For the record
It’s hard to argue with the magic of large-leaf hydrangeas in the garden as they progress from mid-summer into fall.
Botanically known as Hydrangea Macrophylla, this species consists of two species: Hortensia (mophead) and lacecap.
Moufheads, with their large, globe-like blooms made up exclusively of male flowers, have long been a staple shrub in many gardens. But lace caps, resplendent in their decoration of flat-headed discs of short female flowers surrounded by larger male flowers, are gaining popularity.
The Macrophylla variety is the largest type of hydrangea and is easy to care for, but its placement in the garden is crucial. Both mopheads and lacecaps prefer morning sun and afternoon shade. Too much hot sun and there is a risk of burning leaves and flower petals.
They prefer soil rich in humus, although they will do well in less demanding conditions. Regular water is essential, but hydrangeas resent being overwatered, so good drainage is essential.
Soil acidity is not very critical with hydrangea. They tolerate acidic and alkaline conditions. In fact, when large plants are in flower, it is a good indicator of the pH value in your garden. Blue flowers indicate acidic soil; Pink means alkaline.
But what if you want to change the color of the flower? In fact, it’s better to get a handle on the pH of the soil in your garden than to mess around with adding chemicals. This upsets the balance in your soil and can affect soil microbes and other plants nearby.
But if you need pink flowers instead of blue, it is better to move the hydrangea to a larger pot where the soil change will not affect neighboring plants. However, the “fix” is the same even if you have to leave your shrub in the ground.
To change the blue color to pink, annual adjustments to the limestone or chalk (calcium carbonate) are required.
Changing pink to blue is more difficult. Best success is achieved by moving your hydrangea to a large pot and applying annual amendments of aluminum sulfate. (Check your garden center for “compound hydrangea bloom.”)
However, there are supposedly new hydrangeas on the market that maintain their color regardless of soil pH. Warning: My decidedly pink color is now blue.
Trimming both mopheads and lacecaps is easy. They bloom on last year’s growth, or old wood. I usually wait until my large-leaf hydrangeas start forming leaf buds in the spring before I start cutting them back.
The first thing to do is to cut the ends of the branches into two opposing healthy leaf buds. If there is only one bud, cut it back to the healthiest bud.
Next, I evaluate the health of each branch, looking for the oldest ones, and any that may have winter damage. Making sure to remove only a third of the total number of branches on the shrub, I cut off the broken ones, and then as many branches as I could to complete the count. However, if only a few old, annoying branches remain, remove them.
Some other hydrangea types worth mentioning:
Hydrangea anomaly subsp. petiolaris – (Climbing) – Slow growing and doesn’t mind a north-facing location. Prune immediately after flowering.
· Hydrangea Bushes – (Smooth) – They bloom on new wood so can be pruned back hard. Soil acidity does not affect flower color. ‘Annabelle’ is a good variety.
· Hydrangea paniculata – These are the hardiest…most are classified in zone 3. The flowers are cone-shaped and the plants can tolerate full sun. ‘Limelight’ and ‘Pinky Winky’ are two varieties.
· Hydrangea quercifolia – (oak leaf) – It is known for its leaves that resemble those of an oak tree and its stunning autumn color.
Leslie Cox co-owns Growing Concern Cottage Garden in Black Creek.