I have a bigleaf hydrangea, about 4 feet tall. It is well-established, but has only one big blue flower. It has fewer flowers every year. What is the problem?
The Gardener’s Answer
Hi, Phil: There are a few reasons that may explain the lack of blooms on your bigleaf hydrangea (Hydrangea macrophylla). In some cases, the specific cultivars are marginal and the flowers are not hardy. These are typically purchased at florists and not at a garden center or nursery. This does not seem to be the case with your shrub since it has bloomed for consecutive years. Other possibilities are lack of sunlight, nutrients, or both, and pruning at the wrong time of year. Is it possible that your hydrangea is receiving more shade than in the past? If your shrub is growing in dense shade, it would benefit from more sunlight, preferably morning light and afternoon shade. How often are you fertilizing? Hydrangeas will benefit from a side dressing of compost or a slow-release, well-balanced fertilizer such as 10-10-10. Avoid feeding them in late summer since they are getting ready to go dormant and this will encourage growth that can be damaged by early frost. They can be fed twice during the growing season. Always follow recommended application rates since overfeeding our plants can have the reverse effect in that too much nitrogen will stop them from blooming. Hydrangea macrophylla bloom on growth from the previous year (old wood) and they should be pruned after they have finished blooming in the summer. Pruning at other times of year will result in bloomless hydrangeas. They should not be pruned in the spring other than to remove dead wood.