Roundup is trade name for a herbicide manufactured by Ortho. The herbicide is a glyphosate that will kill most all plants down to the roots. Preparing a vegetable bed for plants may include the application of this herbicide. Since Roundup will kill most plants, it should be applied in early spring or late fall when no vegetable plants are in the raised bed. Caution must be exercised during application as any over-spray may harm and kill any existing vegetation.
Mix Roundup according to the manufacturer's listed application rates. This may include the identification of the types of weeds or plants that need controlling. Mixing the herbicide too weak will be ineffective.
Apply the herbicide in early spring prior to placing or planting vegetables in the raised bed. Best time to apply the weed killer is on a calm afternoon when the sun is shining and the weeds are dry. This will allow the herbicide to dry on the leaves of the unwanted plants.
Observe the raised bed one week later. Most if not all of the plants should be either yellowing or brown. If some of the plants are still green, make another spray application.
Apply the herbicide again in the late fall after vegetable harvest. This will eradicate any later germinating seeds and plants. Make a second fall application if the weeds show signs of green as described in step 3 above.