time it is noticeable, you see short, light green, grasses along the driveway or walkways and in the thin areas of the lawn. It grows quickly, and before long it spreads out flat, often smothering the existing grasses. The leaves are now distinctly hairy, and long seed heads develop. As it gets cooler in September it turn purple. Later it dies and by spring it is gone.

Control of Crabgrass . A healthy thick lawn will naturally crowd out crabgrass. Regular feeding and aeration help to develop thick lawns to discourage crabgrass and other weeds. Mow the lawn at 2 1/2 to 3 inches high. Water deeply once a week (on average) rather than every other day. Crabgrass can be controlled because it dies in the winter. Products are available that kill the seedlings as they germinate in the spring. If necessary, resod bare spots. Re-seeding will also thicken the lawn. Add grass seed in the fall (as early as late August). Fall is the best time because crabgrass controls can interfere with lawn seed germination. (Normally we avoid putting crabgrass controls on newly seeded areas so as not to damage grass seedlings. - Of course, without the control, crabgrass may sprout in these areas). The new seed will fill any spots left thin by the crabgrass. Add the seed even before the crabgrass dies- the crabgrass will protect the newly germinating grass plants. 
Bent Grass
Any grass in a lawn that is undesirable is a weed grass.  Actually, there are several undesirable grasses that can invade the home turf.
Bentgrass is great for the golf green. It is noticeable for its very fine textured blades, light green colour and above ground stems that often lay flat on the soil surface. Often you will find the stems laying on the surface will have roots starting to grow on them. it is used extensively on the golf green because it will tolerate being cut very short.

It is a problem on home lawns because it is shallow rooted and thus requires a great deal of pampering. It is easily damaged in the winter and then takes much longer to green up in the spring. With shallow roots, it does not have the ability to draw moisture from deep in the soil, and tends to turn brown with the hot, dry weather. The stems often turn brown, exposing dead areas when the lawn is mowed. Bentgrass grows vigorously and will spread very quickly in home lawns.

Control of Bentgrass.
As with quackgrass there aren't any products that selectively control bentgrass. If you find a small patch remove the grass and resod. If you have more than you care to dig up, rake hard in the spring to remove as much as possible. Set your mower up hight- at least 2 1/2 inches. When your lawn is mowed short, bentgrass is better able to tolerate the close mowing than for instance Kentucky Blue grass. Use an infrequent watering routine as this will discourage the shallow rooted bentgrass. If there is a lot of bentgrass, a new lawn is the only way to get rid of bentgrass. Incidentally, when mowing, mow the areas with bentgrass last. Small pieces of bentgrass will root in other areas if the right amount of moisture is available

Crabgrass in the Summer
What can I do with crabgrass in my lawn?
Some suggestions and tips-
Unfortunately, there is no longer a post-emergent product that can be used on crabgrass at this time of year.
Any top killers that will kill crabgrass will burn the lawn grasses as well, which tends to make the lawn with temporary dead spots. This can look even worse than the lawn with crabgrass.

The good thing about crabgrass is that it will die when we get cold weather in October. The bad part is that they can produce a lot of seeds for next year.

This year- Hand pull as much as possible
Make sure mowing height is at least 3" high. Crabgrass likes warm soil temperatures. The extra blade length provides a little more shade to keep the soil cooler. Going from a 2" mowing height to a 3" mowing height may not seem like much, but that extra 1" is 50% more grass blade.
The extra shade also reduces water evaporation, reduces the chance of chinch bug problems, and helps reduce weed germination.

Crabgrass tends to grow in the weaker and warm areas. The warm areas are along pavement and patios where the hard surface transfers heat to the soil adjacent. Make sure when trimming that the lawn along the edges is not trimmed too short.

Weak and thin areas- Thin areas do allow the soil to get warm. Warm enough to allow crabgrass to get a foothold. When the lawn is thicker, there will be less crabgrass.

Fall is a good time to thicken your lawn with overseeding. Mid-August through September is the ideal time to increase density of lawns. The night temperatures are cooler and water does not evaporate as quickly. This is Mother Nature's grass seeding season (and when the sod farmers do their seeding, too.) Spring seeding is second best, but seeding at that time of year can be tricky if you put on the crabgrass preventer as it can interfere with grass seed germination)

Of course, regular and professional applications of a high quality granular fertilizer three or four times per season helps to increase tillering in Kentucky bluegrass. A fancy way to say it increases density and thickness.

In the spring, consider using a crabgrass preventer to reduce crabgrass germination. The old crabgrass preventer is now banned. There is an organic alternative. Not as effective, and more costly. The pesticide product lasted for 12-16 weeks, the organic one lasts about 4 weeks. It will hopefully reduce crabgrass germination, but is not always fool proof.

Quack Grass     
To many homeowners, any grass that doesn't look like the Kentucky bluegrass sod that they had when the lawn was new is "Crabgrass". Actually, there are several undesirable grasses that can invade the home turf.

One that is particularly troublesome is quackgrass. In late April or early May many people will call complaining about the crabgrass in the lawn. If the grass is in the lawn in May it is NOT crabgrass. Crabgrass isn't up and visible that early in the season. Most likely it is quack grass (also called twitchgrass) or one of several other grasses that can be treated as quackgrass.

