Planting a viable garden means getting rid of weeds. Roundup uses the active ingredient glyphosate to kill plants indiscriminately, so it's best to use it before you plant flowers or vegetables in your garden. Roundup doesn't leach through the soil to plant roots, but it can remain on the surface for a short while, harming plants if you add them immediately after spraying weeds. Instead, wait at least a day for flowers and three days for vegetables.
When you spray a ready-to-use version of Roundup, it can begin working in as little as six hours, according to Roundup distributor Scotts. If you want to till the weeds under the soil, it's best to wait until the weeds are dead; if any roots are still alive, they might grow back after you plant the garden. Scotts recommends you wait longer to plant edible plants than ornamental plants to ensure the vegetables and herbs don't absorb any residual chemicals that might then make it to your table
Don't mix it to strong, fallow the label and make sure you don't walk thru where you have already sprayed. It will leave dead foot prints in the grass. Don't ask me how I know that. ;:;banghead