For this question about Hydrangea macrophylla (commonly called bigleaf or French hydrangea), we've asked Mariana DiVita to help us understand the flowering whims of this hydrangea species. Mariana is a Master Gardener from Cherokee County, Georgia. We attended her Hydrangea Seminar earlier this month and liked her style and information so much, we asked her to share it here. Thankfully she agreed! We give the space now to Mariana . . .
Have you ever driven by an old farm house and seen a hydrangea blooming beautifully with gorgeous blue or pink mopheads and wondered why the one in your yard is green and flowerless? This seems to be a common question about one of our favorite shrubs. There can be several reasons your hydrangea may not bloom.
1) Late Spring Freezes
The first reason is out of your control unless you have an “in” with Mother Nature. Here in Georgia, a late spring freeze can ruin our hydrangea season in a hurry.
Spring temperatures in the South can get a little crazy. One day it's 35 degrees and the next it's 70 degrees. If we get too many warm days in a row, the hydrangeas start to leaf out or “break bud” and then Old Man Winter hits us with one more hard freeze. This can damage the bud tips and result in few, if any, viable flowers this year.
The good news is the new remontant (fancy word for re-blooming) varieties will bloom on old and new wood so you may have a flush of flowers later in the season.
2) Timing of Pruning
The next question is “Did you prune your hydrangeas and if so when?”
I admit our beloved hydrangea is not the most attractive plant without its leaves. Did your well meaning spouse or landscaper decide to cut the “dead sticks” back this winter?
If you pruned your hydrangea after August 1 last year, you may have cut off this year's flower buds. After August 1 you risk pruning the flower buds that have formed for next year.
Hydrangeas don't need annual pruning. The only reason to prune is to remove the dead stems and tips and remove crowded stems. Sometimes a stray long branch or two need to be pruned to reshape the plant. I know there are people who prune to reduce size. I believe its important to make sure there is sufficient room for the full size hydrangea when it is originally planted but sometimes you inherit what someone else planted. If your hydrangea is oversized for its space, consider moving it this fall. You will need to cut it back before August 1 and then move it once the weather cools.
3) Too Much Fertilizer
Another reason that you may have a very lush green plant and no flowers is over fertilizing.
In this case, more is not always better. That does seem counter intuitive, but if you over fertilize you can have lush foliage and no flowers.
Hydrangeas like a slow release, balanced fertilizer (example: 10-10-10) two or three times a year in March, May, and July. You do not want to fertilize after August 1st. The amount of fertilizer varies with the plant size so read label directions. It is better to under fertilize than over fertilize.
4) Not Enough Sunlight
Lastly, the lack of blooms may be due to the amount of sun your plants are getting.
In my perfect garden world I would have all morning sun with an eastern exposure and protection from the hot afternoon sun! Many plants here in the South would find this to be a perfect planting site. Hydrangeas are no different. If your hydrangeas are in heavy shade, there may be few or no flowers.
In my own yard, the canopy of the mature trees over one of my hydrangea beds has blocked a lot of sunlight and my hydrangeas don't have many flowers. My hydrangeas on the east side of the house that get the morning sun until noon are blooming beautifully. So what will I do with my shady bed of flowerless hydrangeas? I will be moving these hydrangeas to a spot with more morning sunlight and converting this bed to ferns, Japanese maples, and hostas. A gardener's work is never done!
I hope this help solves your hydrangea flower mystery and may your hydrangea blooms be abundant next year!