Best grown in loose, medium moisture, well-drained soils in full sun. Plant in sheltered locations north of USDA Zone 7. In USDA Zones 5 and 6, this shrub often suffers winter dieback or dies to the ground. It is not considered reliably winter hardy throughout USDA Zone 5. Even though plants may die to the ground in Zone 5-6 winters, the roots often survive the winter and push up as much a 4-7' of new growth the following year. Because flowering appears on new growth, winter dieback or pruning back to the ground will not affect flowering. In the St. Louis area, this shrub is often regularly pruned close to the ground in early spring each year in somewhat the same manner as is also usually done with crape myrtles.
'Colonial Blue' is a chaste tree cultivar that is typically grown in warm winter climates as a vase-shaped, deciduous shrub (to 10-15' tall) or sometimes trained as a single trunk tree. In cold winter areas in USDA Zones 5 and 6, it is more often cut back each year and grown as a 4-7' tall woody perennial shrub. Features aromatic, compound, palmate, grayish-green leaves with 5-7 lance-shaped leaflets (each leaflet to 6" long) and tiny, fragrant, colonial-blue flowers appearing in loose panicles (to 12" long) throughout the summer. Flowers are quite attractive to butterflies and bees.
No serious insect or disease problems. Leaf spot and root rot are occasional problems. Winter hardiness in the St. Louis area is a concern.
Interesting foliage and late summer flowers. Shrub borders, foundations, cottage gardens or butterfly gardens.