It’s no secret that the Cape and Islands have a longstanding love for hydrangeas.
From Bourne to Provincetown, they grace our fences and line our foundations. We write poems and books about them. We celebrate them with their own festival, and when the summer season draws to a close, we cut and dry them to admire during our long winters.
In summer, I especially love browsing our local garden centers to seek out new cultivars of hydrangeas. The colors range from white and pink to red, purple and blue. Some are as small as two feet tall, while others can grow to eight feet or more, not to mention a climber that can grow to more than 20 feet! Some flower on old wood only, some on new, and some flower on both; it’s easy to get overwhelmed. How do you choose?
To help select the best hydrangeas for your site conditions, here is a look at six of the most common species. I recommend assessing your home’s site conditions, including sun and shade, water availability, type of soil and pH level.
The most popular of the hydrangea species, Hydrangea macrophylla or bigleaf hydrangea is often noted for its sensitivity to soil pH, with acidic soils delivering degrees of blue flowers and alkaline soils producing pinks. What the plant is really reacting to is the availability of aluminum in your soil, which is determined by its pH level. For the bluest blooms, your soil’s pH level should be between 5.2 to 5.5. At levels over 6.0, your plant won’t be able to absorb the aluminum in soil, resulting in lovely pink to mauve blooms. Not all bigleaf hydrangea cultivars are pH sensitive; some produce lovely white flowers at any pH level.
As we often see on the Cape, flower buds are susceptible to freezing from late frosts. Avoid placing these on a south-facing wall where radiant warmth can encourage early budding, leaving them vulnerable to frost.
New cultivars crop up continuously. Most notable are the remontant varieties that bloom on current-year stems as well
as previous-year wood, such as “Endless Summer.”
Dwarf forms of bigleaf hydrangeas such as the “Cityline” and the “Let’s Dance” series are also growing in popularity.
These plants range in height from 1 foot to 4 feet. Don’t be fooled though; there’s nothing dwarf about the size of the blooms!
A native to Japan, H. macrophylla prefers partial to full shade, with the best blooms occurring with some sun.
Originating in Korea and Japan, Hydrangea serrata or “Mountain Hydrangea” greatly resembles H. macrophylla, though it may have less cold tolerance. Most cultivars are of the lace-cap form. Look for “Coerulea Lace,” “Benigaku” and “Blue Billow.”
A native to China and the Himalayas, Hydrangea anomala or “Climbing Hydrangea” is a true climbing vine using rootlike holdfasts to grasp onto vertical surfaces, fences or posts. These can be stunning growing on a north-facing chimney or wall. It is important to note that once you remove the vine from a wall, its holdfasts will never cling again. You’ll need to prune back the plant and allow it to regrow. Its sweet-smelling flowers show best in mid-summer. Tolerant of sun to partial shade conditions, H. anomala can also tolerate a wide range of soil conditions.
Hydrangea paniculata, aka “Panicle Hydrangea,” really shines in the fall landscape. Grown either as a single-stemmed tree-like specimen or in its natural shrub shape, this species has taken its rightly deserved place in Cape Cod gardens. A native of China and Japan, H. paniculata is perfect for sunny locations, but will take some shade as well. Although it seems to be somewhat drought tolerant, it does best in moist, well-drained soils. Most cultivars have a distinctive cone-shaped inflorescence, sometimes turning shades of pink to red as the season progresses. My favorites include “Limelight,” “Strawberry Sundae” and “Fire Light.” Look also for dwarf forms like “Little Lime” and “Bobo.”
Hydrangea arborescens, or smooth-leaf hydrangea, is best known for its cultivar “Annabelle,” whose large mophead flowers can visually light up a shaded spot in a garden. Flowers are borne on new growth, so they are all but guaranteed to bloom each year. Native to southern New England, H. arborescens prefers partial shade and a moist, well-drained, organically rich soil. Check out cultivars “Incrediball” and “Invincibelle” varieties and “Hayes Starburst.”
Native to the southeastern United States, Hydrangea quercifolia or oakleaf hydrangea is especially prized for its beautiful autumn foliage turning shades of red to purple. Best leaf coloration occurs when sited in some sun, but this species does well in partial shade. Plant in moist, well-drained, organic soil. Upright pyramidal flowers peak in July. Notable cultivars include “Alice” and “Snow Queen.”
About the author: Barbara is the owner of Gardens by Barbara Conolly, Inc., a design, installation and management firm that serves clients throughout the Cape and South Shore. She is a graduate of Cornell University, a Massachusetts Certified Landscape Professional, an International Society of Arboriculture Certified Arborist and a lifetime member of Pi Alpha Xi, the National Horticulture Honorary.