Cacti occupy a special place among the entire variety of houseplants and differ from them both in appearance and in keeping conditions. In Hellas, cacti (kaktos), the ancient Greeks called any prickly plant like a thistle, growing in abundance in nature. Much later, Columbus introduced the first cacti to Europe, rare amazing plants appeared in the collections of the royal botanical gardens.
In 1571, the French botanist Matiaz Lobel, co-authored with Pierre Pena in the illustrated book Adversaria Stirpium Nova, described 1,500 species of various plants, indicating the settlements where these species were collected, and Melocarduus echinatus (modern name Melocactus caroli-linnaei) turned out to be here. And in 1753, the famous Swedish botanist Karl Linnaeus used this word "Cactus" in his two-volume work "Species Plantarum," while all the discovered and described plants were included in the only genus - Cactus.
The cactus family came to Europe exclusively from the New World, i.e. North and South America. With the exception of the genus Ripsalis, which was found in tropical areas of Africa, but, according to scientists, got there artificially, or rather with migratory birds. Now cacti are widespread, have taken root and become native in the Mediterranean, South Africa and Australia.
But the main range of distribution of cacti is mainly South and North America, Mexico is especially rich in the variety of cacti. Most cacti grow in places where prolonged periods of drought occur, some are found in extremely dry conditions, for example, the Atacama Desert (Chile is the driest desert, cacti of the Copiapoa genus Copiapoa grow there).
First of all, it must be said about cacti that they all belong to succulent plants (succulents are plants that have the ability to store or accumulate water in their cells). Most cacti do not have leaves, or rather, the leaves have been modified into spines, and the function of photosynthesis characteristic of all plants is performed by stems.
By the way, cacti (overwhelmingly) are characterized by the CAM type of photosynthesis, characteristic of many succulents, when the separation of CO2 assimilation and the Calvin cycle occurs. Transpiration, during which carbon dioxide penetrates through the stomata, and malic acid salt is formed (malate - accumulates in cell vacuoles), does not occur during the day, as in ordinary plants, simultaneously with photosynthesis, but at night. In the afternoon, when the stomata are closed, this acid is decarboxylated, and the released carbon dioxide enters the Calvin cycle, and participates in the process of photosynthesis. Such a system allowed cacti to adapt to high light intensity, elevated temperatures and drought.
The stem of a cactus is called its body, or trunk. The stems of some cacti in nature reach a height of tens of meters, real trunks, so Pachycereus Pringla Pachycereus pringlei, native to Northern Mexico, is the highest cactus in the world, the maximum height recorded by naturalists is 19.2 m. Another giant, also native to Mexico and California - Cereus giant Cereus giganteus. Its growth rate, like that of our Russian birches and pines, is very slow, and the average trunk size is 15-17 m. But one of the smallest cacti is Blossfeldia tiny Blossfeldia liliputana, its diameter is about 1 cm.
A feature of any cactus that allows you to distinguish them from other succulents (some are extremely similar to cacti) is that they have areoles. The areola is a modified axillary kidney that is a growth point. According to the same principle as ordinary plants have apical and lateral buds, the cactus has an apical areola, the so-called axilla and lateral areoles.
Many cacti are able to stop growing from the axilla at some point and begin to develop shoots from the lateral areoles. This ability is genetically assigned to individual plant species. That is why mammilaria "babies" are so easily formed, and cereuses literally grow in a pillar. It is from the areoles that the cactus grows spines and flowers appear (in some species of cacti, flowers do not appear from the areola, but next to it, literally breaking through the epidermis, is typical, for example, for echinocereuses).
Areoles, more precisely their size, shape, color of the bristles, location (distance between the areoles), as well as the number of spines (radial and central - growing exactly from the center of the areola), are an essential feature that determines the ratio of cactus to a specific species. Some cacti from areola secrete a sweet syrup, solidifying, it looks like sugar crystals, and the same sweet taste. When too much of this syrup is released, it is better to remove it from the cactus carefully with tweezers or a needle.
Spikes and spines on cacti serve not only to protect against predators, but also to protect against the sun. Even though the spines are usually thin, often very rare, the sun moves throughout the day and each spine always casts a shadow on different areas of the stem.
Therefore, the more spines the cactus has and the thicker they are, the more adapted the plant is to the direct scorching sun. Cacti with short, sparse, or almost no spines usually require sun protection during the hottest hours of the day.
Another interesting feature is that cacti do not form inflorescences, the flowers are usually single, bisexual (with the exception of some species), and do not have a peduncle. Moreover, in the cactus, part of the flower is an extension of the stem, while the lower part of the corolla tube has areoles, setae and spines. This applies to almost all cacti, with the exception of mammilaria.
Sometimes a budding bud turns into a baby (usually this happens when overfeeding with fertilizers). In some cacti, only one flower appears, each time in a new place, in other cacti during flowering, many flowers are formed throughout the stem (aporocactus), in others the flowers form a crown - they are located as a wreath on the top of the trunk. The sizes of the flowers can be from microscopic (a few millimeters) to very large - 15-20 cm in diameter. The color of cactus flowers can differ in a huge variety of colors and shades, however, cacti do not have blue and black flowers, only shades of brown can be the darkest.
Some cacti bloom easily every year, some bloom extremely rarely or only under the best conditions. Flowering in different cacti can last several weeks, and can only last hours. After flowering, fruits form on cacti, which can also be of various shapes, sizes, and often covered with spines.
