The second week of September is when autumn color starts to peek through the summer green, and hydrangeas may be the most spectacular flowering shrub in the landscape.
In my own garden I have created a hydrangea “room” hidden behind a hedge with walls made from all the different types of hydrangeas that grow so well in Western Washington. (You can see more of the hydrangea room plus pruning videos about hydrangeas on my YouTube gardening videos. )
In honor of the heavenly hydrangeas that thrive in our climate and the new hydrangea varieties now available, here are the most-asked questions about hydrangea growing in Western Washington.
Q. Do hydrangeas like sun or shade?
A. That depends. The big leaf or mophead Hydrangea macrophylla (old fashioned round ball blooms of blue flowers) needs shade from the hot afternoon sun to prevent wilting. The hydrangeas with pointed blooms or Hydrangea paniculata (Pee Gee hydrangeas) flower best in the sun. A location with morning sun and afternoon shade is ideal for most hydrangea varieties.
Q. Are there any hydrangeas that stay small and compact?
A. Yes! The sun-loving “Bobo” is a dwarf white hydrangea with pointed blooms that grows to four feet. There also are the cold hardy mountain hydrangeas, such as “Tuff Stuff,” and the pink, pointed blooms of “Little Quick Fire” on dwarf plants.
Also look for the dwarf limelight hydrangea ‘Little Lime’ and the series of Cityline hydrangeas, such as Rio, that do great in large containers with tons of blooms on compact shrubs.
Check in with your local nursery as there are new dwarf shrubs being introduced every year. A full service nursery can order plants for you. Keep in mind that even dwarf shrubs can reach to 6 feet if given ideal growing conditions.
Q. When and how do I prune my hydrangeas?
A. Well that depends. In general most hydrangeas bloom best with no to little pruning. Plus you should wait and prune in the spring, not in the fall.
Harvesting the flowers now is a great form of pruning as most of the old fashioned hydrangeas flower on 2-year-old branches, so pruning back the blooming branches in fall will naturally shorten branches that will not flower next summer. But you can prune to shape most hydrangeas in the summer.
Q. How does one change the color of hydrangeas?
A. Some hydrangeas will turn blue in acid soil and pink in soil that is neutral. Our soil is naturally acid from the heavy rainfall in Western Washington, so most are blue.
You can add lime around the base of your hydrangeas now, and next spring they will be pink. Or grow them in potting soil, and they will turn to pink as most potting soils are basic. I like to put lime around just half the hydrangea. Then you get purple blooms in the middle of the shrub, with pink on one side and blue on the other.
White hydrangeas stay white. The pointy blooms of the sun loving Hydrangea paniculatas fade from cream to pink, and the color cannot be changed by the pH of the soil.
Q. When can I transplant a hydrangea?
A. Anytime the ground is not frozen is okay to move a hardy hydrangea. Just remember these are shrubs that love moist soil, so add some compost to amend the planting soil, mulch on top of the roots to seal in moisture and give plenty of liquids after the transplant operation.
▪ Saturday, Sept. 14, 10 a.m., Windmill Gardens, Sumner, “Smart Gardening Ideas for Fall.” Free but must register at 253-863-5843.