Worcestershire Record No. 3 November 1997 p. 6
The humble dandelions cause more problems of identification to botanists than most of the rest of the British flora put together. Even experts who confidently name the tiniest scrap of non-flowering vegetation in the field either lump them together as one aggregate or ignore them entirely. Within the flora project, we decided that we needed to do something about dandelions, but nobody involved had any knowledge of the genus Taraxacum. After some discussion, and rather more arm twisting, I drew the short straw and agreed to try to get to grips with the little devils.
I did not know what I was letting myself in for. I have since discovered that there are over 230 described species recorded in the British Isles, while the botanists who can identify them can be counted on the fingers of one hand. I started by getting hold of a photocopy of the then most recent book on the subject (John Richard's 1972 Taraxacum Flora), picking a few specimens at random, and trying to match them with the descriptions. This was singularly unsuccessful. Although I soon realised that dandelions covered a wide range of sizes, shapes and appearances, none of them gave a good fit to the descriptions I had.
The only hope left was the national referees. The following year I picked and carefully dried and pressed (or so I thought) several specimens and sent them off to John Richards and Andrew Dudman for expert determination. I eagerly awaited the return of my dandelions and the project's first positive results within the genus. At last the great day arrived, the postman brought a good sized parcel and I tore off the wrapping paper like a five year old with a birthday present.
The results were rather shaming. My beautiful specimens had been badly selected, poorly pressed and dried and most could not be identified. Returned with them was a helpful note on how to collect and prepare dandelions and a list of the currently accepted British dandelion flora. At least we had a few determinations but there was a problem. Most of the species identified were not mentioned in the 1972 flora so I had no descriptions to check against. The 132 species I knew about had turned into well over 200 (with quite a few of the 132 disappearing from the list).
Why are dandelions so difficult? There are two good reasons. The first reason is sex, or rather the lack of it. All our dandelions are apomictic, that is they do not require pollination for the seeds to grow. Thus every dandelion is a clone of its mother and every mutation potentially creates a new species. The dandelions we see around us today are probably the frozen remnants of an early episode of rampant hybridisation between sexual species which have since died out in Britain and some early apomictic species. So dandelions are difficult because there are an awful lot of them.
With apomictic species, differences may be small but should be consistent, and this is true of dandelions. If the seeds from one clock are grown under standard conditions then each resulting plant will be virtually identical. So identification should still be possible. This is where the second reason kicks in. Dandelions exhibit extreme phenotypic plasticity. Or to put it in English, they look totally different if grown under different conditions. Most characters, but especially leaf shape, change with age, nutrient levels, season, soil type, amount of sunlight, amount of water, and almost anything else you care to mention.
With tremendous help from John Richards and Andrew Dudman I have started to understand what to collect and have a good chance of a positive identification. Because of the seasonal variation, it is only worth collecting at the season of first flowering, certainly not after late May. Plants must be well grown but not too well grown. The drought stressed plant struggling to survive in the crack in the mortar of a wall, and the luxuriant giant from the top of the dung heap are equally atypical and will come back with "indet." written on them (or even "indet. - indifferent" as I have had)*. Because of the variation so characteristic of dandelions the specimen must be adequate. Two leaves and one badly pressed capitulum simply won't do.[*indet = indeterminate Ed].
Good drying and pressing are essential. Colour is often vital in identification and dandelions lose colour unless they are dried quickly, with frequent changes of drying paper. Bract size is important and more easily measured on fresh material, so field notes are helpful for this and such features as presence or absence of pollen and style colour. By taking more care with what I collect and how I prepare it I have improved my hit rate of identifications to around 75%.
Each year since, I have sent ever increasing numbers of dandelions to the referees. Many of these I have collected myself, but more recently other collectors have made significant contributions, especially Peter Garner, Terry Knight and Bill Thompson. The county total has risen year on year and 1997 saw a significant landmark as we reached 100 species for Worcestershire. Another recent landmark was the publication of the long awaited BSBI dandelion handbook by Dudman & Richards. I can at last pencil in my own tentative identifications before I send my specimens off to the authors. I even get some of them right now!
Where next? There is still a lot more to be done. Many species remain to be discovered - one of the 1997 additions was from my own garden! Even for the most collected species we have little knowledge of distribution. You can all help if you are willing. All you need to do is buy the new handbook, carefully read the sections on collection and preparation, gather in the harvest and pass them to me. I will get them identified if I think they are good enough to send off. You too can get a first County record!
|Dudman AA & Richards AJ (1997) Dandelions of Great Britain & Ireland. BSBI Handbook No 9. Botanical Society of the British Isles.
||Richards AJ (1972) The Taraxacum flora of the British Isles. Watsonia. Supplement to Vol 9 pages 1-141.
|WBRC Home||Worcs Record Listing by Issue||Worcs Record Listing by Subject|