Question
We have thousands of weed/volunteer trees growing in a large area of rock in the back yard.  What is the best way to kill them?  I have heard that spraying them with Roundup using a hand sprayer might do the trick.  Have you ever heard of adding liquid soap to the mixture (helps the poison stick to the leaves) and if so, how much?  Thanks...

Answer
Roundup has a surfactant in it already but I have found that if you add a teaspoon per Gal. of liquid detergent this will help the Roundup stick to the leaves better. Beware that Roundup will kill any green vegetation and you need to make sure it does not get on plants not wanted killed.