How to Keep a Cactus Alive. If you seem to lack a green thumb, you are not alone. We've all killed a cactus or three at some point. Common cactus ailments include rot, fungus, dull complexion, wilting, and a stunted growth due to poor light, poor soil, neglect, or too much water. If your cactus is about to kick the bucket, here's how to bring it back to life without too much effort on your part.
Determine what kind of cactus you have. Go online or find a book on common cacti and compare pictures and descriptions to figure out which cactus you are dealing with before you begin the rescue mission.
Learn the basics. There is a plethora of pertinent information on cacti growing, but unless you want to make cactus gardening a major hobby, focus on the basics. This means learning what kind of cactus you have, which soil it prefers, and how to pot, repot, and prune your cactus.
Check the soil. Most cactus plants need sandy soil and lots of direct sunlight to thrive. Buy a special cactus mix of potting soil, or create your own layering gravel, sand, and all-purpose potting soil.
Relocate the dying cactus to a warm, sunny location away from drafts or heat sources. If it still does a perk up, it's time for a transplant.
Repot your cactus into a larger, terra cotta pot that is fairly shallow and wide with excellent drainage. As you transplant the cactus, prune any dead or wilting roots with sharp scissors but be careful not to trim too much at once or you'll make the cactus more vulnerable to root rot and fungus.
Gently wipe the dust off the cactus with a damp paper towel. If it's too spiny for this, fill a bowl with lukewarm water and a dab of dishwashing liquid and swish the cactus gently to get rid of an accumulated dirt or dust. Let the cactus recover on a paper towel and repot in a few days, and the cactus should bounce back within a week or two.