Most of us have seen desert cacti, perhaps looking rather unloved and dusty on a window sill. It needn’t be like this! Their flowers are simply spectacular and they are among the easiest of plants to grow and care for. In this blog I’ll tell you how to grow and care for desert cacti as houseplants, and how to make them bloom.

**Top tip**  Dust cacti carefully with a small paintbrush or blusher brush.

What is a desert cactus?

Desert cacti are spiny succulents, part of the large and varied family of cacti. They store water in order to survive in the warm semi-deserts and savannas where they grow. These areas have low moisture, dry air, bright sunshine and good drainage.

Notocactus minimus. Cacti

Notocactus minimus. Taken by Laitche and in the public domain.

What is the secret to growing cacti?

In a nutshell, give them an environment as near as possible to their natural habitat and allow them to follow their natural pattern of dry season followed by rainy season. Let them rest in their dry season, and then increase watering for their rainy season, when the flowers come out.

Most desert cacti need a dry season of rest in the winter before flowering in their 'rainy season' of spring or summer. But some need to rest in the summer and will flower in the autumn, so do check the individual needs of your cactus.

Temperature, light and air

Cacti are happiest in a sunny, airy position all year round.

A south-facing window is the ideal position if you’d like them to flower. Contrary to general belief, cacti don’t like to be baked, they just like average warmth from spring to summer. Open the windows on hot and sunny days because they need fresh air, and in a greenhouse they may need shading.

In the winter, cacti do like to be kept cool – about 10-12C is great. A cool, unheated bedroom is often the best place. The plants can tolerate temperatures down to 4C, but move them off the window sill if it’s very cold.

Watering

For watering, rainwater is better than tap water. That’s because the minerals in tap water build up in the soil and can cause deposits on the plant. Make sure the water is tepid.

Your watering timetable

About April: increase watering.

Late spring to late summer: treat cacti as normal house plants, and water them thoroughly when the compost dries out. To help flowering, feed from time to time with a high potash fertiliser (such as tomato or a special cactus fertiliser).

Late summer: water less.

After October: only give enough water to stop the plants from shrivelling.

Parodia ayopayana, Lanzarote, Canary Islands. cacti

Parodia ayopayana, Lanzarote, Canary Islands. © H. Zell and reused under https://creativecommons.org/licenses/by-sa/3.0/

How to make a desert cactus bloom

Summer care and winter neglect, as I’ve described, encourages desert cacti to produce new growth – and that’s what most of them flower on.

Flowering is also stimulated when the plant is slightly pot-bound, so don’t put them in too big a pot. And they like a good, gritty, porous compost, not just sand.

With plenty of sunshine and a cool winter rest, many varieties will flower on a windowsill, although some prefer to be in a greenhouse or conservatory.

Most will flower by the time they are three or four years old, although some are much slower.

Seven flowering desert cacti to try

  1. The sea urchin cactus, Echinopsis eyriesii, has ball-like or oval stems. Its 15cm (6 inch) long flowers are scented.
  2. The peanut cactus, Chamaecereus silvestrii, grows quickly and produces red flowers in early summer.
  3. Lobivia is a good cactus for the beginner. It is compact, about 8-15cm (3-6 inches) high, and produces red or yellow blooms readily.
  4. Mammillaria are popular, compact and free-flowering. Mammillaria bocasana is a cluster-forming silvery plant, bearing a ring of small white blooms around the stem in spring.
  5. Some of the Notocactus are spherical with yellow blooms, but Notocactus leninghausii is grown for its columnar stem rather than its flowers.
  6. Parodia are small ball-like cacti and bear flowers from an early age.
  7. Rebutia are small and start to flower when young.

Don’t neglect your cacti, treat them right and they will flower beautifully.