White spikes of Clethra alnifolia; photo courtesy of Flickr cc/Katja Schulz
Here are just a few of the trees and shrubs that can be planted for summer interest in the northeastern United States. The month of interest may vary from year to year with environmental conditions.
July:
BOTANICAL NAME
COMMON NAME
Abelia x grandiflora
glossy abelia
Albizia julibrissin
hardy mimosa
Buddleja spp. and vars.
butterfly bush
Callicarpa japonica
Japanese beautyberry
Clethra alnifolia
summersweet
Hydrangea spp. and vars.
hydrangea
Hypericum spp. and vars.
St. John's wort
Koelreuteria paniculata
golden rain tree
Magnolia grandiflora
southern magnolia
Oxydendrum arboreum
sourwood
Stewartia pseudocamellia
Japanese stewartia
Symphocarpos spp.
common snowberry
Tillia spp.
linden
The delicate white flowers of Oxydendrum arboretum (sourwood); photo by Ivo Vermeulen
The Creative Shrub Garden by 
Hydrangeas for American Gardens by 