The amazing technicolor hydrangea

    As the first chorus of roses exits the stage, the intermission is brief before the return of the garden’s next great act, the hydrangea.

    There are many varieties of great value, such as the native Hydrangea arborescens and Hydrangea quercifolia, but my favorite has always been Hydrangea macrophylla from Japan. Its softball-sized blue globes decorate the shrub from top to bottom starting in June and continuing for most of the summer.

    In recent years several new cultivars have been heavily promoted as superior because they bloom on the current year’s wood. Avoid these plants. Our Philadelphia winters are mild enough that hydrangeas don’t suffer dieback and deprive you of flowers the following summer. The new “endless” blooming plants have smaller flower heads and the color is a pale, anemic blue or lavender at best. Much preferred (by me) are the older mophead varieties that bloom a shocking deep ocean blue, sometimes violet, colors rarely seen in other flowers. Sometimes these can be difficult to find commercially, but hydrangeas are among the easiest plants to propagate.

    If you’d like to reproduce a particularly nice hydrangea, bend a flexible branch of the plant to the ground. Scrape the outer bark off one side with your fingernail and weigh the branch down with a brick or rock, making sure the scraped part of the branch is making contact with the ground. In a few months roots will form here, and the new plant can be severed from the mother. Hydrangeas grow fast, so within a few years you will have a mature specimen.

    Unlike almost any other plant, the color of hydrangea blossoms is greatly influenced by elements in the soil. Aluminum is the agent responsible for the blueness, and in acidic soils more aluminum is readily available. The Philadelphia region generally has acidic soil, so most of our hydrangeas will be blue, or maybe purple if a plant is near a foundation or some place where lime has seeped into the soil. If you travel to another region you may be surprised to see only pink hydrangeas. By changing the pH of the soil a gardener can have some influence over color, and perhaps achieve a more saturated flower.

    Even if it were possible to make them change, I like blue hydrangeas. I like pink flowers too, but in nature pink is the default setting of many plants, from roses to phlox. Blue is owned by sky and water, and fairly few flowers share the color (those that do tend to be tiny, like forget-me-nots.) Gazing out at a row of deep blue hydrangeas is like having a view of open sky and the ocean, a mini-vacation without leaving home.

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