This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Evergreen shrubs with alternate or rarely opposite petio-late leaves. Flowers small but numerous, in terminally thyrsoid cymes or panicles, blue, white or yellow. Fruit a 3-lobed drupe, splitting from the axis, and opening along the inner edge. Twenty-eight species have been described, all from North America, chiefly from the western coast. They are rather tender, and will only bear our winters in the south and west or against a wall. The name was applied to a spiny plant by the Greeks, but it is only applicable to some of the species of this genus.
1. C. azureus. - An erect hairy shrub. Leaves oblong, 3-nerved, serrulate, densely tomentose beneath, and often ferruginous in the wild specimens. Flowers small, blue, in lateral thyrsoid panicles. A native of Mexico, requiring protection.
2. G. Americanus. New Jersey Tea. - A small shrub with ovate-oblong 3-nerved serrate leaves, tomentose beneath. Flowers white, in dense clusters. G. ovatus has narrower glandular-serrate glabrous leaves and larger white flowers.
3. G. Veitchianus.- A very glabrous species with small oblong-obovate or oval serrate leaves and numerous dense clusters of bright blue flowers.
G. floribundus and G. Lobbianus are allied species with very hairy branches and leaves. Many other species have been introduced, but being rather tender are now only found in favoured localities.