Hydrangeas are a beloved summer flower, but there may be a few things you don't know about your favorite warm-weather bloom.

When the summer season fades into fall, we obsess over one last-standing flowering shrub: the hydrangea. It evokes an old-fashioned charm with its pretty pom-pom shape and ethereal shades of pink, blue, and periwinkle. Learn the untold mysteries behind these blooms, which are among Martha's favorites; doing so will help you better care for every hydrangea in your garden.

There's a hydrangea care tip built into the shrub's name.

What's in a name, you wonder? When it comes to "hydrangea," the answer is a secret gardening tip. The name hydrangea originates from two Greek words: "hydro," a prefix meaning "water," and "angeion," meaning "vessel" or "container." Together, the rough translation is "water vessel," which refers to hydrangeas' exceptional thirst for water. For a planted shrub, the soil should be moist—not wet, or this can stunt the hydrangea's growth—about eight to 10 inches deep. Do a manual test with your finger. A bouquet of cut blooms, on the other hand, can be easily rehydrated if you float them in a sink or tub filled with cold water for three to four hours. It also helps to refresh your hydrangeas this way every few days to make them last longer in a vase.

hydrangea bouquet arrangement in pink vase
Credit: Getty Images

You can thank one woman for your love of these shrubs.

Harriet Kirkpatrick is the woman who allegedly discovered Hydrangea arborescens (the "Annabelle") and shared their beauty with her community. According to local legend, Harriet was horseback riding out in the woods of Union County, Illinois, when she came across a hydrangea bush in full bloom. She was immediately enamored with these flowers reminiscent of fluffy, white snowballs. Excitedly, she told her sister Amy about the discovery and they returned to the secluded spot to transplant them into their garden. The Kirkpatrick family, of the famous Anna Pottery, shared them with family and friends. Word spread, popularity grew, and soon hydrangeas were blooming all over town. Now, more than a century later, the name Annabelle honors the two "belles" from the town of Anna who discovered it. And to the joy of local hydrangea lovers and horticulturalists, the town mayor officially declared the second Saturday of June as Annabelle Hydrangea Day.

You can change a hydrangea's color.

The secret is in the soil, or more specifically, the soil's pH level. Adjusting the measure of acidity or alkalinity in the soil can influence the color of your hydrangea blossoms. Acidic soils (pH 0 to 7) tend to deepen blue shades, while alkaline environments (pH 7 to 14) tend to brighten pinks. If you want to try it for yourself, you can check the pH of your soil with a simple test kit available from your local nursery. You can adjust the soil's pH at the time of planting (increase the acidity by adding peat moss and sulfur, or increase the alkalinity by adding lime). The colors won't change overnight, but when they do, it's like magic.

Proper pruning is key to hydrangea care.

It is true for many species (of the 70-plus varieties that exist) that hydrangeas produce their big, clustered blooms from the tips of shoots that were pruned in the previous season. But not all species make the cut, so to speak. To know whether or not your hydrangeas need pruning, first determine the species and whether it blooms on new or old wood. If your hydrangea blooms on old wood (stems cut during the previous season), the shrub should be pruned immediately after the flowers fade, or expect a bloomless next season. If your hydrangea blooms on new wood (stems cut during the current season), the shrub should be pruned later, prior to the new growth.

Species H. arborescens and H. paniculata both bloom on new wood. Conversely, species like H. macrophylla and H. serrate bloom on old wood. And then there are "reblooming" hydrangeas like H. macrophylla cultivars flower on both old and new growth, so no timed pruning is required. If you're unsure, ask your local gardening supply store for the proper pruning of your hydrangea.

Boiling water is a secret for reviving cut hydrangeas. 

To care for your cut hydrangeas and prevent blooms from wilting prematurely, try this tip: Cut them early in the morning or late in the afternoon, and place the ends of each stem in boiling water for 30 seconds, making sure that the steam does not burn the flower head. Then, plunge the cuttings up to the flower head in cold water. Drape paper towels across the tops of the blossoms to cover them completely. Tuck paper towels down into the container (don't squash the flowers), and mist. Do not allow the paper towels to dry out. In four hours, your hydrangeas will be fully conditioned and ready for arranging.


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