Cactus stems have various shapes. It may be ribbed, wrinkled, and have tubercles or papillae. The ribs can be vertically flat, spirally twisted, or have a slight bend. The severity of the ribs is sometimes almost invisible, sometimes the ribs are deep and sharp. And spines can be completely different shapes, lengths, structures and colors, some cacti have no spines at all. In appearance, cacti are so diverse that more than one book is devoted to their description. It happens that completely unrelated cacti look so similar that they can be confused, but there will always be a difference, as a rule, it lies in the structure of the flowers.
Cactus classification
The cactus family includes four subfamilies that have a fundamental difference in structure and physiology:
Peresky subfamily Pereskioideae
Currently includes only one genus Pereskia Pereskia (17 species) - cacti, which have completely preserved their real leaves. Representatives of this subfamily are mainly shrubs, with round stems and flat leaves, from areoles that are in the axils of the leaves, there may be spines, usually straight and stiff. The cactus flowers of this subfamily can be single on pedicels, or can be collected several in racemose inflorescences. Most Peresky fruits are edible.
Interestingly, Pereskia is of great evolutionary importance - it is actually a visual aid for the transition of one form of plants to another, combining the signs of different plants - they have photosynthesis mainly according to the C3 type, as in ordinary leaf plants (mesophytic type of metabolism), but a more detailed study by Presky showed that at night there is still a slight increase in carbon dioxide in the tissues, which indicates a low level of CAM-type (only in some species). (Photosynthetic pathway variation in leafy members of two subfamilies of the Cactaceae, Martin, Craig E.Wallace, Robert S., 2000).
In addition, pereskii have areoles and spines, like all cacti. Of course, the spines themselves are not a sign of a cactus, you say - that's right, but the Peresky areola and spines are located on the flowers, and this is already an exclusively cactus sign. Moreover, pereski is characterized by such a phenomenon as proliferation - when new daughter flowers or subordinate shoots are formed from the areola on a flower tube or ovary.
Description of Peresky species
Peresky subfamily
Opuntioideae subfamily
Includes 5 tribes - these are shrubs that have juicy flat or cylindrical stems. All prickly pears have a characteristic segmented stem structure, but in some, stem segmentation is very weak.
The smallest prickly needles (glochidia) are characteristic only of the prickly pear subfamily. In addition, prickly pears at a young age have modified leaves that fall away with age. The flowers are solitary, regular in shape. The fruits of many prickly pears are edible.
Opuntia prickles, as well as peresii, also have a proliferation phenomenon. As for photosynthesis, in studies of representatives of this family, gas exchange processes were recorded throughout the day, in the Opuncians there is a combination of CAM-type and C3-type photosynthesis.
Maihuenioideae subfamily
It includes only one genus (2 species, previously included in Peresky), whose representatives grow at an altitude of 2000-2400 m above sea level in the Andes (territory of Argentina and Chile).
Plants are similar in appearance to opuncia, but glochidia are absent. Like prickly pears, maihuenias have tiny, up to 10 mm juicy conical leaves, and the shoots very much resemble the sprouts of deciduous plants. Despite the pronounced succulence, the plants of this subfamily do not have CAM metabolism - their photosynthesis proceeds according to the C3 type, like Pereskia Pereskia, the absorption of SO2 occurs during the day.
Plants are rare and are practically not found among domestic cacti.
Subfamily Cactoideae
It makes up more than 80% of all other cacti, this is what is called typical cacti. Their main difference is that the leaves are completely absent, and they do not have glochidia either. Cactus stems are usually whole, with no division into segments except in the genera Hylocereeae and Rhipsalideae. The predominant majority have spines. The flowers are sessile, open remain during the day or only at night. Seeds are small 0.1-2 mm, mostly black, glossy.
Among cacti there are many edible plants - plants from the genus Stenocereus, Hylocereus are specially cultivated for the sake of fruits. There are edible ones among the genera Echinocereus, Ferocactus, Mammillaria, Myrtillocactus, Pachycereus, Peniocereus and Selenicereus. The natives of Bolivia even bake cacti of the species Neowerdermannia vorwerkii and eat them like potatoes.
It should be noted that the study of genetic biologists does not stand still, many classification issues remain controversial, and it is likely that the classification of cacti may change again in the near future.
Brief requirements for soil, temperature, lighting - the article contains reference characteristics for the requirements of certain types of cacti for temperature, illumination, soil composition, etc. There are characteristics of the root system and the origin of each genus and species of plant.
In conclusion, I would like to say about cacti that it would be a mistake to consider them all unpretentious plants. It is not entirely clear why in all literature, as a conspiracy, they write about the unpretentiousness of cacti, because in fact this is not at all the case. For different authors, the idea of unpretentiousness boils down only to the fact that cacti do not require frequent watering. But water is not the only condition for plant life.
Judge for yourself, the excess water - and the cactus rotted, the lack of light - a twisted ugly stem, fed with organic fertilizer - and the cactus can die, transplanted into too large dishes - the cactus may not bloom and even hurt for a long time, and the fact that most cacti require cold wintering, doesn't it say that these plants need special care?!
Undoubtedly, there are among the cacti and especially unpretentious, which easily bloom and do not require much attention, but there are not many of them. Therefore, a novice cactus lover should especially pay attention to the nature of the future pet.
It is also worth adding that many cacti are prone to probing the stem when a brown crust appears on the bottom of the trunk, usually in the basal zone. It is formed from contact with moist soil if it dries for a long time, especially if the water is hard, contains a lot of salts, especially from excess fertilizers in top dressing. The salt brown crust on the cactus is simply defined: if you try to chip the crust (for example, with a toothpick), you will find healthy epithelial tissue of the stem, but of a lighter shade (after all, ultraviolet light is not available). However, you do not need to tear off such cork salt growths, the cactus will still be spoiled, and you can easily injure the plant.
Brown crusts and spots can appear higher along the trunk from sunburn, pests, mechanical damage.
