Are these container plants? If so, any fertilizer appropriate for houseplants would be fine for the cactus. A "special" kind isn't required.

If these are container plants, are you using a bagged medium of some kind? If so, an 'organic' fertilizer won't be particularly effective/efficient. But there are organic houseplant fertilizers on the market.

If the plant(s) are growing in the soil, then you can use whatever you use for the rest of your garden.

Removed duplicate post.

This post was edited by rhizo_1 on Sun, Nov 10, 13 at 11:35