Can I use Roundup to kill the weeds in my perennial garden which slopes into a pond with fish?
Roundup only moves thru plant tissue and roots, not thru soils and mulch, but will also travel in water. So keep it away from the pond, and try to not spray before a rain, or at least time the spray so it becomes rain-fast. Otherwise, once it hits soil or mulch, it locks up, and breaks down. By the way, use it on a ‘no wind day’ to prevent any drift from hitting your desirable plants or drifting into the pond. To be safe, take a milk jug, cut out the bottom, place the jug over the plant to be sprayed, and spray thru the top of the jug. For smaller desirable plants, do just the opposite. Jug over the good plant to protect it, and then spray the weed.