Sorbus is essentially a genus of large shrubs and small trees which falls into two groups. The whitebeams have more or less entire leaves which are often silvery or white-backed and they can have attractive panicles of creamy flowers, but in general the berries are not an important feature in this group. The other group, the rowans are characterised by pinnate leaves which often turn an attractive yellow, orange or red in autumn, and the berries can be white, cream, yellow, orange, pink or red, often changing colour as the season progresses. Most of the species in this group originate in western China (although our own rowan S. aucuparia is of course a native) and they have become very popular in recent years, so that more than 20 species and varieties are now readily available. Many are apomictic, setting berries and seeds without fertilisation, so that berry-set is automatic, and seedlings tend to be identical to the mother.
Although many of the rowans are suitable for the small garden and form an excellent background to the rock garden, only two are small enough to actually inhabit the rock garden. One of these, the very dwarf S. poteriifolia has tiny pink flowers and white berries. However it is unreliable in the garden, tending only to thrive in Scotland and the far north of England and disliking hot dry summers. A cool trough with a well-drained woodsy mix is perhaps the best recipe for this tricky customer, if you can obtain it!
Although it also originates on the high mountains of the Tibetan border (I have seen it on the slopes of the Bai Ma Shan) S. reducta is a much more reliable subject and thrives in most garden conditions which are not too hot and dry. Unlike the tiny S. poteriifolia, most forms reach an ultimate height of about 60 cm, with a spread in the non-suckering form perhaps twice this. The off-white flowers are produced in June and are not particularly attractive, but the abundantly produced berries start to colour pink in August and by September they have usually reached their final intense day-glow pink. They are not very popular with birds, so that the berries usually last long after the leaves fall, often making a show well into December.
A final warning. Many of the plants now available are of the non-suckering form, and unless you want a plant which emerges metres away from the parent in the midst of your favourite plant, this is the one to go for. It does sometimes produce very short suckers, but these are rarely a problem. Avoid the suckering form at all costs!