Herbicides come in two major forms; there are some that kill grasses and some that kill broadleaf plants. First, I would like to say Roundup is a brand, not a type of herbicide, and it does not kill everything. Now that I got that off my chest, let’s continue.
Grassy Plant Herbicides
Most of the grass killers are made from a chemical called glyphosate which is mostly specific to killing grasses. The best uses for this type are to kill grass in your sidewalk cracks or planter beds. You could also use it to kill off your lawn if you want to replant. There are several options but mainly look for one labeled for your weed and that contains glyphosate.
Broadleaf Plant Herbicides
For broadleaf weeds, two major chemicals are Triclopyr and 2,4-D. These target weeds like dandelions and blackberries. My favorite is a brand called Crossbow because it actually kills my neighbor’s blackberries that creep over my fence. It is specific enough that I’ve actually sprayed these chemicals in the middle of my lawn and the grass was fine.
The herbicides already described work great for growing, already emerged plants. You can reach the advanced stage of herbicides and use something called a pre-emergent. These keep plants from growing when they haven’t already sprouted. They aren’t nearly as targeted and they tend to keep the plants you want from growing as well.
Make sure that you are getting the right chemical for the job and you’ll never be disappointed. Put these chemicals on around 70 degrees, when it won’t rain, and in the right concentration and you’ll be thrilled with the results.