A serious problem with the cultivation of Astilbe involves the incorrect naming of plants. It is a widespread problem both in the U.S.A as well as abroad. Henry Noblett, of the International Registrar for Astilbe, has made the most comprehensive attempt at properly naming and classifying Astilbe in his book "Astilbe: A Guide to the Identification of Cultivars and Common Species" 2008.
Based on a paper presnted by O.M. Paletiko in 1958, Noblett used the same approach by using a method of describing the panicle of the inflorescence as a basis for the records he collected and used the following criteria to aid in identification: (1) Color of the flowers (2) Height of the plant (3) Time of the flowering relative to others (4) Shape and composition of the panicle (5) Appearance of the terminal leaflet of the leaf (6) Diameter of the flower (7) Petal colour, shape and size (8) Color of the sepals, filaments and carpels and (9) Point where the sections of a leaf join together at the base.
Noblett states that five species of Astilbe have been used to produce the garden astilbes of modern times. To some extent some of their main characteristics persist but as time goes by and more are produced, it is becoming increasingly difficult to relate a cultivar to its original species. In fact, it is now thought to be better to list cultivars alphabetically rather than to divide them into their traditional groups as horticulturists have done in the past. The five species are A. japonica, A. chinensis, A. davidii, A. thunbergii and A. simplicifolia. There is some doubt as to whether a sixth, A. astilboides, is a species or a variation of two other species, A. japonic or A. thunbergii. It is nevertheless still a help occasionally, when identifying astilbes, to be able to recognize their main characteristics and to be able to relate them to the species which may have been involved in the production of the hybrid.