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GENERA  (click on name)             

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    FOREWORD
This plant directory covers some 100 genera, virtually all kinds of cultivated cacti, and is intended as a practical guide for those interested in growing succulents who wish to  expand their knowledge of the basic needs of each genus as to soil, exposure, temperature, water as well as get information about parasite control, propagation techniques, specific requirements and so on. Each entry, ordered alphabetically, contains information about the place of origin along with a brief description of the genus and ends listing the main species; additional notes are provided if any of these constitute an exception.  
At the end of this guide there’s an index of valid genera and cross-references that will help you find plants known by more than one name. Because plant taxonomy may be sometimes confused, there can be different plants known by the same name and different names given to the same plant. Although changes in nomenclature might occur, we will retain the use of the old plant name for the sake of clarity, if that is what a specimen is widely known as or it is still largely used in catalogues and other publications. Still, a cross-reference to the new classification is provided.
It might be important to remind the reader that any guide is to be used judiciously, not as if it represented dogmatic truth; it has to be regarded simply as a means among others  to achieve good results. In this discipline there’s no place for absolute truth; the climatic conditions of a place may have a great influence on the methods of cultivation. For this reason the advice and suggestions given are as generally valid as possible. Let’s not forget this either: many plants are quite tolerant of a wide range of conditions, even when these are less than ideal, and they can grow without any serious problems. Little wonder, then, that other authors have a different approach to this subject, based on different personal experiences and backgrounds, and the fact that they have to deal with problems as diverse and numerous as the whether conditions that pose them.  

    IMPORTANT: SOME FREQUENTLY USED TERMS

    By basic mix we mean a type of substrate composed of 50% good garden soil , 20% fine non-calcareous gravel (1-2 l. diameter), another 20% lava or pumice stone (2 to 5 mm d.) and the remainder 10% being well decayed leaf-mould (beech leaves are preferable).
The mineral mix contains the same materials but in different percentages, respectively: 30%, 30%, 30%, 10%. As for the fertile mix, this is comprised of 30% leaf mould , 30% peat, 20% sand and the remainder 20% is lava or pumice and has a pH of 6. On the other hand, the basic and the mineral mixes have a neutral ph. In a few cases it is recommended to add some limestone to raise the soil ph for those plants preferring a slightly alkaline mix; you’ll find specific information in the entries for such plants. It is understood that this represents a personal view on a quite controversial subject.
 

      A plant requiring ‘average’ water should be treated as follows:

   - Cautiously resume watering  in early spring, allowing the soil to dry out for a few weeks before more water is applied. Gradually increase the quantity and frequency of waterings until the beginning of the summer. If the plants receive too much water early in the season their swollen epidermis might split open thus developing unsightly longitudinal cracks, as shown in picture.
- During the hottest months, cactuses usually slow down their metabolic processes and some of them go dormant; it is best to allow this state of dormancy by reducing watering. Just sprinkle the soil with little water from time to time, especially in the evening hours.
- Come autumn, many species return to growth so they should be given a little more water. 
- During the winter months whe should suspend watering. The soil is to remain dry unless the plant shows signs of water-stress and begins to wither.

-When you’ve poured water allow it to drain completely from the soil. You should not put a saucer under the pot if you want to avoid waterlogging.

     Many people wonder how often they should water their plants; there’s not a simple answer to this question since it is influenced by far too many variables. Indeed, a small clay pot dries out faster than a big and deep one or a plastic container. A potting mix rich in organic matter dries off more slowly  than one with a high mineral content. Other factors are to be taken into account: high temperatures and windy conditions increase significantly the rate of water loss. As a rule, plants with a caudex or tap-root or bearing fleshy leaves need less water than the others; on the other hand, seedlings must be kept evenly moist for at least a few months.
    That is why, rather than saying how many days should pass between two waterings, it is more convenient to indicate how much time you ought to wait before watering once the soil has dried out completely.