Many groups of plants that are unrelated to cacti have also adapted to survive in arid regions and often resemble cacti in appearance. These offer examples of parallel evolution: Unrelated organisms subjected to similar environmental stresses often evolve similar anatomical and functional characteristics. For example, many spurges that grow in dry parts of Africa, where cacti are not found, exhibit leafless, spiny, fleshy stems.
Scientific classification: Cacti make up the family Cactaceae. Cacti with fully formed leaves are classified in the genera Pereskia and Pereskiopsis. The night-blooming flowers and the saguaro plant are classified in the genus Cereus. The Christmas cactus is classified as Schlumbergera bridgesii.
Cacti are once more becoming a fashion item; their architectural and spiny shape makes them perfect for the clean lines of today's interiors, their sculptural, unforgiving look matches perfectly the minimalist design of many homes. There is a huge range from which to choose, from miniature dwarf cacti, less than an inch tall, to the giant Saguaro cactus, Carnegia gigantea, whose stately form dominates the desert landscapes of Arizona. Many have very tall and very narrow profiles, meaning they can fit in the smallest of spaces in the home. Despite their generally harsh and tough appearance, most cacti will produce flowers, many of the most beautiful hues, totally unexpected and usually surprisingly fast, often overnight, contrasting beautifully with the sharp spines with which most cacti are covered.
Because of the hostility of the environments where they live in nature, cacti are among the easiest of house plants to care for. Not surprisingly they enjoy bright light, and heat, the brighter and hotter the better. This makes them ideal for the conservatory and they are among the very best survivors in those conservatories which are left unattended during the working week, to the extent that the temperatures climb to heights that would kill most other plants in a single day. Cacti love these conditions. Their drought tolerance is legendary and they need watering only once a week or so, less if pushed. They can be stood outside during the summer months in full sun, where they will thrive in the fresh air. Further, bearing in mind that deserts can get bitterly cold at night it should not be forgotten that they are as tolerant of low temperatures as they are of high ones, many will accept below-freezing temperatures as long as the air and their soil is dry. An annual feed completes the picture of their requirements.
For ease of care, sculptural modern looks and their bizarre, colourful and unexpected flowers, cacti are hard to beat as all-round house plants. Slow growing, they will not outgrow their containers for many years.
WATERING
Observe the plants! They will almost tell you when to water, particularly the Succulents.
You may water freely in Spring and Summer when the plants are growing well. Water in the early morning once a week if the plants are in the greenhouse, or once a fortnight if in the house on a window sill. Try not to water on cool or wet days, so that plants have a chance to dry off after you have watered.
When you water, water well and then leave the plants to get on and grow. Watering little and often will bring the roots to the surface and make them susceptible to drought and they will not grow well. Never leave water standing in saucer, just give as much as the plant can absorb and water the compost not onto the plant! In time you should be able to feel by the weight of the pot when a plant needs watering.
Only a few plants grow in the winter, so no water should be given at all from about mid September until the end of March. For Winter growing plants consult an experienced grower until you have more experience.
If you are unsure whether to water or not, do as a Yorkshire man would say: "If in doubt, - do nought!"
Cacti in particular are resilient plants and can go a long time without water.
3 - 4 months after re-potting in Summer, when the plants are growing, you should add some food when watering. "Phostrogen" or "Chempak No.8" is best, but any fertiliser low in Nitrogen but high in Potash is very suitable for all Cacti and Succulents.
WHERE TO GROW THEM
Cacti & most of the Succulents grow in semi-deserts and therefore need the best light we can provide for them.
Of course quite a lot of Cacti and Succulents can be successfully grown on a window sill, but you will have to be a little selective, a good grower will advise you.
If you are fortunate to have a greenhouse, you will be able to grow almost anything, but in Winter you may have to have a source of heat.
There is also quite a range of plants that can be grown without heat, but with the protection from the rain of a cold frame.
Cacti Information
More cacti information...
The flowers of cacti are often large and showy and occur singly rather than in clusters of several flowers. The perianth (floral tube) does not consist of sharply differentiated sepals and petals, but rather of a series of bracts (modified leaves), which gradually grade into sepals and finally into showy petals. The flowers have many stamens; the ovary is inferior and fused to the perianth. The fruits are often brightly colored and fleshy.
Most of the 130 or so genera of cacti are found in cultivation, the small, slow-growing species being most popular because of their variety in shapes, colors, and spines. One of the best-known is a group containing beautiful night-blooming flowers and the familiar saguaro plant. In some classifications, this group is split into as many as 10 separate genera. Still more widely grown is the group containing the Christmas cactus. Species of this group, which naturally occur as epiphytes (air plants) in tropical rain forests, do not fit the popular idea of cacti as squat, fleshy plants of desert regions. Examination of their stems, however, reveals the presence of the cactus family’s unique areoles; their flowers have the typical cactus features.
Cactus, common name for the family comprising a peculiar group of spiny, fleshy plants native to America. The family contains about 1650 species, most of which are adapted to arid climates. The fruits of cacti are important sources of food and drink in many areas to which they are native. Because cacti require little care and exhibit bizarre forms, they are popular for home cultivation and are coming under increasing pressure as a result. More than 17 kinds of cacti now face extinction because of plundering by avid collectors and professional poachers, especially in the southwestern United States and northern Mexico.
Cactus plants usually consist of spiny stems and roots. Leaves are greatly reduced or entirely absent. Only in two genera are fully formed leaves present. The stems of cacti are usually swollen and fleshy, adapted to water storage, and many are shaped in ways that cause rain to flow directly to the root system for absorption. The roots form extensive systems near the soil surface, assuring that a given plant will absorb the maximum amount of water from a wide area; plants in deserts are usually widely spaced.
The most distinctive vegetative feature of cacti is the areoles, specialized areas on the stems on which stiff, sharp spines usually grow. Some cacti lack spines but have hairs or sharp, barbed structures called glocids on the areoles. Areoles develop from lateral buds on the stems and appear to represent highly specialized branches.
