Huge blue bloomer goes multicolor

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Hydrangea's look influenced by pH levels

By Sarah Berkshire

Decades ago, Carrie Richardson accepted a small piece of a relative’s hydrangea. She and her husband toted the starter, wrapped in brown paper and placed in a small foam cooler in the trunk of the car, from Alabama to their home in Elizabethtown.


That might have been during the ’70s. Richardson doesn’t quite recall. But that piece of plant — which she was told wouldn’t do so well once taken from its sandy Alabama soil and warmer climate — has grown and grown. It’s roughly the size of a compact car, though Richardson hasn’t done much to it since her late husband planted it.

Vibrant blue flowers had made their appearance every year. But this year, the blooms came in blue, pink and purple. The colors and the sheer size of the plant, Richardson said, has been a treat for her and, apparently, for those whose eyes are caught as they pass her house.

“A lot of people ask me, ‘Where did you get it? I’d like to get a piece of it.’ And I say, ‘No, we’re going to leave it alone,’” she said.

It turns out the color of hydrangeas — bigleaf hydrangeas are an especially common variety in this area — can be manipulated, with or without intention.

White is always white, but pink and blue blooms depend on the soil’s pH levels, said Amy Aldenderfer, Hardin County Cooperative Extension agent for horticulture.

Levels of six to seven will produce pink flowers; five to six likely will produce purple and pink; and levels dipping below five will produce blue blooms. And as levels vary from one patch of ground to the next, so can the blooms on a large plant.

Gardeners can add lime to raise the pH. Aluminum sulfate or elemental sulfur will decrease the pH.

The cooperative extension, by the way, tests soil for free.

Soil in this area naturally has a pH level of six and a half to seven, said Hugo Davis, owner of Bluegrass Garden Center and Landscaping in Elizabethtown. So a hydrangea growing in Hardin County likely will turn pink at some point.

This year’s early warming and spring cold snap might have worked to intensify the color, too, he said.

Still, Richardson’s plant had bloomed blue for decades, never giving in to Kentucky’s lime-rich soil.

It’s possible, Davis offered, that a longtime blue will change because its roots have reached some source of lime. The lime in a gravel path or concrete sidewalk, for example, could turn the flowers pink.

Sarah Berkshire can be reached at (270) 505-1745 or sberkshire@thenewsenterprise.com.