Round-up ties up the minute it hits the soil and doesn't move. It's only effective if it hits live plant material. This is when the label says you can plant after spraying:
Special Instructions
All ornamental flowers, trees and shrubs may be planted one day after application. Lawn grasses, herbs, vegetables, and fruit can be planted 3 days after application.
You should ALWAYS read the label on any chemical you use in your gardens, ALWAYS!
I use round-up to edge my gardens. Do not get it on anything you don't want to kill, tho.
