Gardening

with Lee Mullen

Flowering spiny beauties

Cactus flower
Sea-urchin cactus (echinopsis oxygona)

Cacti are usually thought of as spiny horrid things that never need watering and can be a nasty piece of work to handle! But these imaginations are so far from the truth!

They are ideally designed for life with little moisture but do best with even and moderate irrigation in summer. Many species have spines, hair, and waxy skin, which protect them from the sun and predators. The swollen “leaves” are actually enlarged stems, which allow less water to evaporate through transpiration than regular leaves.

Some cacti produce beautiful flowers, some of which are night-blooming, as they are pollinated by insects or small animals, principally moths and bees. Cacti range from small and round to pole-like and tall, such as the Saguaro, which is almost a tree in size. Cacti are known as the desert rose in the Americas because arid desolate regions can become a mass of colour literally overnight making them so appealing.

A good number of cactus species are cultivated for use in ornamental gardens. Some cacti bear edible fruit like the common prickly pear, found growing in alleyways and on roadsides. Not all cacti can “escape” the garden and grow wild like these!

To grow cacti successfully, first and fore mostly they need a sunny position as they prefer hot and dry conditions. However, plants bought from a garden centre grown in shade will need to be acclimatised first. Cacti are best planted in very well drained soil with small amounts of organic matter like compost. As a rule, be very careful not to over water. Let the soil dry out completely between watering during summer and water even less during the winter.

For fertilising, use a formula designed for cactus like an NPK (Nitrogen, Phosphorus, Potassium) 7 — 40 — 6. Use a mixture with a low nitrogen, as cacti can be burned by it.

For propagation, cacti should be germinated in sandy, well-drained compost. A commercial sterilised cactus mix works fine. Use small ceramic pots 5cm x 5cm since they allow soil to dry out completely (after germination) and prevent root rot. Most cacti germination temperature should be around 20°C.

Usually, cacti are disease free, but occasionally, especially if the plant is over watered, any part may be susceptible to rot. If the roots are infected, then most probably the core is also and the plant is lost. If an above ground part of your plant is affected, the area should be cut out with a sharp knife to remove any infected matter. The cut parts should then be dried and dusted with yellow sulphur or fungicide. Also watch for Mealy Bug.

Recommended cacti varieties:

  • Echinocereus — hedgehog cactus
  • Echinopsis — sea-urchin cactus
  • Ferocactus — barrel cactus
  • Mammillaria — fishhook cactus
  • Opuntia — prickly pear
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