Sorbus rupicola


Sorbus rupicola, known as rock whitebeam, is a rare shrub or small tree best known from the British Isles but also reported from Norway, Sweden and Russia.
It can reach heights of 10 m. It grows in rocky woodland, scrub and cliffs, usually on limestone.
The species reproduces apomictically and was presumably created by autopolyploidysation of the common whitebeam proper. It contains a tetraploidal set of chromosomes.
Sorbus rupicola is a member of Sorbus aria agg., which contains 20 subspecies. A key to this aggregate is given in Stace - though be warned Stace states "It is probably impossible to construct a reliable key to the agg."! Stace gives Sorbus rupicola the following characteristics: