The Ampyx Cactus Centre

Opuntias are among the more primitive of cacti, with a body form that is heavily segmented. Segments may be cylindrical, or flattened to form pads up to 50cm in length. Ultimately, many will become rambling shrubs or small trees. Other, miniature, varieties will live happily in a 10cm pot for a decade. If they grow to maturity you may be rewarded with beautiful flowers in shades or yellow, orange and red, but that is difficult to achieve in pot-grown plants. To develop properly they should be bedded out in a fertile soil - and then the results can be awesome. The end of Ampyx's greenhouse was taken over in the space of about 2 years and dealing with the resulting monster was a major problem.

Opuntias all have two things in common - sharp spines which lodge securely in the skin when provoked, and short, easily detached spines called glochids which occur in tufts at the areoles. Avoid touching an Opuntia since all its spines are sharp and difficult to disengage. It is possible to lift a plant in its pot by the grip of one central spine, so think before you get hold of the plant with your other hand to pull harder.

The brown form
Opuntia microdasys rufida
The plant illustrated here was about 15 years old when it was planted out and given a free root-run. It is a very common, and rather decorative species. The variety with white spiny tufts is often seen for sale in garden centres. All of the yellow, brown or white-spined varieties make interesting pot plants, but the brown one seems tougher and tolerates lower winter temperatures.

The year after bedding-out this chap we were treated to a couple of flushes of blooms, which was a very pleasant suprise. The stamens of the yellow flowers were sensitive, and when they felt the presence of a pollinating bee, would fold up and enclose the poor beast. In this way a thick coating of pollen was transferred to the insect ready for transfer to the next flower. When the flower was finished, the petals dropped from the stem, leaving a cup-shaped joint - you can see one in the centre of the picture - which was still firmly attached. Often, new flowers will arise from the remains of previous flowers, but we didn't see that happen.

Eventually, the competition for space was weakening the smaller plants, so they were all dug up and cuttings taken to regenerate the plants - which is generally very easy with Opuntias. It was an intensely irritating operation, since even the slightest brush against one of these plants will transfer hundreds of short, sharp, penetrating and persistent spines to the unwary hand or arm. Removing them is almost impossible, as they are very brittle and snap off at the least opportunity.

We decided to investigate the reason for this behaviour under a microscope. Here is just one of the spines from the above plant, but seen at a magnification of about 400X. The remarkable barbs on the shaft of the spine can be seen clearly, so it's no wonder they won't let go. Makes me itch just looking at the picture................................

Another strange habit is for the central spines of some species to be encased in a paper-like sheath which isn't prickly and is easily detached. Other varieties have flattened, curled and papery spination. There are others whose body form is a stack of spherical joints. All very strange, and frankly worthy of some patience with their aggravating spines.

Glochid 400X magnification