We are very fond of this spectacular small genus in Bignoniaceae with about 15 species distributed through eastern Asia. These are split into four subgenera, which have very different seeds. It is Subgenus Pteroscleris which is most familiar to gardeners. These are all herbaceous perennials with fleshy, tuberous rootstocks, distributed from Nepal and Tibet eastward to Yunnan and Sichuan in China. The other species are mainly woody-based perennials of varying stature and are essentially Central Asian in distribution, extending eastwards from Uzbekistan and Kazakhstan through the drier parts of the Himalayas to Southwest China and northwards to Mongolia and Manchuria. In general all members of the genus are intolerant of excess moisture, especially during winter, when they would naturally be under a substantial snow-cover. The members of Subgenus Pteroslceris, which come from areas with a high summer rainfall, are the most suitable ones in the open garden in Britain. Many have been most successfully grown in central and eastern Scotland, where the winters are colder and drier than in the West. The dwarfer species usually grow well in rock-garden or scree-bed conditions.

The genus has South American cousins in the equally spectacular genus Argylia from Chile and Argentina. We have listed seeds from some of these in the past but have failed to establish any in cultivation so cannot make any seed available at present. They are even more intolerant of excess moisture than the dry-climate members of Incarvillea.

Raising plants from seed is the only satisfactory method of propagation. It is usually recommended that seed should be sown in autumn but we have sometimes had quite rapid germination in mild weather and subsequent problems in overwintering young seedlings. We should advise delaying sowing until winter has set in. Germination will occur as the weather warms in spring and the seedlings should start flowering after 2-3 years if kept well fed. These are quite greedy plants.

Nomenclature : Andrew Grierson’s 1961 revision of the genus published in Notes from The Royal Botanic Garden Edinburgh is the basis for the modern nomenclature. The Chinese species in this genus are now covered in ‘Flora of China’, (online : http://flora.huh.harvard.edu:8080/flora ). This latter treatment does not wholly agree with recent British publications by Chris Grey-Wilson (see below), which are not only valuable botanically but by far the best source of information on this genus for gardeners. We follow the names in his accounts.

Further information : C. Grey-Wilson’s accounts are as follows : 'The New Plantsman' Vol. 1, Part 1, page 36 : "A Survey of Incarvillea in Cultivation" (March, 1994) and 'The New Plantsman' Vol. 5, Part 2, page 76 : "A new Look at Incarvillea Subgenus Pteroscleris" (June, 1998). There is also the note in ‘The Plantsman’, Vol.13, Part 4, p. 199 : “Incarvillea emodi” (March, 1992). A brief easily accessible reference is Phillips & Rix 'Perennials' Vol. 1, page 178, where a few species are illustrated.