The World of Haworthias
It was in 1965 that my interest in succulents was awakenend and from the very beginning
I had a special liking for succulent lilies. My serious interest in Haworthia did not
start until 1983 when I began building up a comprehensive Haworthia collection. By the
end of my college days, and the start of my professional life in another town, it became
obvious that I could no longer keen my succulent collection at my parents' home.
My new dwelling included a small conservatory which received only the morning sunlight and this was the main reason why I chose those succulents which do well without strong light. Small wonder, then, that Haworthias became my first choice.
By chance, I received nearly 50 different Haworthia offsets as a gift from the Botanical Gardens in Bonn. This was a further encouragement for me to pursue the genus Haworthia. My next step was to obtain more literature and information so that I could achieve a better understanding of the subject.
The Lexicon of Succulent Plants by H. Jacobsen contained numerous brief descriptions of Haworthias but I found these difficult to match in order to classify my own plant material.
I had great expectations for M.B. Bayer's Haworthia book, published in 1982. In this book he reduced the abundant number of Haworthia names, supporting his findings with constructive and convincing explanations. The excellent photographs helped to remove doubts in making comparisons with my own plants but, nevertheless, I had now become even more curious and wanted to extend my knowledge further.
The Haworthia book from J. Pilbeam, published in 1983, had many excellent pictures and contained some new names. These names referred to ± remarkable forms being of special interest to collectors. Accordingly in my opinion they are not very helpful towards a better understanding of the genus.
The book from C.L. Scott, published in 1985, confused many Haworthia collectors because he presented a rather different classification to that of Bayer. Scott did not accept the three subgenera erected by Uitewaal and used by Bayer. The detailed descriptions, supported by photographs and distribution maps, corresponded with existing plants available in cultivation, but I could not agree with most of Scott's opinions.
However, these three books could not give me satisfactory answers to all of my questions and this situation was the inspiration for my own investigations. Starting in 1989, I decided to collect and analyse all available references published on haworthias. This book is the culmination of my preliminary findings.
About this bookThis volume is not a casual read on the subject of Haworthia or a monograph of the genus but a "working" book with a great deal of data and brief explanations which should allow the reader to obtain desired information about the genus for himself. How to obtain information is described at the beginning of each chapter, where the reference-numbers will lead to the respective data sources.
My studies relate to 968 references. The result of this work produced about 10,000 literature references for the genus Haworthia.
The analyses were checked several times as the project developed and I can guarantee that all documentation references have been done with great care. Nevertheless, the possibility of mistakes cannot be excluded and any advice or correction would be appreciated.
The analysis of references takes into consideration only "true" haworthias and their effective or validly published names, as well as the names of their basionyms and synonyms. All taxa presently accepted as belonging to other genera - for example Aloe, Astroloba, Chortolirion, Gasteria and Poellnitzia - are not included.
As a rule, no literature references are given for a hint on cultivation, a caption or a simple mention of a name. Not considered is the treatment of haworthias in most collector's books.
My intensive work with available literature, specimen plants and discussions with other Haworthia experts has given me an insight into how the taxa could be classified and defined. In this book my preliminary conclusions are described as a working hypothesis. The taxa which in my opinion are different from those held by Bayer  are cited at the beginning of chapter 4.
Future ProspectsIn order to proof my working hypothesis detailed field studies are necessary to obtain a better understanding of the variation within every single taxon.
The result of these studies will be described in a further volume of my work on haworthias. In addition, I would also like to study carefully the importance of morphological characters both in nature and in the greenhouse. This should allow predicative descriptions and proof of the correctness of my working hypothesis.
Studying the morphological characters of haworthias will take some time but I will prepare the second volume for publishing, with all available descriptions of the taxa, as quickly as possible.
Any support towards the Haworthia-Project would be gratefully received; especially that of supplying me with copies of missing references or donating authentic plant material.