For many vegetable gardens, eliminating weeds is vital for for proper growth. Weeds compete with vegetables for much-needed water and nutrients in the soil, and if not controlled can potentially block sunlight from reaching your vegetables as well. Certain products, such as Roundup, are designed to kill these weeds. Used properly they can safely protect your vegetable gardens from such competition.
How Long Should I Wait?
Roundup's website advises that you wait three days after initial application before planting vegetables in a treated area. If weeds remain after the initial treatment and you choose to reapply the product, will need to wait another three days.
This wait time applies only to the area directly treated with Roundup Weed and Grass Killer. The National Pesticide Information Center (NPIC) advises that the active chemicals in Roundup do not spread through the soil, and so only the area that you treat directly will be dangerous for planting.
Apply Roundup directly to actively growing weeds for best results. Avoid spraying other vegetation, or from spraying other areas where you intend to plant immediately. It is best to apply Roundup when the wind is calm so that it does not spread to other areas of the garden and potentially harm other plants. If in doubt about the size of the area treated with Roundup, wait three days before planting anything, just to be safe.
Why Do I Have to Wait at All?
The NPIC cites glyphosate as the primary chemical used to control weeds in Roundup. Roundup's website advises that the solution is about 2 percent diluted glyphosate, and warns that it will kill any vegetation with which it comes in contact. This low dilution allows Roundup to be effective in killing vegetation to which it is directly applied, but prevents it from spreading through the soil or from staying in the soil for a long time after use.
If you were to plant vegetables sooner than three days after applying Roundup, you run the risk of the vegetables absorbing this glyphosate and dying along with the weeds.
Always read the instructions on the label of any weed killer product before applying it to your garden or planting anything afterwards. Roundup and other similar products produce a variety of specialized weed and pest killers, and depending on your product choice, waiting time may vary.