Abstract
The Indonesian Island of Sulawesi is home to a number of members of the ginger family, Zingiberaceae, with unusual turquoise flowers not found anywhere else. A recent paper reinstating Hellwigia, using molecular evidence, placed these "jade gingers" in this genus. During a joint expedition between the Royal Botanic Garden Edinburgh and Bogor Botanical Gardens 26 years ago, an interesting jade ginger was collected at Mt. Sojol. This is similar to two other named species from Sulawesi, H. coeruleoviridis and H. glacicaerulea, in having unusual dimorphic, turquoise-bluish green flowers but differs from both in the much shorter ligule without a demarcation line and is described here as Hellwigia opalina. In preparation for this, all available material of jade gingers from Sulawesi was examined, and all except the collections from Mt. Sojol had a long ligule with a demarcation line similar to H. coeruleoviridis and H. glacicaerulea. It is, however, questionable whether the identification by R.M. Smith of several collections from Lore Lindu National Park, Central Sulawesi, matches the type of H. coeruleoviridis, which was lost in Berlin during the Second World War. Until this species has been recollected at its type locality, here identified as Mt. Tentolomatinan, 300 km away, the identification cannot be easily ascertained. Rhizomes from Mt. Sojol were cultivated in botanic gardens, and plants cultivated at the Royal Botanic Garden flowered several times, which enabled detailed studies and dissection of both flower morphs. This is usually impossible during fieldwork and emphasizes the importance of cultivation of gingers-not just for ex situ conservation but also for research purposes. Detailed photographs taken of the cultivated plants were used to obtain a better morphological understanding and to illustrate Hellwigia opalina in the present paper.