Mowing properly is the single most important task you'll do with your lawn; it has the greatest impact on weed survival. As mentioned earlier, many farm weeds never appear in your lawn because they can't tolerate being mowed regularly. Mowing does control some weeds.
Every turfgrass has a specific height that is best for its growth. Any turfgrass that is mowed at its proper height is healthier than one that is mown too short. Short mowing is an invitation for crabgrass and annual bluegrass to invade and become well established. Annual bluegrass is rarely a problem in a home lawn that is mowed at the proper height. If you persist in trying to make your home lawn appear to be a golf green, weeds will invade.
It is mostly the timing of fertilizer programs that influences the growth of weeds. The basic premise is that we want to feed the grass, but we do not want to feed the weeds.
This means that in northern grass areas, the main fertilizer applications take place in late fall and early spring, not during the summer. Grass roots absorb the fertilizers in these late and early spring applications when the annual weeds are not around to benefit. If fertilizer is applied during the summer, annual weeds such as crabgrass will get a full feeding as well.
WEEDS: SYMPTOMS, NOT PROBLEMS
I invite you to turn your gardening thinking upside-down. In any gardening situation, weeds, diseases, and insect pests are not problems. They are symptoms.
Let me give you an example. If you cut your lawn too short, the grass will not have enough leaves to produce energy. This lack of energy will create a weakened, thin grass stand or lawn. Lawns with thinning grass patches (where the sun can reach the ground) are invitations for weeds to colonize.
Remember that nature abhors a vacuum. Old Mother Nature will send plants to cover any bare stretch of ground she can find—that's one of her rules. If your grass is thin because you cut it too short, Mother Nature will fill the bare spot with weeds.
Now, what is the problem? The weeds or the too-short mowing?
You can (repeatedly) spray and kill the weeds or you can simply set your mower deck to a higher setting and make your lawn healthier and more weed-free in the process.
A weed is not a problem. It is a symptom telling you to garden better on your home lawn.
In southern areas, exactly the opposite holds true. Feed the lawn during the summer months when the grass is growing strongly. Avoid the cooler months when the weeds are more likely to appear.
So, if you know what weed you want to avoid, then you can design a fertility program to feed your lawn and not your weed.
The analysis of the fertilizer and the amount you apply are also factors in weed establishment. For example, we use phosphorus mostly as a starter food for young seedlings by putting it on the surface for these small tender roots to absorb and use. In the average soil there is enough phosphorus for normal grass growth a few inches below the soil line where mature grass roots live. In most cases, we don't have to apply phosphorus to our home lawns. Applying phosphorus on a regular basis (remember that phosphorus does not move easily in the soil) to the top of the lawn doesn't feed the grass roots—it feeds the weed seedlings. So, if you want to feed the weed seedlings, apply lots of phosphorus. If you want to feed the grass, hold back on phosphorus on mature lawns.
The first item of business on any weed control agenda must be: Know the weed you are trying to control.
There is no sense applying some chemical to your lawn if you don't know what it is you are trying to kill. It would be like taking a prescription medication to treat an ailment without even getting a doctor's diagnosis.
Once you identify the weed, you can identify whether mowing or feeding or any other of the cultural controls will work on your lawn.
This sounds pretty obvious, but more times than I'd want to tell you, I've had customers come into the nursery for “stuff to kill some weeds.” What weeds? “I dunno—just weeds.”
A word to the wise: Your local extension or agricultural office will have a good book on local weed identification. Get it. It will save you time, effort, and money. Also, check the Web resources at the back of this book for some useful information.
In the chapter on starting lawns, we talked about the need for frequent and light watering when establishing a lawn from seed. This indicates that young seedlings like to be kept damp. Well, if you water frequently and lightly with a mature lawn, you're encouraging the growth of weed seeds and not the growth of the mature grass. Mature grass needs deep watering—and only when it needs it.
It isn't a nice thing to say about some grass seed companies, but there is a difference between good seed and bad seed in the nursery business. You get what you pay for, and if you don't pay a lot for the grass seed because it's a discount brand—you might very well be paying for weed seed. There's no way to tell beforehand what you have in the package, so the cheapest insurance is to purchase only good seed with the appropriate labeling for weed seed content.
Broadleaf weeds are easily controlled on the home lawn using either of these old-fashioned tools: weed spuds or rakes.
A weed spud is an old-fashioned tool that is making a comeback on home lawns. It is a flat strap of steel with a V-shaped gouge cut into one end. The other end is attached to a long handle. You put the V-shape against the root of a weed and lean or push on the handle so the steel strap cuts through the root. It is not hard work. On average-size urban and suburban lawns, it is amazing how quickly an entire patch of dandelions can be cut in half. The dandelion plant regrows in a week or two and the operation needs to be repeated. It only takes a few such cuttings to deplete the energy sources of the dandelion and the plant will die. It's easy work, doesn't require fancy clothes or equipment, and leaves the lawn weed-free and healthy. It does however require patience and commitment to the process.
There are special weed rakes with tines that are quite close together. Pulling them through the grass will remove creeping charlie or ground ivy. These rakes are ideal for removing runners and vine-type weeds from home lawns. Again, more than one raking is going to be required to control the problem.