Seventeen years ago, I attended my first Cherokee County Master Gardener Seminar — I read in The Tribune there was going to be a Hydrangea Seminar at the Hickory Flat Library and I could not wait to go — I had so many questions about my all-time favorite hydrangeas. Why were my pink hydrangeas blue after growing in my garden for three years?
Why weren’t my Pee-Gee hydrangeas blooming anymore and exactly when do you prune? I learned a lot. They were all colors, sizes, shapes, and more. I was overwhelmed and could not wait to get started planting new varieties.
Hydrangeas are divided into 5 main categories: Macrophylla, Arborescens, Quercifolia, Paniculata and Anomala. Macrophylla are the large, old fashioned blooms that most people are familiar with. There are 2 bloom styles — Mopheads and the Lace caps. Grown for their colorful blooms you can change or enhance bloom color via soil amendments. Most bloom early to mid-summer — lasting to late fall. They bloom on old wood, so timely pruning is a must.
Macrophylla are more prone to winter damage than other varieties—late winter freezes often nip the newly emerging buds so be prepared to protect. They prefer morning sun and afternoon shade, but they will tolerate more sun with lots more water. Proper planting, mulching, and vigilant watering is a must, especially when blooms are forming.
Soil pH determines whether Macrophylla blooms are blue or pink. Acidic – lower pH soils — result in blue flowers. To make them pink add lime to raise the soil pH. Higher pH soils – alkaline – result in pink blossoms. Add aluminum sulfate to make soil more acidic.
The Arborescens are the wild or smooth hydrangea that grow on new wood. Most of these Native — from New York through the mid-west to Southeast — wild hydrangeas are 4-6 feet tall. Arborescens tolerate more sunlight than the Macrophylla to produce plentiful blooms. They grow well in rich, moist soils that are high in organic matter. The blooms emerge as soft green, turn white, age to green, parchment and finally to brown. Deadheading will encourage re-blooming late in season. More pruning results in larger, but fewer blooms while less pruning results in more but smaller sized flowers.
Common Arborescens varieties are Annabelle and Grandiflora. Annabelle, 4 feet or more, are heavy bloomers, get floppy and can be pruned! Grandiflora, “hills of snow”, can grow to 6 feet tall and are not as heavy headed as Annabelle. The flowers have a flat underside held in 4 loose clumps and are greener and have larger blooms than Annabelle.
Quercifolia, or Oakleaf hydrangeas, have lobed leaves, grow 6-10 feet tall and bloom early summer into late fall. A four seasons of interest plant, it provides beautiful fall foliage (red tones) and exfoliating bark for winter interest. Oakleaf’s creamy white flowers bloom on old wood. Pruning is normally not necessary, but if desired, be sure to prune right after bloom. They need well-drained soil in a light shade location. They do not tolerate wet feet. Oakleaf’s are very tough and drought tolerant.
There are three main varieties of Quercifolia. “Snowflake” which produces huge fragrant flowers measure up to 18 inches. It is a vigorous grower with beautiful burgundy fall color. “Pee Wee” is the smallest, best for small spaces measuring four to seven feet tall. Fall foliage color is wine red. “Alice” measures 10 x 14 feet and has huge fragrant flower heads. It is the most sun-tolerant of all the Oakleafs. Excellent for fresh or dry blooms.
Paniculata hydrangeas will grow 10 — 15 feet tall and can be trained as a tree. It produces large white 10- 15 inches long cone shaped flowers. In autumn, the flowers fade to pink and bronze. Paniculatas are excellent hydrangeas to dry—pick late in the season and hang to dry. Paniculatas can do well in full sun. Blooming on new growth, they can be pruned severely and are good to use in perennial beds; Common varieties are Tardiva and Floribunda.
Anomala is a climbing hydrangea that can grow up to 60 feet in height. It has two-to-four-inch heart shaped leaves that surround scented June and July blooming white flowers. It also has peeling, cinnamon colored bark that is attractive in winter. Anomala hydrangeas tolerates full sun and partial shade. It grows best in moist, well-drained soil, high in organic matter. Allow 2 years to get established, and up to 4 years to start blooming,
To fertilize hydrangeas, apply a slow-release balanced fertilizer two or three times a year (March, May and August). The amount of fertilizer to use varies with plant size. Better to under fertilize than overfertilize. Hydrangeas normally do not need annual pruning. Reasons to prune include to remove dead stems and tips, crowded stems and to reduce size or reshape. Prune hydrangea types that bloom on old wood before August 1. Arborescens and Paniculatas bloom on new wood. prune hydrangea types that bloom on new wood winter or spring. Do not prune immediately before blooming. Happy Gardening!