Mountain Hydrangea (Hydrangea serrata)
Typically more cold-hardy than Hydrangea macrophylla, but with smaller, mostly lacecap flowers, Hydrangea serrata has been catching on in American gardens. This species from Japan and Korea isn’t as showy as the Bigleaf mopheads, but they are subject to color change based on soil pH and aluminum content in the soil. They also produce flower buds on side stems as well as the end of the main stems, providing a continual source of color. Hardy from Zones 6-9 (often hardy in Zone 5), it rarely grows taller than four feet. Varieties that I favor:
- ‘Blue Billow’ rarely misses a step in my garden, regardless of winter temperatures. It grows, at most, four feet tall, and the leaves have good red color in the fall.
- The Japanese name, ‘Schichidanka’ is worth learning to pronounce. Its delicate look belies its hardiness, as it has bloomed for the past 16 years in my garden. Its height is perfect (around four feet tall) for close-up viewing of its double lacecap flowers.
- ‘Tiny Tuff Stuff’ is a new variety that reaches just two feet tall and has doubled lacecap flowers. It’s just come through a tough winter seasons yet, and already has flower buds.
Besides the two species that have blue to pink potential, listed below are three others that are worthy of attention for their beauty and no-fuss culture.
Smooth Hydrangea or Annabelle Hydrangea (Hydrangea arborescens)
This American native hydrangea has either lacecap or mophead flowers whose colors cannot be changed. The best new varieties have a more compact stature and stronger stems. Some boast flowers as big as your head, and a few even sport pink flowers.
Hydrangea Arborescens are hardy in Zones 3 -9, prefer full sun to partial shade, and bloom on the current year’s stems. It has fluffy white-flowers and is icon of high summer that goes into a droop after a few rainstorms.
To encourage strong, new growth, and lots of flowers, prune back by one-third its total height in early spring.
- Hydrangea ‘Incrediball’ is true to its name, although it’s best to stake this five-footer, or even surround it with a four-foot wire fence before the stems emerge each spring.
- Hydrangea ‘Invincebelle Mini Mauvette’ has blossoms of the deepest pink. It’s compact, reaching just three to four feet tall, and produces flowers all summer.
- Hydrangea ‘Lime Rickey’. Instead of the fully-round blossoms, ‘Lime Rickey’ has large, disc-like blooms (like the top half of a mophead) that start out a fresh green color and age to rich jade, all accented with pink pollen for a unique accent. It grows up to five feet tall and wide.