Cephalocereus senilis: Old Man Cactus
The popular ‘old man’ introduces us to the vast realm of columnar cacti. Naturally the cactus purchased at the florist’s is only a small specimen but if it could be grown in congenial conditions for several decades (this being the time necessary for it to reach its true proportions) then it would measure up to 15 m (50 ft) in height!
Young plants (the ones usually available) are covered with long, soft white hairs, which practically hide the body from view. The stem under the hair is greatly furrowed, the number of ribs being 20 to 30. The edges of these are thickly set with areoles.
Adult plants, when they are about 6 m (20 ft) high, develop a cephalium at the top of the column — the ribs change into spirally arranged tubercles covered with areoles which produce a thick cover of spines. Such a cactus looks like a member of the ‘royal guard’ with his shaggy headgear. Theare produced from the cephalium. These are almost 10 cm (4 in) long and 7.5 cm (3 in) across and coloured white and pale yellow. After pollination they are followed by the fruit, which is a lovely red colour and contains a large number of seeds in the dark red pulp.
The substrate for this cactus must be free-draining and should contain some lime, therefore limestone rubble should be added to the compost. Grown in ordinary pots, columnar cacti are not as attractive as if put in a dish arrangement where the bizarre stems of the succulents make a more striking effect. The dish should be simple in design — ideally buff-coloured ceramic ware. Also very attractive is a group of large porous rocks planted with small species of cacti or other succulents. Since most cacti have more or less the same requirements there is no need for the grower to fear failure.