Quackgrass -  this weed grass is often mistaken as crabgrass. Its leaves are coarse, wider than the regular lawn. If you find "crabgrass" in your lawn in April or May, it is most likely quackgrass as quackgrass lives through the winter. Quackgrass is generally most noticeable a few days after the lawn has been mowed. It grows quickly - You cut the lawn on Tuesday and it seems that by Wednesday night the quackgrass is already higher than the rest of the lawn. The new growth is light green, older blades have a blue-gray-green colour. If you pull on the grass you may find white underground stems.

Quackgrass is very deeply rooted. This means that is able to survive the lack of moisture better than lawn grasses. Quackgrass can continue to spread even in drought conditions.

Control of Quackgrass is not easy. (these instructions will also work for other weed grasses) There are no products that selectively kill quackgrass. In other words we cannot spray the whole lawn and control only the quackgrass.

If you live in a jurisdiction that permits the use of Roundup or other products that contain glyphosate see below.

In the province of Ontario, Roundup and other glyphosate products can only be used for proscribed uses such as the control of Poison Ivy.

There aren't any products that do a very good job of eradicating quack grass. There are no easy or quick solutions.

Vinegar and fatty acid herbicides will kill of the tops of the quack grass, but it will re-grow from the roots. If the quack grass is growing on your patio, you can apply these products every few weeks. As soon as the quack grass start to shoot up some green foliage, give it a spray. Over a period of time, the food stored in the roots will slowly become depleted, the plant will become weaker and will slowly die. This process is much harder to do when the quack grass is growing in your lawn. Here having dead patches of grass will likely spoil the appearance of the lawn.

If the area is small, digging up the quack grass may be an option. To do this thoroughly, you must remove at least 8 inches of soil, sometimes more. All of the long pieces of underground stems (they are white and look like coarse roots) must be removed. Quack grass can grow back from pieces left behind that are as short as a couple of inches.

If the area that is infested is large and you are thinking about resodding, you could rototill the area. The first problem with this is that a rototiller will chop  up the quack grass roots into hundreds of small pieces. So now instead of twenty plants you may now have 700 pieces of roots that could grow. If you are going to rototill, it is best to be prepared to not have a lawn for a while. After rototilling, some roots will be on the surface, rake up and remove as much as possible. If the rototilling is done during the hot summer weather, the roots that are on the surface or near the surface may dry out and die if they do not receive enough moisture. Once the roots near the surface have died, rototill the soil again to bring new roots to the surface closer to the sun and heat. Unfortunately, this is not a fool-proof method and will require at least several rototillings to kill off much of the quack grass.

On an ongoing basis, mow the lawn regularly at a 2 1/2 to 3 inch setting. Do not allow the quackgrass to grow tall. When the quack grass grows tall, it is able to create food and store it in the roots. Keeping the quack grass cut short will lessen its ability to manufacture food.

Regular fertilization programs will help to crowd the quackgrass as turfgrass responds better to feeding than quackgrass

Control of Quack and other Grasses if Roundup (glyphosate) is available.
A non-selective herbicide such as Roundup will control quackgrass very well. Problem is- it will also control your lawn grass.

Often, lawns are infested with quackgrass in 25-40% of the lawn. At that point most people say that they are not prepared to do major renovation of half the lawn or more. "We'll live with it- at least it's green."

If you have quackgrass in a small area, you could do some minor renovating to remove it.

We recommend that you use Roundup to kill all the grass in that small area. Make sure that you confine Roundup to those small areas. In 7-10 days the grasses there will turn yellow. Roundup is absorbed by the foliage and is taken down to the root to kill the whole plant.

If Roundup is available, we do NOT recommend digging up the quackgrass. One customer thought he could. When we came to look at his lawn, and it was a half-acre lot, there were a hundred or more circles of fresh topsoil where he had dug out the quackgrass. However, quackgrass roots are so hardy that a piece of root only a couple of inches long will grow back. At this particular customer's, in a year or two, there was a lot of quackgrass coming up around the newly seeded areas.
After the grass has turned yellow, then you can dig it up. Or if you like, turn it over and sprinkle grass seed or resod.

Tall Fescue     
Tall fescue is a wide-bladed clump grass commonly used in lawns for sports fields because of its tolerance to wear. In a home lawn, many people do not like the tall fescues because 1. they are lighter green in colour. 2. they have wider grass blades. 3. they grow in clumps and stand out from the Kentucky bluegrass.
This textural difference of fescue from bluegrass and the interruption in uniformity makes tall fescue a weed in some lawns.

Tall fescues have been the subject of much improvement and breeding. The resulting turf types make a good lawn if they comprise 100 percent of the lawn. However, when tall fescues are in a bluegrass lawn, you may note that the clumps are tougher and the lawn mower has difficulty cutting them.

Control of Tall Fescue.
First, make sure you do not use a grass seed mixture that contains tall fescues. Tall fescues are sometimes found in less expensive mixtures for cottages and other types of lawns.

You can dig out the clumps, but ensure that all tall fescue roots are removed. Then re-seed or re-sod after removal. You can spray clumps with a non selective herbicide that contains glyphosate. Remember, though that this will harm any grass that it is sprayed on.