Crabgrass is the most common type of weed in lawns and it's nearly impossible to completely control this weed. Crabgrass is a warm season annual grass which grows best in the heat of midsummer when desirable lawn grasses are often semi-dormant and offer little or no competition. Crabgrass over winters as seed, comes up about mid-May or later, and is killed by the first hard frost in fall. Crabgrass grows best in full sun. It does not grow in shady places. It will come up in clumps and look markedly different from the rest of the grass. As it grows older, it's "arms" will flop over and radiate out from the center covering the ground.
Crabgrass can be controlled in a number of ways, but the best defense against crabgrass is a thick vigorously growing lawn that is mowed no closer than 2-1/2" for cool season grasses. Use a bagger to collect grass clippings while the weed's seed heads are present.
However, you don't want to have unsightly crab grass in your lawn, so to gain control, do not apply fertilizer in summer and get a post-emergent herbicide. This type of herbicide is applied after the crabgrass has already sprouted.
Bentgrass is a cool season perennial spreading grass that is commonly used for golf course greens, tees, and fairways. For the lawn owner, bentgrass is often considered a weed.
Bentgrass is not a viable option for a home lawn because it is very expensive and difficult to cultivate and care for. It is characterized as a very fine-textured, bright green grass with flat, narrow leaves.
Unfortunately, there is no herbicide you can use to get rid of bentgrass that won't damage the lawn you are meaning to grow. Patches of bentgrass will appear as fluffy, fine-textured clumps that you can remove with a spade or by just pulling. When removing bentgrass, do so about 1" into the ground and re-seed. You can try a herbicide with glyphosate to remove bentgrass, but be aware that it will kill the wanted grass along with the unwanted grass. apply the herbicide to an area about six inches or so outside the patch of Bentgrass to kill the individual stems which are creeping outwards from the patch, otherwise, these patches will reemerge.
Apply glyphosate in spring or fall when the grasses are actively growing. Wait approximately seven days, then reseed or sod the area. If you decide to till the soil prior to establishment, and see bits of Quackgrass rhizomes coming to the surface, remove these. Or wait two weeks or so until enough new Quackgrass leaves emerge and kill the new plants with a second application of glyphosate.
Most people are familiar with dandelions. They are a broad leaf weed that begins with bright yellow flowers that eventually change into a globe of fine filaments which are seeds that are distributed by the wind. Who hasn't blown a dandelion into the air?
Even though dandelions are considered a weed, they actually do have some uses in both food and medicine. They are close in character to mustard greens and are sometimes used in soups or salads.
Dandelion root is a registered drug in Canada and is used as a diuretic. It can also be used to treat anemia, jaundice, or to sooth nervousness. And, of course, who hasn't heard of dandelion wine?
If not effectively controlled, dandelions can quickly take over your yard and kill off patches of grass as they rob the soil of water and nutrients meant for the lawn. Simply picking or mowing over the flowers won't get rid of them. Dandelions are best treated during active growing cycle with a spot treatment. If you use a dry granular form of weed killer or a weed and feed type of fertilizer, apply it to wet grass and weeds. The weed control material must stick to the leaves of the weed plants to be effective. If you spray a liquid, apply it only on a calm day so material will not drift onto desirable plants. Remember, broadleaf weed killers are broadleaf plant killers. They do not, for example, differentiate between dandelions and tomato plants. Apply them only to weeds in the lawn. Be careful not to get the material onto desirable plants in your yard. Read and follow all label directions.