Several varieties of superior ornamental plants have been developed by the National Arboretum, and some are available for purchase from nurseries. This includes Diana, a rose of sharon (Hibiscus), Mohave, pyracantha and Allegheny and Catskill viburnums. The Arboretum is the international registration authority for cultivar names of viburnum and pyracantha, with Dr. Donald R. Egolf as registrar, appointed by the International Society of Horticultural Science.
Hibiscus Diana was introduced because of its waxy, heavy, dark green leaves and continues to bloom freely until autumn. The flowering will be heavier and the growth more compact if the plant is in full sun. Since the flowers are borne on the current season's growth, the plant responds than the more abundant ones of the unpruned plant.
Pyracantha Mohave was considered superior because of its frim, waxy, dark orange-red berries that ripen in mid-August, changing to red-orange as the season advances, and persist until midwinter. The folliage is heavy, dark green and semi-evergreen to evergreen, and the plant is resistant to fire blight and scab diseases.
Mohave gets to be about 13 1/2 feet tall and 16 feet wide. The plant wil grow in any good soil that has adequate drainage.
Full sun produces the best growth and heaviest fruiting, but the plant will thrive and bear berries to a lesser degree in partial shade.
Viburnum Allegheny has very dark green leathery leaves, is deciduous to semi-evergreen; has abundant inflorescences of yellow-white flowers in May and for several weeks in September and October; has brilliant red fruit, which as ripening advances turns black; and the plant has resistance to the bacterial leaf-spot disease. The plant gets to be 10 1/2 feet high and 11 feet wide.
Viburnum Catskill has compact growth, abundant inflorescences of creamy white flowers in May, dark red fruit ripening in mid-August and Persisting until midwinter, with good yellow, orange and red autumn coloration. The plant gets to be about 5 feet tall and 8 feet wide.