Harvey from Vacaville, Ca writes
Grass/Weeds after spraying store brought RoundUp and this grass/weeds continue to grow through decorative rocks, this action needs to be maintained.
Round up can be used to kill weeds under rocks, however a higher water volume is needed to get to the soil below the rocks where the weeds are thriving. Also, keep in mind that roundup will only kill the weeds that have emerged from the ground through the rocks and will not prevent weeds from coming back. You would want to kill any exisiting weeds with a heavy application of roundup, then follow up with an application of a pre-emergent weed control product to prevent new growth. The key with a pre-emergent is knowing what weeds you are trying to stop from coming up so you choose the right product, and timing the application correctly in the spring and fall each year to catch the weeds before the germinate.
Answer last updated on: 01/01/2015
