Something strange is happening to my Annabelle hydrangeas. I have five planted in my front yard, one on the north side of my steps and four on the south. They were planted six years ago, and I added one more on the south end this year. They have been beautiful and (seemingly) healthy until last year. The one north of the steps started growing a few flowers that were flat, with a ring of small petals around the perimeter. The pollinators love these, much more so than the normal Annabelle blossoms. There were also a number of the regular, big, ball-shaped flowers. This year, that same plant is almost entirely that small, flat flower. Only four or five regular flowers on the plant.
And, a big concern, I noticed two or three of the bushes south of the fence have these same small, flat flowers again. Interestingly, my brother who lives on the north side of the city has one hydrangea out of about five showing these same flowers this year, and my sister-in-law in Des Plaines said she noticed some hydrangeas in her neighborhood that also have these same type of flowers. I have attached a few photos.
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Any idea what’s happening? Should I remove all the bushes? (I would hate to have to do that.) Any help is much appreciated. Thank you.
— Mary Staackmann, Morton Grove
You most likely are seeing hydrangea seedlings coming up that will look different than the cultivar Annabelle, which you originally had installed. Annabelle hydrangea is a cultivar of Hydrangea arborescens (smooth hydrangea), which will tend to have flowers that are more flat than the round flowers found on Annabelle hydrangea. I also have a seedling hydrangea sprouting in with a row of Annabelle hydrangeas in my garden, and over time it has gotten taller with larger leaves than the adjacent Annabelle hydrangeas. This plant became more apparent as it has gotten better established, and one could easily think that something has happened to the original Annabelle hydrangea. It is starting to overtake the adjacent Annabelle hydrangea.
Carefully remove the seedling hydrangeas that have become established in your planting if you want to maintain a uniform planting of Annabelle hydrangea. Wait until the plants are flowering if you cannot identify the ones to remove. For now, I am letting the seedling be in my garden but monitoring to make sure it does not take over — attracting more pollinators to your garden is a good thing.
Annabelle hydrangeas are easily grown and perform best in sites with partial shade and evenly moist but well-drained soil. Full sun will be OK, too, if the plants are given adequate water. They flower on the current season’s growth, so cut stems back to the ground in late winter. New shoots will emerge from the base and flower heavily the same summer.
A group of Annabelle hydrangeas planted in dry shade under an oak tree in my garden do not perform well, because of the dry conditions, so it is important to make sure this hydrangea gets enough moisture for optimum performance. I only water established plants at home during very dry periods when I see them wilting. The Annabelle hydrangeas are much smaller in this location than ones in other locations in my garden and do not flower as heavily. I did not cut them back this spring, and this seemed to help their vigor. It is a good idea to understand what a plant needs from a cultural perspective for the best performance and then experiment with different maintenance techniques when you are pushing its limits some.
Tim Johnson is director of horticulture for the Chicago Botanic Garden in Glencoe.
If you have plant or gardening questions, contact the Chicago Botanic Garden’s Plant Information Service at 847-835-0972.
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