I’ve started my spring visits to garden centers and nurseries.
Across most I have noticed the selection of hydrangeas is enormous. Such a big change from the handful available when I first started working in horticulture 30 years ago.
Very few of the mophead or bigleaf Hydrangea macrophylla were sold — and these were not reliable bloomers unless you happened to have a very protected site or lived in a Zone 6 microclimate.
Hydrangea macrophylla is root hardy to our area’s USDA hardiness Zone 5, but the flower buds are only hardy to zone 6 or 7. Because the buds form in summer for the following season, they are almost always lost over the winter. The typical result is a big, leafy shrub that rarely blooms.
This all changed several years ago, with the hybridizer’s development of reblooming varieties. Flower buds remain vulnerable to winter cold, but plants also form new buds on their new growth, allowing them to bloom even if the all the old branches die to the ground.
Endless Summer hydrangea was the first, with blue or pink mopheads — a nearly round cluster of showy sterile flowers.
This success was quickly followed by sister plants in what has become the Endless Summer series. Blushing Bride sports white mopheads kissed with pink or blue. Twist-n-Shout is unique with lacecap flowers, clusters of deep pink centers (fertile flowers) surrounded by a ring of large, open (sterile) flowers. BloomStruck features sturdy red stems and big mophead flowers in purple or rose-pink. New for 2019 is Summer Crush, with big raspberry red or neon purple blooms.
Other shrub breeders have jumped on the bandwagon, introducing their own varieties with this reliable blooming quality. Forever and Ever series offers several varieties of mophead or lace cap flowers, some with two-tone petals. Let’s Dance series has five mophead varieties and Tuff Stuff with blue, purple or pink lacecap flowers, all from Proven Winners.
Double Delights series from Monrovia has double the petals on the sterile florets, in several colors and both mophead and lacecap forms. Next Generation series offers several uniquely colored mophead varieties.
Varieties advertised as having a range of colors will vary based on the soil pH and the presence of aluminum. An acidic soil with a pH of 5.0-5.5 is optimal for blue to purple flowers, and 6.0-6.5 for pink to red flowers. 7.0 is neutral on the pH scale. Note that the pH alone will not affect the flower colors, there must be aluminum present — so the best soil amendment is aluminum sulfate.
Two other species of hydrangeas are more broadly adapted to our climate, and we can successfully grow any variety offered.
Smooth hydrangea (Hydrangea arborescens) is hardy to zone 4, and the most familiar selection is Annabelle with very large mophead clusters of snow-white sterile flowers. Newer varieties offer strong stems that don’t bow under the weight of the heavy clusters. Bella Anna and the Invincibelle series are breakthrough introductions with true pink flowers.
Panicle hydrangea (Hydrangea paniculata) is just as hardy, with cone-shaped flower clusters. The old standard, PeeGee (paniculata grandiflora) has dense sterile flowers that form a solid cone. Later blooming Tardiva has a more open cluster.
Limelight is the current best of the white forms, with clusters emerging lime green, gradually turning white and tinting pink with maturity. Most striking is its constant flowering, resulting in green, white and pink on the same plant as the season draws to a close.
More pink-flowering forms are offered in this group, though all age to pink, rather than starting that way.
The species can grow quite large, and plants can be pruned hard in spring to keep them smaller, or simply choose one of the many compact varieties.
Make your best hydrangea selections by understanding the options.