Earlier this year – and in the midst of stay-at-home orders – we were in the garden to the south of the house, cutting back all sorts of brush. Mostly blackberries and salal, but there were also bindweeds, chocolate vine that had gotten out of hand, and a few unidentifiable shrubby plants. Imagine our delight when we cleared enough to find about a dozen beautiful blue flower clusters of a big-leaf hydrangea, blooming away. This was not a plant I had planted and forgotten, but instead an “escapee,” no doubt planted by the birds or perhaps one that just slowly crept about 10 feet from a hydrangea I had planted. This one was from a cutting from gardening friend Mary who moved away many years ago. And here was a “daughter” from that original plant. And the best part was it was so happy and in such a good spot that we didn’t need to move it but could let it thrive where it was.
Hydrangeas are one of the most popular flowering plants for the coast. For one, they are easy to grow, and secondly, they are a beautiful plant. There are several different varieties and each one has its own charms. There is even a climbing variety (Hydrangea anomala petiolaris) if you need some height in your garden.
They mostly like partial shade or full sun in our not-too-hot summers. In hotter areas, they will prefer shade to avoid leaf and flower scorch. Well-drained, moist and humus-rich soil is preferred by most varieties. There is a variety for each use in the garden: back of the border, as a shrub border, planted in groups or as specimen plants, or even in large containers. The climbing varieties can be trained up a wall or an arbor, or even across a pergola.
The most common is Hydrangea macrophylla, the big-leaf type. This plant has a rounded or mounding shape and can grow to 6 feet tall and 8 feet wide. Their flowers can grow either as a mophead or a “lace-cap,” depending on the variety. Lace-cap flowers look just like the little lace caps that women of the 18th century wore perched on the top of their heads. When you see a lace-cap, you will immediately recognize it as looking nothing like the mophead types.
Another favorite is the oak-leaf hydrangea (H. quercifolia), named for obvious reasons: the leaves are shaped like those of an oak tree. These form flower clusters that are cone-shaped and will bloom in late spring or early summer. Most of these have white flowers that turn to pinkish-purple as they age. This plant is nice because the “oak leaf” will turn bronze in the fall, giving some fall color to that part of the garden.
Some of the hydrangea varieties can have their flower color affected by the pH of the soil. Traditionally, the way to get them to present their best colors was to fertilize with acidic formulas (as for azaleas and rhododendron) for the deep blues, and fertilize with alkaline formulas (lime, wood ash, bone meal) for pink flowers. You can change the colors from year to year by changing the acidity of the soil. But beware: it may take a season or two of transition with brownish-purple flowers instead of either pink or blue. Start the treatment well ahead of blooming time. If you have purchased a white-flowering hydrangea, it will remain white no matter what you do.
Hydrangea care is pretty easy and straight-forward. For most varieties that bloom on old growth, you will want to prune after blooming for the best display the next summer. Prune the flowering shoots back to a strong bud or a strong branch. Once you take a closer look at the branches, it will be pretty obvious where to prune. For older, more established plants, you can remove up to one-third of the oldest growth to encourage new, vigorous growth. And please, even if you don’t want to prune for size, take some time to deadhead the browned flowers so the shrub will stay looking nice.
Some varieties bloom on new growth and these get pruned in the late dormant season (very early spring). You will need to check your variety as to what type of growth it will bloom on. Some even bloom on old and new growth and these are pruned to remove dead wood out in the early spring and then prune for shape after blooming.
And here is a tip: if you want fewer but larger flower heads, reduce the number of stems. If you prefer more blooms but smaller, leave those stems alone.
This is a good go-to shrub for most any coastal conditions, except very close to ocean spray. They are often found growing in ditches or in native areas where they have escaped from gardens, usually blue because of our naturally acidic soil. Even when left alone, they will not disappoint in their blue – or pink -summer finery.