Question
 thier are no south  or west windows in my house its under a lamp thats turned off at night i believe one problem was overwatering how much does a indoor cactus need to be watered
is it good to put it under a lamp?


Answer
Dear Kim,

Black is usually a sign of rot, which is usually associated with too much water. Generally speaking, a cactus that is indoors needs to be watered only once a month or so. If you put it under a lamp, use what is called a "grow lamp" and keep it on at least 10 hours per day in the summer, about 2 hours less per day in the winter.

Just make sure the soil is dry before watering. Also, depending on the type of cactus, some like water in winter, some in summer. Hope this helps.

Sincerely,

Greg