Weed killers can be a welcome alternative to bending over and trying to yank weeds out of the ground, roots and all. The effectiveness of your weed killer depends on what type of weed you use it on and where you use it. Knowing what works best, and under what conditions, can greatly enhance the beauty of your garden and lawn.
Getting the Most from Your Weed Killers
To maximise the effectiveness of the weed killer you use, first determine what you want to accomplish. For example, if you want no vegetation at all in a particular area, the most common and effective weed killer is Glyphosate (N-(phosphonomethyl) glycine). This chemical is the active ingredient in Roundup, made by Monsanto, but it's also available generically now that Monsanto's patent has expired.
Glyphosate is an excellent application for paved or gravelled areas, where you obviously don't want any vegetation growing, and it also works extremely well when trying to remove old grass and other vegetation from an area in which you plan to replant. Whether getting rid of old grass and weeds, to sodding or seeding a new lawn, to planting a flower or vegetable garden where the old lawn grew, you'll find Glyphosate very effective. Just spray the area completely, and within about a week you'll find the old plants turning brown and dying. You'll have to wait about a month before replanting again, but once you do, the area should be clear.
You can also use Glyphosate to kill weeds in your garden as an alternative to pulling them, but you need to be extremely careful to keep it off the leaves of the plants you don't want to kill. Glyphosate is a general herbicide, which means it will kill any plant--including the ones you want--and it's absorbed through the leaves. It works only on growing plants, however, so it poses no threat to seeds once the active ingredients have been absorbed into the soil. It's also, therefore, not effective as a pre-emergent herbicide.
To effectively control weeds in your lawn, you'll need a weed killer that kills the weeds but leaves the grass alone. The most common and effective product for this type of application is Mecoprop-p, the active ingredient in such spray herbicides as Ortho's Weed-B-Gon. It's also used in granular form with fertilisers as part of "Weed and Feed" formulations. This weed killer eliminates broadleaved weeds while leaving grass undisturbed, greatly enhancing the appearance of your lawn. Broadcast spray applications should be limited to at most two per year, and even spot applications should be restrained, as too much spraying can ultimately kill grass as well.
If carefully used, Mecoprop-p weed killers can leave your lawn looking lush, full and uniformly well-manicured. They're not effective, however, as a pre-emergent herbicide, so you'll need to select another product for that. Also, since they're not effective in killing grass, they won't eliminate unwanted grasses such as crabgrass. For that, you'll once again have to rely on a pre-emergent herbicide to prevent germination in the spring.