Some are quite hardy and have flowered in zone 8 in Washington and other areas. Among those that have done well are C. salignus , C. subulatus , C. viridiflorus and C. violaceous . C. pallidus , C. pityoides , C. rigidus , C. teretifolius , and perhaps C. viminalis are also good ones to experiment with, as well as cultivars such as 'Woodlanders hardy'. Most are shrubby, but a few can reach small tree proportions if trained. See this site for more information about these plants.
Grevilleas grow throughout Australia and range in size from small shrubs to large trees.
They are also in the Proteaceae family, and produce very interesting showy flowers. Most are easily grown from seed or cuttings. In general, they are characterized by small leaves and flowers, and they vary in size from small shrubs to medium-sized trees. Though the flowers are small, they can often be remarkably profuse and showy. Some species grow in areas natively subjected to considerable amounts of snow, and are very likely to prove hardy here.