ancient buildings - Chepstow Castle, for example - are made beautiful
in summer by this plant. It flourishes on old walls and is also
commonly found on sea cliffs, and in chalk pits. The main stem
is woody and perennial and it throws up a number of smooth branches
with greyish-green stalkless leaves. As a rule the flowers are
pink, but white and deep red forms are quite common. Each flower
is small, tubular, and ending in a long spur.