by Richard Pearman

Created on: June 24, 2009

When I first told my wife that cacti grew wild in Alberta, Canada, she didn't believe me. Then we went out to Drumheller and found some Opuntia polyacantha. In addition to Alberta's three native cacti, there are a number of others that can be grown in gardens here. When we got a house, I built a rockery in my south facing back garden and planted some cacti and succulents in it. I've also had some experience of growing cacti in England, which has a warmer but wetter climate.

This article's going to use some Latin names of plants. You can easily look them up on the Internet. It will mainly deal with two groups of cacti (family Cactaceae): opuntoides (sub-family Opuntoideae), which are basically the prickly pears, chollas and club chollas and globular cacti (an informal sub-group of the sub-family Cactoideae), which are those small round cacti that have pretty flowers (read more about them). However Maihuenia is the only genus of the sub-family Maihuenioidea. These are all desert type cacti, the forest cacti (Pereskia, Schlumbergera etc.) aren't very hardy.

Perhaps it's fairly obvious but to grow cacti outdoors in a cold climate, you really need a well-drained site, like a rockery (although it rather depends on how wet your climate is). You should also have the main slope of your rockery facing south (in the northern hemisphere) so it makes more effective use of the sun's rays (in nature cacti are often found on south facing slopes) The type of soil isn't that important. My rockery uses a mixture of peat, loam and gravel, according to advice for alpine rockeries. If your local soil is alkaline, it would help to make it more acidic (e.g. by adding peat). This site should also be well lit and preferably with a building or something on the north side to shelter the plants from the harsh north wind.

You should leave a lot of space around opuntoids as they tend to grow very fast and also have nasty spines and barbed hairs called glochids. You could plant Sempervivums (hardy leaf succulents often used as place holders on alpine rockeries) around them, which can be removed later. Globular cacti (and probably Maihuenias) need to be watched to make sure they don't get smothered. You can add variety by having other succulents on the rockery: Sempervivum, Sedum, Lewisia etc.

I once met a woman who claimed that she'd grown Myrtilocactus geometrizans (one of the large tree like cacti - not known for its hardiness) outdoors in northern England for a number

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