Answer: I am not aware of any weed killers that are safe to use around cactus. The easiest way to remove the weeds would be to water the soil around the cactus, or wait until you get some rain. Then pull the weeds out roots and all (wetting the soil will make it much easier to pull them out). If you want to take a chance, you can spot treat the weeds with Round Up. If you shield the cacti with cardboard and carefully spray Round Up only on the weeds, the cactus should be safe. Round Up does not move in the soil and it degrades in the presence in sunlight and fresh air. Without any residual action, the cactus should be safe. Once you get rid of the weeds you can apply a "pre-emergence" weed killer that will keep weed seeds from germinating.
Q&A Library Searching Tips