The Echeverias, growing plant and seed avaibility, miscellaneous (engl) PDF Imprimer E-mail
Echeveria - Echeveria
Écrit par James Low   
Mercredi, 26 Décembre 2007 20:32

THE ECHEVERIAS

 

by James E. Low

 

Previous: More historical detail, hybrids, conservation of rare and endangered species.

 

GROWING, plant & seed availability:


For anyone wishing to collect these species the accessibility of the plants becomes an important factor to know about. Unfortunately this availability is not very good today, except for the few common species usually grown. There does not now seem to be any dependable wholesale growers for almost all of the more unusual types. This includes both seeds and plants. This situation may even be getting worse due to a lack of interest. The whims and fashions of the public are noted by the commercial growers in deciding what to produce and this is true for obvious reasons. Why should they bother if there is no one to buy what they to have to sell! This deplorable situation may discourage prospective newcomers to the Echeveria hobby. But, on the other hand you can look at it in a different way. This is a rather unique hobby, and the adding of each new species can become a real thrill based on the very difficulty of finding the plant.


Seed-growing of the plants would be fine if pure strains of seed were on available anywhere, but today this is not easy to find, or does not exist. Field collected seed would be OK in regards to purity in most cases, but the hobby grower would probably have to try to go collect the seed himself. This is because today almost no one is doing this professionally! But for the hobby enthusiast to do this himself would translate into extreme difficulty, time required, danger and cost. It would mean actually going to remote, exotic locations. For some this may seem like a wonderful idea. Unfortunately, the habitats are mostly in Mexico, and now this country has new and strong laws and rules concerning all native species. This may not totally forbid seed gathering, but official permission and papers are required. European growers may be more likely to have available the rare species (plants and seed) for sale than any in America. One important warning must be made concerning seed. Never use seed collected from plants in a collection. The reason is that they are unlikely to be pure when many species bloom close together. If pure seed is to be grown, the plants must be carefully segregated for this purpose for a sufficient period of time.


The CSSA has a “seed depot” and ISI plants are offered from time to time, and this should be watched closely, as such offers are usually not repeated, and no offering last long. Echeverias can often be easily grown from detached leaves. If the leaf is healthy, each one can produce two sprouts by simply laying it on damp soil in low light for a few months. Probably no commercial seller will offer leaves, but they can easily be traded between private growers. Many species produce plenty of small plants that make excellent cuttings for propagation. Trading of cuttings, or of healthy leaves, with other hobby growers is a great idea, if enough contacts can be made. The making of “in person” visits to the several big succulent growers of Southern California is a good idea as the rarer types can sometimes be found there. But, if you do this, be sure to tell the manager that you are a serious collector and you want to see his special plants, or even this search will not be of much help as the rare plants are rarely put on public display.


The question may occur to some: is there any “complete Echeveria collection” anywhere in the world, such as in botanical gardens. The answer is: no, far from it. There is none now, and there has never been, and it is unlikely to ever happen. There are several species that no one has been able to obtain for growing in collections, and there seems little chance this problem will be solved.

 

MISCELLANEOUS


Chromosome counts for the various Echeveria species are quite varied, and polyploids are common. In he new Lexicon these counts are called the “cytology”. Kimnach includes the following remark in the new Lexicon regarding plants in this genus: “Cytology: extremely diverse in number of chromosomes, with every haploid number from n=12 through 34, and polyploidy numbers from 28 to 250”. There may be some relationship of these “chromosome numbers” to the various series to which each species may belong, but this relationship is not as direct as we might wish (and the concept of series its self is not yet complete and dependable). Some species have multiple sets of the same chromosomes, a condition known in botany as “polypolidity”. In all families of plants the “diploid” is the basic form, but similar-looking plants may have multiple sets of the same chromosomes in their genes. Poypolidity may or may not make the plant look different: there is no sure rule. A species with two sets of the diploid chromosomes is known as a “tetraploid”. That, and even higher multiples, are common in genus Echeveria. For some species in this genus the diploids have never been found in nature. It is assumed that at one time (in possibly ancient times) they did exist. In genus Echeveria it is odd that sometimes diploid (basic) counts may have lower actual numbers than tetraploids of some other species. Thus it is not possible to determine polidity by just knowing the actual count. But, it is often possible to separate diploids from tetraploids by observing certain behavior of chromosomes under the microscope using carefully chosen artificial hybrids intentionally created in the greenhouse. This is long and tedious work, and rather expensive too. Prof. Charles Uhl of Cornell U. has long been doing this kind of work, and has useful results published in many papers over the past several decades. These results help us in placing the Echeveria species into their proper series, thus proving which ones are, or are not really related. Walther and others did series placements in the past purely on the basis of observing (a subjective effort) from the physical appearance of the species (morphology); but this resulted it several errors. Recently Uhl has been able to correct several of these errors, and we are greatly indebted to him for that. As purely as a by-product of all of these hybrids being made, we also have some lovely hybrids to thank him for. He considered each of the many hybrids (that he had to make for his scientific work) on the basis of possible culture for beauty. He introduced the better ones to the trade through the years. Of course the vast majority of others had to be discarded as lacking sufficient merit.


The number of wild Echeveria species is now approaching 200, and there must be still a few more to be found. With so many species it is normal that there are several rare and endangered ones. Seed is not a recommended method of propagation unless rigid rules are carefully observed. This is because crossbreeding occurs so easily with the usual methods of growing. The result of such mixing is seed that will not come true to the mother plant’s species. The growing of seed is best left to the experts as it is very important to keep all species pure.


The natural range for the huge genus Echeveria is mostly within the borders of just one country: Mexico. One species spills over a bit into the USA (E. strictiflora in Texas). A few others are found in the highlands and mountains of Central America and on down the west side of South America (in the Andes Mts.) to as far south as Bolivia and Argentina. The more southern species fall into just a few series. More recently we are realizing that there are probably more kinds in western South America than we first thought, and new ones are still being reported.

 

Next: Echeveria vs Dudleya, sorting out the confusion.

 

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