Hydrangeas bloom, but stay green

(Question)

My hydrangeas (hydrangea arborescen) seem very healthy and always bloom. The blossoms are green at first, sometimes turn white, but then turn back to green and stay that way. They are in two beds at the front of my south-facing property (in the Beach neighbourhood in East Toronto) in the shade of three large, old oak trees. The easternmost bed gets less sun than the western bed, but that doesn’t seem to affect the colour. Also, I prune them back every fall. They were planted about 10 years ago and used to turn white and stay that way. Any idea what’s making them turn green? Is is the soil?
Thanks very much for your help,
Karen Watson

 

(Answer)

You are lucky that your hydrangea aborescens are so healthy; and always bloom.  You should not be concerned about the changing colour of the blossoms as changing colours is the normal aging cyle for the blossoms of most hydrangeas. In the case of hydrangeas aborescens the normal progression is for the blossoms start off green; then turn white and gradually turn back to green.  So it is unusual that in the past the blossoms on your shrubs turned white and stayed that way. However, given that that was their patterns, last year’s long cool wet summer may have prompted your shrubs to turn revert from white to green, or fail to turn white, more quickly than has been the case in years with more seasonal summer warmth and light.  This year you may be surprised with more white blooms that in recent years. You may be able to prolong the period where the blossoms are white by that your shrubs are kept healthy, i.e. ensuring that they have adequate moisture.