Question
Hi there,

A neighbor gave me a cactus that's over a foot tall and quick
thick around, with vertical ridges and quarter inch spikes just at
the top, which I think was because someone removed them. The
areoles are scarred. At the base it is shriveled, soft and brown.
About half the base is affected from the soil up about three
inches. What should I do?  

Answer
Dear Joel,

Your plant is rotting, but it may not be a total loss. Since half of the base is still good, try not watering for a while and let the rotten part dry up. However, if the rot continues to spread, cut off the top 8 to 9 inches of the plant. If there are black or brown spots, larger than your pinky finger, it's time to get a new plant.

If there isn't any spots or they are very small, let the plant "heal" for at least a couple of weeks, then replant. It will take a few months to root, so be patient. Hope this helps.

Sincerely,

Greg