Amy N. told me about her hydrangea with lots of beautiful deep green leaves, and nothing else. Not a single flower. Nada. “Why won’t my hydrangea bloom?” she asked. I had a mental picture similar to the one below:
After questioning her and establishing that it gets the proper amount of shade vs. sun, is in good soil, and was covered during our last cold spell, etc., I asked when she last pruned it. She had pruned it in the spring.
I suspect that is the problem, or at least part of the problem. Because the huge blossoms grow only on new growth, springtime pruning removes the flower buds that may not even be visible yet. Simultaneously, late winter pruning of old wood may cause the same problem because it is the old wood that carries the new stem and leaf buds from which the flower buds will emerge.
After asking if it is likely to outgrow it’s available space, and learning it has plenty of room to grow quite large, I suggested she not prune it at all. Of course, after it blooms, she will want to remove any spent flowers in the late summer or fall. Removing spent blooms encourages more flowering.
I like to cut hydrangea flowers for indoor arrangements. Cut them when the flowers are at their peak, and they will last for weeks. They won’t wilt as most cut flowers do. Instead, they will gradually dry out, and make great dried flowers, too. The photo below is of some white Annabelles I grew in my yard in Alabama.
Another possibility for the lack of flowers could be too much nitrogen. Amy top-dressed her hydrangea with Black Kow. Composted cow manure has lots of nutrients, but is typically low in nitrogen, so that’s not likely to be the problem. It could be that any other fertilizer or plant food she may have used, or that may have been used on the lawn near the hydrange is too high in nitrogen.
Remember “NPK” the letters that are represented by the numbers on fertilizer bags? NPK stands for nitrogen (N), phosphorous (P), and potassium(K); and the numbers will always appear in that order. The numbers indicate the percentage of each nutrient that is present in the bag. Nitrogen produces very green grass, as well as more leaves and top growth on plants. Phosphorous produces more flowers and fruit, and strengthens root development. Potassium produces strong healthy plants.
A fertilizer numbered 26-3-3, or any combination with a larger amount of nitrogen is a good fertilizer for turf grass, but NOT for flowering plants. For flowers and flowering shrubs a fertilizer with a higher middle number (phosphorus) is needed. Some examples of this are 15-30-15 and 5-30-5.
I know that with tomatoes, too much nitrogen will produce lots of pretty leaves, but a less than normal amount of fruit. I suspect that is what’s going on with Amy’s hydrangeas.