Prickly pears tend to be something of a joke. This is unfair. They can be beautiful plants if well grown and can have a rugged beauty if not so well grown; have pretty flowers; most are very easily cultivated. Some are very hardy and can add interest to a garden in a cold climate. There are about 200 species, varying from small plants to shrubs and trees. They're natural flora in much of the Americas. They have value as food and pigment production and can be used as grafting stock for other cacti.
Prickly pears belong to the family Cactaceae, sub-family, the Opuntoideae, sometimes called Opuntiads. This also includes plants with sausage shaped stems and ball shaped stems etc..
Opuntiads have leaves but they're often very small and short lived, as with prickly pears. The distinctive feature is glochids; small, barbed hairs, which come out when the plant is handled. The stems are normally fleshy and divided into sections, called joints, pads or cladodes. Like all cacti, they have areoles (hairy patches, just above the leaves, baring the glochids and spines) and are perennials. The seeds are large for cacti, oddly shaped, light colored and have a reputation for being hard to germinate.
Prickly pears comprise the genera: Airampoa (Tunilla), Consolia, Tacinga and Opuntia; the last having the vast majority of species.
The flattened sections of a prickly pear are not leaves, they're joints. The real leaves are small scales on new growth. The areoles are found both on the edge and forming a diamond pattern on the flat sides of the joints. Flowers are normally produced from areoles around the edges of young joints. The ovary looks like a small joint but is round in cross section. The petals are rounded with many stamens, which normally move towards the stigma when touched. All species are self-incompatible, so it's necessary to cross-pollinate two clones to get seeds and usually fruit.
The seedling has a long hypocotyl (stalk) and two large, fleshy, cotyledons (seed leaves). It then grows a more obviously cactus type stem. At first the stem is cylindrical (round in cross section) but changes to the typical flattened prickly pear growth after one or two years.
Any approximation to normal desert succulent treatment will normally suffice. Some require minimum winter temperatures about 10ºC but most will grow fine with temperatures going down to around 0ºC and some will survive much colder conditions.
Growing from cuttings is very easy. Just remove a joint, leave it to dry for about a week and then plant it.
Some of the more noteworthy kinds
Airampoa are very small plants from South America, mostly with red or orange flowers.
Consoleas are large shrubby plants from Cuba.
Consolea rubescens (road kill cactus) – a sizable shrub or tree, growing up to 6m tall. It has oddly shaped, spineless or weakly spined joints and red, orange or yellow flowers.
Opuntia is a huge genus with very varied species. The classification is rather confused and many seem to hybridize in habitat. At one time most the Opuntoideae such as Cylindropuntia and Tephrocactuswere classified in this genus. Some genera that were once considered separate are now generally considered to belong to this genus.
Opuntia auranticaca (tiger pear) – a shrubby South American plant 50-100cm high with only slightly flattened joints, which are dark green with purplish brown markings. It has long, brown barbed spines and yellow flowers.
Opuntia basilaris – a small North American prickly pear, branching from the base to form groups of heart shaped, purplish joints. Normally spineless with magenta flowers but can have yellow flowers. Looks very similar to O. aurea.
Opuntia brasiliensis (Brasiliopuntia - Brazil prickly pear) – As the name suggests, this comes from Brazil. It has a cylindrical main stem and flattened branches with thin, dark green, waxy joints. There are a few brown spines. Grows up to 6m high and has yellow flowers.
Opuntia chlorotica – a North American shrub up to 1.5m high with bluish-green joints and yellow flowers.
Opuntia cochinilifera – a shrubby species up to 3m tall, with thick, weakly spined joints that are dark green, tinged purple. The flowers are red and only open just enough for the stigma and stamens to stick out. This has long been cultivated as the host plant of the cochineal insect from which red dye for food and cosmetics is made.
Opuntia englemannii (Engleman's prickly pear), common in the South Western US and northern Mexico. This is shrubby up to 3.5m tall and variable spines and usually yellow flowers.
Opuntia ficus-indica (Indian fig) is probably the archetypal prickly pear, forming a moderate sized shrub. It was widely cultivated in the Americas in Pre-Columbian times and it's origin is uncertain. It has now been naturalized in many places. Many cultivars exist. It's fruit and young joints are eaten and it's fruit is also used to make preserves and alcoholic drinks. It's also used as a host plant for the cochineal insect.
Opuntia fragilis (brittle prickly pear), has a huge distribution over much of North America, including parts of Canada, getting close to the Arctic circle making it the most northern cactus. It's also probably the hardiest. It's a small, sprawling plant with thick, often only slightly flattened joints. It has variable spination and normally yellow flowers. As the name suggests, the joints are easily detached, a means of asexual reproduction. Some populations are thought to consist of only one clone. Some clones seldom flower. This makes a good grafting stock.
Opuntia humifusa (Eastern Prickly pear) is wide spread on the east side of North America with two small populations in Canada (however many rather different plants have been lumped into this species, perhaps confusing the picture). Typically it's a small, sprawling plant with spineless joints and reddish-brown glochids. The flowers are yellow. Some of the southern forms are tall and shrubby.
Opuntia microdasys (bunny ears cactus) is a common house plant in colder climates. It's a small (about 50cm high), shrubby Mexican species, spineless with typically orange glochids, but there are various forms with different sized joints and glochid colors. There's even a cultivar with wavy edged joints.
Opuntia polyacantha is a small sprawling plant. As the name suggests, it's very spiny with normally white spines. It's also one of the hardiest species, extending into parts of Canada. The flowers are normally yellow and are followed by dry fruit.
Opuntia spegazinii is a small shrubby plant from South America. It has long, thin, easily detached, only slightly flattened joints. It often has purplish coloring around the areoles. The brown spines are barbed. It's very free flowering and the flowers are followed by red fruit (pollination doesn't seem necessary), which grow small joints that can be detached and will grow into new plants. Different forms have white, pale yellow or pink flowers and the spines may be restricted to the fruit and the small joints on it or also on the long joints (literature seems inconsistent on what name applies to what form).
Tacinga come from Brazil and like to be kept about 10ºC in the winter. They're spineless but do have glochids. Some species, which were formally classified in Opuntia have recently been transferred to it.
Tacinga funalis is the original species. It has long, sprawling, slightly flattened joints. The flowers are white.
Tacinga imoena is a small prickly pear with the unusual feature of producing some it's small, red flowers terminally. This means that the growing tip turns into the flower – this is common is some plant groups but unusual for cacti.
Hopefully you now see that prickly pears should be taken more seriously and there are a wide variety you can grow in your home or garden. If you live in the Americas, you may well be able to find wild populations near you.
http://opuntiads.com/O/ - Opuntiads of the USA.
http://www.facebook.com/groups/169593409746097/ - Facebook group for Opuntiad enthusiasts.