I would like to start a garden in a spot that has been lawn. Should I use a herbicide to kill the grass before I turn the soil?
McLennan County Texas
Ideally the process would have started this past summer. You would have plowed/tilled the area then used herbicide as green plants came back after tilling. I would have recommended plow once, then spray, then plow next time something green came up, etc. That would have allowed you to control warm season and cool season plants.
It will be much harder to establish a "weed/grass free" garden if you are wanting a garden this year. You can use a glyphosate and let it sit for weeks, allowing the herbicide to work. This is only going to kill the top growth which will be cool season plants, it does not provide any type of pre-emergent control. You need to be careful on which herbicides you do apply as some will leave a residual and be active in the soil. Glyphosates are contact type herbicides and residual levels would be extremely low.
The challenge will be the warm season grasses and weeds that will emerge (plus weed and grass seed will start germinating) about the first week of April. That is when the soil temperatures will be warm enough to start that process. You will have a new influx of weeds/grass once the soil warms up. Depending on when you are wanting to plant your garden you will probably have to do some weed and grass pulling also.