Question
I have a tall (about 2-3 ft)columnar cactus I bought this summer and it has got the black and grey at the bottom. I watered last night (only water once a month) and this morning it was laying on it's side. I tried to dig it up - but there are some roots still attached deep. I am leaving it alone until I find out how to go about this. I think the problem is my soil so I know what to correct. I don't have lots of light - it's hard in the NE to get it in the winter. Is is saveable? I'd send a pic..but can't see how on this form! Thanks, Lynn  

Answer
Dear Lynn,

Your cactus has rotted from the base. Depending on the plant, watering once a month may be too much, simply because the humidity is so high in the NE. You stil may be able to save the plant. You will nee to cut it about 5" or so above the rotted area. Use a very sharp knife and BE VERY CAREFUL! Always wear leather gloves when working with cacti.
Try not to crush the plant where you cut. If you see what looks like a black spot in the cut area, that means the rot is traveling up the plant. Cut another 2" off. When you no longer see evidence of rot, let the plant heal for at least 2 weeks. Ib the mean time get a new pot and some "cactus mix" soil from a local nursery and replant it.
Only water if the soil is completely dry, maybe once every 2 months through the winter. If you see new growth in the spring give it a good soaking. If you want to send a picture, please send it to [email protected]. If you happen to have an African Euphorbia, the process to save the plant will be slightly different. Hope this helps.

Sincerely,

Greg