How Soon Can I Plant After Using Weed Killer?

Spraying weed killer is a very common way to deal with areas infested by weeds. Many people spray their gardens before planting time -- to remove unwanted growth and to make room for their chosen plants. The question then becomes, "How long do I have to wait to plant?"

Your chosen weed killer should have information on the label as to how long you need to wait to plant new bedding plants. Read the label carefully, as the instructions for different plant types may vary. For example, the information on two different RoundUp® products state that you can plant ornamental flowers, trees and shrubs one day after application, but not to plant lawn grasses, herbs, vegetables and fruit until three days after application. Weed killers have different strengths and applications, so before you purchase, confirm that you are getting the weed killer appropriate to your project.

The primary active ingredient in many commercial weed killers is Glyphosate, which is absorbed through the plant leaves, causing them to wilt and die. Once it hits the soil, it does not cause a great deal of interference with newly planted seedlings.

Once Glyphosate hits the soil, it begins breaking down and is rendered inert in days to weeks. This makes it less available to plants for absorption and, therefore, less likely to cause problems.