Here’s why hydrangeas turn green

Q. I noticed my hydrangea flowers are turning green. Why did they do this? Is there something wrong with my hydrangea plant?

Anonymous From the Canfield Fair

A. First, there are several different types of hydrangeas and you did not specify which one you have, so I will assume taking about a macrophylla (Bigleaf) hydrangea since a lot of people have this type here in the Mahoning Valley.

These hydrangeas have large showy flowers whose colors are either pink or some shade of blue. As the bloom ages and the days become shorter in late August the pink or blue colors give way to green. This is a natural change and your hydrangea should be fine again next year. Why do the flowers turn green? The flowers start out green in the spring. As the days get longer the added light gives the pink or blue colors in the blooms the energy they need to overcome the green color. These colors can last for several weeks, then as the days grow shorter the colors begin to fade back to green.

The blooms on other types of hydrangea can also turn green this time of year. At least, for the most part. While all of them turn some hue of light green, certain cultivars have other hues when dried. Hydrangea paniculata “Vanilla Strawberry” turns a medium pink/purple in October if grown in more shade or if provided adequate amounts of water throughout the bloom period. See a picture of the faded blooms of this plant at http://go.osu.edu/hydrangeafacts.

To make sure your macrophylla hydrangeas will be their best next year, you should have the soil around the hydrangeas tested. A soil test will show if there are any nutrient deficiencies that need to be corrected and what the pH (acidity) level is. By the way, it’s the pH level that determines what color the hydrangea blooms will be on these types of hydrangeas. A lower pH means blue while higher soil pH gives you pink blooms. For more on the color changes of hydrangeas, check out the link above.

If you want to dry the flowers and keep the blue or pink color, you’ll need to harvest the flowers while they still have color, but as they have just started to fade on the edges. August through October are the prime times to get colors with the drying process.

Thanks for stopping by the Mahoning County OSU Extension exhibit ate the fair.

This week’s answer was provided by David Sprague, an OSU Extension master gardener volunteer in Mahoning County. You can meet him at the Mahoning Plant and Pest Clinic. Call the clinic at 330-533-5538 to submit your questions. Regular clinic hours are 9 a.m. to noon Mondays and Thursdays.