Smooth Hydrangeas– Hydrangea arborescens
Description: Smooth hydrangeas are native to the eastern United States, and are usually found in wooded areas. They are Cold Hardy in Zones 3-9, so they can tolerate our winters here in Wisconsin. This hydrangea can tolerate low- light conditions because they prefer morning sun and shade during the afternoon. As long as they get 4-6 hours of sun they will do great. The more sun you give them, the more blooms they will produce. Smooth Hydrangeas are unique because they spread through rhizomes in the soil and create masses. The branches are not woody like a Panicle Hydrangea, but a softer more brittle structure. The plant structure is different from other hydrangeas because it produces new shoots every year. Because of the new shoots, you can cut the entire plant down to the ground every year. The plant blooms on new wood every year, so it is best to rejuvenate the entire plant to produce the best blossoms. You can leave portions of last years’ growth, but it will not benefit the plant. The only Smooth Hydrangea that used to be available as a white mophead flower called ‘Annabelle’, that grows to about 4 feet wide and tall. Through time, breeders have developed new cultivars that display different flower colors and smaller sizes. The newest additions are the Invincibelle series of Smooth Hydrangeas that only get 2-3 feet tall and wide at maximum. These are tough plants that don’t require a lot of maintenance. You do not have to fertilize this type of hydrangea to influence its coloring.
Examples: Annabelle, Incredi-Ball, Incredi-Ball Blush, Invicibelle Wee White, Invincibelle Ruby, Invincibelle Mini Mauvette, Invincibelle Limetta, Invincibelle Spirit
Panicle Hydrangeas– Hydrangea paniculata
Description: Panicle Hydrangeas are native to China and Japan, and have been bread throughout time to create desirable growth habits and flower characteristics. They are Cold Hardy in Zones 3-8, so they can tolerate our winters here in Wisconsin. They can 3 to 10 feet tall depending on the variety you choose. Panicle Hydrangeas require sunlight in order to flower. They prefer full sun, but if you can provide morning sun and afternoon shade that should be enough sun exposure for blossoming. Panicle Hydrangea flowers are larger and more rigid than other hydrangeas because of their woody habit. Most of the flowers are cone-shaped or open panicle heads that start to blossom in different shades of white that turn to different shades of pink in the fall. The elements in the soil do not influence the color of the flower, but change in temperature triggers their flowers to change colors. Panicle hydrangea flowers are tough enough to make it through the winter to give your garden interest in the snow. If you want to dry the flowers for decorative use, prune the flowers in fall and let them dry. The flowers will brown slightly, but may retain some of the pink color. It is best to prune Panicle Hydrangeas in the spring because it is easier to see where new buds are emerging. Our winters may cause the branches to naturally die back, so you don’t want to open wounds in the fall that may dry out in the winter. Woody hydrangeas bloom on new wood, so cutting at least 1/3 of old-growth off of the shrub would benefit this season’s flowering. This landscape staple does not require a lot of maintenance, just a little pruning in the spring will bring you interest year-round.
Examples: BoBo, Limelight, Little Lime, Little Quickfire, Pinky Winky, Quickfire, Strawberry Sundae and Vanilla Strawberry
Bigleaf Hydrangeas– Hydrangea macrophylla
Description: Bigleaf Hydrangeas are native to Japan and have been bred to be desirable landscape plants for Cold Hardiness Zones. Bigleaf Hydrangeas prefer morning sun and afternoon shade. They do not like the hot afternoon sun exposure. Flower buds are set in late summer, so if you do any fall pruning on the shrubs, you will cut off forming flower buds starting around August 1st. It is best to prune Bigleaf Hydrangeas after their blossoms start to dry out. At this time, you can do any shaping or rejuvenation pruning for better branching. Because the flower buds are set in fall, you will want to protect the shrub during the winter with mulch or boughs, so the flower buds do not freeze or get damaged. In the spring, you may have natural dieback. Once the buds start to emerge, you can prune the stems back to the living buds. There will be a woody portion of the plant near the base and the rest of the growth will be succulent new growth each year. The large leaves will emerge in late spring to avoid any risk of frost. Once the leaves emerge, the plants will begin to bloom in shades of pink, blue and purple. The blossoms resemble large snowballs and lace caps. Bigleaf Hydrangea flowers change color with changes in soil pH. Blue-purple color is encouraged by aluminum particles in the soil or acidity. Pinks are encouraged with alkaline soils. You can manipulate your soil pH by treating the soil in the area near the shrub. These hydrangeas bring a lot of interest and a unique color to the garden.
Examples: Endless Summer, Bloomstruck, Blushing Bride, Summer Crush, and Twist ‘n Shout