Shrubs with white flowers come in all sizes and forms. Their blooms may be showy, modest, fragrant or odorless. What they have in common is a refreshing white-and-green color scheme that serves well as a backdrop for all other blooming plants. Many of them bloom in late summer to early fall, when other flowers are beginning to fade. Others are shade-lovers that brighten the darkest garden areas with their flowers.
Butterfly Bush 'White Ball'
Butterfly bush (Buddleja davidii) is a deciduous shrub hardy to USDA plant hardiness zone 5 with minimum winter temperatures of minus 20 degrees F and higher. The 'White Ball' butterfly bush cultivar, up to 5 feet high and wide, blooms reliably between July and September, and sometimes until frost with removal of its spent blooms. The fragrant, 4- to 10-inch spikes of white flowers are irresistible to butterflies, according to the Missouri Botanical Garden.
This insect- and disease-resistant shrub is most effective in groups. It's attractive in borders and butterfly gardens. For maximum flowering, plant it in full sun and average, well-drained soil. It suffers from prolonged wet conditions. Cutting the plants to the ground in late winter each year encourages vigorous growth and heavier bloom.
Sweet Pepperbush 'September Beauty'
Sweet pepperbush (Clethra alnifolia) tolerates winter temperatures as low as minus 40 degrees F. Standing up to 6 feet high and 4 feet wide, it has toothed, oval, deep-green leaves that become golden brown in the fall. 'September Beauty' is a pepperbush cultivar that blooms between the middle of August and late September. Its upright, cylindrical spikes of fragrant, bottlebrushlike flowers bring butterflies and bees to the garden. Brown seedpods often stay on the plants into the winter.
'September Beauty', according to the Missouri Botanical Garden, is a good choice for shade gardens where other shrubs struggle to bloom. Insect and disease free, it also makes a fragrant patio planting. Pepperbush likes moist or wet, acidic (pH below 7.0) soil and prefers partial shade to full sun.
Slender Deutzia 'Chardonnay Pearls'
Slender deutzia (Deutzia gracilis), a deciduous shrub native to Japan, is also hardy to zone 5. Belonging to the hydrangea family, it stands between 2 and 5 feet high and wide. The 'Chardonnay Pearls' deutzia has lance-shaped foliage that retains its lime green color all summer. In May, its abundant 3-inch clusters of pearl-white buds produce fragrant white blooms. Bell-shaped flowers are up to three quarters of an inch long. Plant groups of this shrub, recommends the Missouri Botanical Garden, in borders or as foundation plants. They also make an attractive hedge. The shrub performs best in full sun and moist, humus-rich, well-drained soil. Prune as soon as it finishes flowering.