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You may have heard people say that cacti only flower once every seven years.
lobivia This is not true, once a plant is old enough, it should flower regularly every year.
Some plants will flower after only two or three years from seed.
Others need to be much older, perhaps as much as 100 years old before they will flower.
Cactus flowers may be red, orange, yellow, white, pink or magenta, but never blue. They might be bold and spectacular, or more delicate.
echinocereus flower opuntia flower
christmascactus flower What’s different about the flower on the right?
All the flowers shown above are round, and even in shape. This one isn’t, it’s an unusual irregular shape.
Flowers that are irregular in shape are known as zygomorphic.
This is a Christmas cactus, but there are other cacti with similar irregular flowers.
A Spiny Gallery
Most cacti have spines. In the wild they help to protect the plant from some of the hottest sun and discourage animals from trying to eat them.
There are many different types of spines, and some of them are very beautiful.
There are long ones:
And ones which make fascinating patterns.
If you have any cacti yourself have a look at the spines to see how many different types you can see.
Growing cacti at home
Many cacti can be grown in the house providing a few simple rules are followed.
Cacti need plenty of light. A south-facing window sill is ideal, or the conservatory if you have one.
Try to give them as much fresh air as possible especially during the summer.
Most cacti are adapted to live in dry areas so sitting in a pot of soggy soil will kill them. Always repot newly bought plants from garden centres into a mix of compost (John Innes No 2 is ideal) and fairly coarse grit. Squeeze some of the moist compost in your hand. It should fall apart when you open your hand again. If it seems to stick together add some more grit.
All pots used must have drainage holes and you need to put a layer of grit in the bottom of the pot as well to help drainage.
Water your plants regularly during the summer months beginning in spring when it starts to get warm (usually March or early April).
During warm, sunny weather you might water once a week – but make sure the soil has dried out completely before you water again.
Don’t water when the weather is wet and cold. Remember the best rule for watering cacti is
“If in doubt, don’t”.
Cacti rest during the winter so do NOT water them then. Depending on the weather stop watering some time in September.
If possible leave them in a slightly cooler room during this time.
Epiphytic cacti (e.g. Christmas cacti) are rather different. They can be treated much more like other house plants. Plant them in a rich compost (with some extra drainage material) and water them all year.
Cacti can be bought from most garden centres and some other shops as well. But take a look at some Things to avoid.
Things to avoid
Plants which look brown or shrivelled – they are probably dead.
Plants which have odd-looking, thin and straggly growth – this is called etiolation and means that they have not been given enough light in the garden centre.
Some garden centres sell plants in coloured glazed pots, miniature tin buckets or other silly containers without drainage holes. If you buy these repot them immediately into a pot with drainage holes. If you do not do this these plants will die.
And watch out for insect pests
Mealy bug – small white insects that look like miniature wood lice. The picture shows an adult bug on the left and its eggs, hidden in white fluff on the right.
Root mealy bug – similar to mealy bug but a little smaller, this hides away on the roots of the plant.
red spiderRed spider mite – you never see red spider mite – only the damage it causes. It nearly always appears at the top of a plant, and will grow out into a ring of damaged skin as seen here.
Most pests can be dealt with by spraying with the right sort of insecticide – ask your parents for advice and always be very careful. Don’t breathe in the fumes and don’t spray near your pets.
For root mealy bug wash the roots of the plants in soapy water – make sure you get rid of every trace of the pest and its eggs. Then leave the roots to dry before repotting.
Where do cacti live?
Cacti come from either North or South America where they grow naturally in the wild. Some cacti can be seen growing outdoors in other places with a warm, sunny climate but they have been brought there by man.
Many people think that cacti grow in deserts. Nothing can grow in a true desert – but many cacti do grow in very dry areas which might be known as deserts.
The giant saguaro grows in the Sonoran Desert. This is the second largest desert in North America covering parts of California and Arizona and stretching over the border to Mexico.
As deserts go this receives quite a lot of water – it has two rainy seasons one in the winter and another in the summer, but nothing in between. As you can see the cacti are growing among other plants, all of which are adapted to survive in dry areas.
The Andes is the longest land mountain range in the world. It stretches along the western coast of South America for about 7,000km.
It looks like a bleak landscape, but many cacti are adapted to live in these high regions.
This very old Copiapoa is growing by the coast of South America in Chile. Sometimes years can go by without any rain – but cacti like this manage to survive.
The reason for this lies in the sea. The cold sea water means that cold air moves over the hot land, which produces fog. Usually this happens every morning and the cacti can find the water they need by absorbing moisture from the fog.
Epipytic cacti live in the tropical rain forests that stretch across the north east of Brazil and central America. Conditions are very different here, in many areas it rains nearly every day!
What makes cacti special?
Cacti are special in many ways. Many people think that cacti live in deserts. Nothing can live in a real desert, but ‘desert’ cacti are adapted in many ways to live in dry and sometimes hot places.
Globular cacti – a round shape means less surface area to lose water through evaporation.
Many cacti, both globular and columnar, are ribbed. This means that the plant body can expand quickly to take in water when it is available. The ribs also provide some shade to the plant body.
Many cacti have a thick, tough skin (or epidermis) with fewer stomata (or breathing pores). In addition some are covered by a waxy or oily bloom. Both of these features helps to reduce water evaporation.
Some plants have tuberous roots for water storage. Others have a wide system of shallow roots, which when it does rain can absorb water from a large area of the ground.
Many cacti have spines, which provide shade and protection from hot sunshine. A thick covering of spines like these on the right will also help to prevent the plant from being eaten.
And finally – what makes cacti different from all other plants?
Have a look at the picture below.
All cacti have areoles. They usually look like small cushions of bristles from which the spines and buds are growing. The spines grow from the back of the areole and the buds from the front. No other plant has areoles – they are unique to cacti.
Some other succulent plants have spines, but if they are not growing from areoles, then they are not cacti.
See our Spiney Gallery for pictures showing how spines and areoles can make cacti really special.