Description
Petrophytum – Petrophyton – Rock Spirea –
There are about 3 to 5 species of low spreading, often mat forming subshrubs in this genus. They occur in screes or rock crevices in mountainous of Western North America. They are grown for their short, dense, spike like racemes of tiny, fluffy, cup shaped flowers, each with 5 overlapping petals, borne from early summer to autumn, and for their neat, compact habit. They form dense mats or mounds of short, prostrate, branching shoots with densely packed, smooth edged, inversely lance to spoon shaped blue gray to gray green, leathery, hairy leaves. Grow in crevices in a rock garden or scree planting, or in a tufa, or in a trough.
Grow in poor to moderately fertile, humus enriched, sharply drained, preferably slightly alkaline soil in full sun.
P. cinerascens – This dense short stemmed subshrub from the Columbia River region of Washington State, USA, grows 24″ tall and 6″ wide. It has 1″ long gray green leaves with a sparse covering of hair. From mid summer to autumn it is smothered in 6″ wide heads of small white flowers.
Zones 6-9
