Mid-summer heat causes drought over most of the island and much of the vegetation can appear parched when most naturalists visit Thásos. To see the flora at its best it is probably wise to visit as early in the spring as possible, otherwise it’s a case of hunting out the more promising habitats. The damp grasslands at Skala Potamias behind Golden Beach are a botanical treasure (though few now remain following rapid expansion of tourist development here) and other lush meadows can be found locally near Limenas (Thassos Town). Even a visit to the Agora in Thassos Town can be most rewarding before it gets cut towards the end of May. Otherwise, some of the richest botanical localities are found in the uplands, especially on the limestone pavements or below north-facing cliffs where the shade allows some of Thásos’s specialities to persist.
Whilst it can be difficult finding even basic information on invertebrates of the Greek islands, botanical investigations have a long tradition and as such there is an extensive body of literature to consult. Records from Thásos date back at least as far as 1816 (Flora Graecae Prodromus) but the earliest account of botanical exploration of the island is that of Grisebach (1841) in 1839, followed by Sintenis and Bornmüller in 1891. Probably the first substantial work to deal with the northern Aegean islands was Rechinger (1943) and this was followed shortly after by an account of the Thásos flora by two Bulgarian botanists, Stojanov & Kitanov (1945, 1946). Subsequently these workers produced a comprehensive review of the vegetation communities of the island (Stojanov & Kitanov 1950) - unfortunately in Bulgarian and an English translation would probably make fascinating reading!
In more recent years there has been a wealth of scholarly monographs, including Tutin et al (1964-1980), Davis et al (1965-1988) and Strid & Kit Tan (1997, 1998). What is striking from this progression of research is how many unresolved questions remain with respect to the flora of the Aegean and hence it can be difficult to state with any degree of certainty how many species of vascular plants have been recorded on Thásos. New discoveries continue to be made and Chilton (in Vladimirov et al 2009) reports 21 taxa newly-recorded for the island in the last decade. Chilton (2010) has produced an island checklist (updating an earlier version published in 1999), which builds on an earlier list for the vicinity of Skala Potamias published by the same author (Chilton 1997).
The Thásos checklist includes over 1500 taxa reported from the island, although about 66 of these are in need of confirmation or taxonomic verification. Chilton (2010) identifies six species and three sub-species endemic to Thásos (though Lotus aduncus included by Chilton is considered likely to be a red-flowered form of L. gebelia):
Cerastium decalvans ssp. glutinosum
Alyssum obtusifolium ssp. helioscopioides
Festuca cyllenica ssp. thasia
A further endemic sub-species has recently been recognised, Astragalus angustifolius ssp. odonianus (Brullo et al 2012), and in addition there are thirteen ‘near endemic’ taxa, confined to a limited geographical area which includes Thásos, such as Ranunculus thasius. As ever, I'm grateful to Lance Chilton for information on the island's flora.
Given the taxonomic uncertainties referred to above, it must be accepted that identification is not always straightforward. No field guide will allow the casual visitor to confidently identify everything they see, although there are many excellent guides available which will give an indication of the possibilities. These are too numerous to list in their entirety but some of the more popular are: Polunin (1980), Schönfelder & Schönfelder (1984), and Huxley & Taylor (1989). A photographic introduction to the Greek flora has recently appeared: Papiomytoglou, V. Wild flowers of Greece. Mediterraneo Editions.
Brullo, S., Giusso del Galdo, G. & Musarella, C. M. (2012). Taxonomic revision of Astragalus angustifolius group (Fabaceae). Bocconea 24: 19-52.
Chilton, L. (1997). Plant list for Skala Potamias. Marengo Publications.
Chilton, L. (2010). Plant list for Thasos. Marengo Publications.
Davis, P.H. et al. [Eds.] (1965-1988). Flora of Turkey and the east Aegean Islands. Vols 1-10. Edinburgh University Press.
Grisebach, A. 1841. Reise durch Rumelien und nach Brussa im Jahre 1839. Vandenhoeck und Ruprecht, Göttingen (2 vols.).
Huxley, A. & Taylor, W. (1989). Flowers of Greece and the Aegean. Hogarth Press, London.
Polunin, O. (1980). Flowers of Greece and the Balkans: a field guide. Oxford University Press.
Rechinger, K.H. (1943). Flora Aegea. Flora der Inseln und Halbinseln des Ägäischen Meeres. Akad. Wiss. Wein, Math.-Naturwiss. Kl., Denkschr., 105 (1).
Schönfelder, I. & Schönfelder, P. (1984). Collins photoguide to the wildflowers of the Mediterranean. Collins, London.
Sibthorp, J. & Smith, J.E. 1806-1816. Flora Graecae Prodromus. (2 vols.) Richard Taylor, London.
Stojanov, N. & Kitanov, B. (1945). Florata na ostrov Tasos. God. Sofijsk. Univ., 41: 233-320.
Stojanov, N. & Kitanov, B. (1946). Florata na ostrov Tasos. God. Sofijsk. Univ., 42: 89-196.
Stojanov, N. & Kitanov, B. (1950). Rastitelnit. otnošenija na ostrov Tasos. Izv. Bot. Inst. (Sofia), 1: 214-357.
Strid, A. & Kit Tan. [Eds.] (1997). Flora Hellenica. Vol. 1. Koeltz Scientific Books.
Strid, A. & Kit Tan. [Eds.] (1998). Flora and vegetation of North East Greece including Thasos and Samothraki. Botanical Institute, University of Copenhagen.
Tutin, T.G. et al [Eds.] (1964-1980). Flora Europaea. Vols 1-5. Cambridge University Press.
Vladimirov, V., Dane, F., Stevanović, V. & Tan, K. (2009). New floristic records in the Balkans: 12. Phytologia Balcanica, 15: 431-452.