When is a cactus not a cactus?
Shedding some light on the naming of cacti and succulents
Ioften hear cacti referred to as succulents and some succulents as cacti, which isn't always correct. All cacti (about 1,800 species) are succulents and all belong to one plant family. But not all succulents are cacti. Confused? Well I’ll try to explain.
Cacti don't necessarily have spines, but they must have areoles, which are condensed lateral shoots from which flowers, branches, spines, clumps and leaves (if any) originate. These are the feature that identify and define a cactus. Astrophytum myriostigma, flowering in July, is a popular spineless cactus and the areoles show very clearly.
Succulents are found in many plant families and come from all over the world. Some have spines, thorns, prickles like the stem
of Pachypodium geayi and others smooth leaves and stems but none has areoles. All cacti and succulents can conserve water in stems, leaves or roots to cope with dry periods in their growing year.
Star cacti
The genus Thelocactus is gaining in popularity. My T. rinconensis has been flowering at regular intervals since early May. Rebutia neocumingii began its flowering season in late June, demonstrating and producing more than one flower per areole.
Star succulents
Lewisias play two roles – as alpines and as succulents. Many varieties are being introduced. Last year I acquired Lewisia longipetala ‘Little Raspberry’ and 'Little Snowberry'. As I had hoped, they overwintered well outdoors in pots and flowered nicely in June.
Livingstone daisies (also known as ice plants) are probably the most popular succulents with gardeners and lithops the most popular with the more serious succulent growers, but there are a great many other species available.
Eyecatchers which can spend the summer in a rockery include delosperma and ebracteola.