(Grand Forks, B.C.)
Cactus normally have small roots compared to the top of the plant, and can be grown quite happily in a container. There are many tender cactus that like this type of situation; they can be planted fairly close together, or spaced apart with gravel or lava rock mulch between them, or even some driftwood or rocks to make it look like a desert.
Miniature landscapes have always fascinated me, and what could be more fun than a desert in miniature?
Some of the best containers that I use for cacti are hypertufa planters. Cactus seem to fit perfectly into the rugged and rough surfaced handmade pots either alone as a specimen or as a group. In a group planting, one larger type of cactus plant surrounded by several different types and kinds is the best.
The soil has to be well drained. I generally mix some kind of commercial potting soil with half and half gravel, pumice or even lava rock, which is a bigger version of volcanic rock. A drain hole in the pot is absolutely essential. Plant the cactus plants, then don't water the soil for at least a week to allow the roots to heal and callous.
Overwatering these types of plants is the most common cause of death - generous water in the summer can prod them into blooming, but it's important to give them a dry period before this to trigger the bloom cycle.
Cactus planters are commonly found in supermarkets and florist shops, but if you investigate the soil, it most often is some kind of sterilized potting soil that doesn't have enough drainage.
I recommend making up your own miniature desert with some small cacti - using these tips you can create a much more realistic - and happy - cactus planter.