Hydrangea macrophylla is native to the mountains of Japan, which have a similar climate to the east coast of the United States. They grow best in afternoon shade in a well-drained soil with regular moisture. Some varieties change color with the soil pH, having blue flowers in acidic soils and pink in more alkaline soils.
The most common issue with bigleaf hydrangeas is failure to bloom. This could occur for many reasons, but often occurs due to very cold winters or a late frost that kills the flower buds. Because they bloom on “old wood” from the prior year’s growth, the developing flowers are present in dormant buds throughout the fall, winter, and early spring. If the buds are lost to cold weather or damage, such as pruning or wildlife grazing, the shrubs will not bloom or will bloom very poorly that year. To avoid this, make sure to prune your hydrangeas right after they finish blooming, and no later, and only prune if necessary. Use wildlife repellant or fencing if deer are a problem, and try to plant hydrangeas in areas that are sheltered from cold weather (such as against a foundation or other structure).
Cold weather damage is not entirely preventable, so there may be some years when you do not get many blooms. However, if your hydrangeas are leafed out and a late hard freeze is predicted, you may try to protect your shrubs by placing sheets over them in the late afternoon before the temperature drops, to try to retain some heat. If you have a larger planting that is impractical to cover with sheets, you can try spraying them down with a water hose in the evening or at night. Because freezing is an exothermic reaction, when the water freezes it releases a tiny amount of heat that can help prevent the water inside the plant from freezing, which is what causes frost damage. This will work if the temperature doesn’t drop too low. This tip also works for other spring-blooming plants and fruit crops.
Hydrangeas often have dead branches that need to be pruned and removed in the spring, but make sure to wait until the buds have broken and leafed out so you can clearly see which parts of the branches are dead. This is typically the only pruning needed for hydrangeas, unless some branches need to be trimmed back from a bench, steps, pathway, etc.
- Opposite leaves, ovate with a large-toothed margin.
- Flowers are borne in large clusters called panicles, which may be large and round or flattened.
- Individual florets typically have 4 large colorful sepals, which prolong the life of the blooms, but these florets are also sterile and do not produce seeds. The true flowers are very small and more commonly seen in the centers of lacecap hydrangea blooms.
- Typically, blue, purple or pink hydrangeas are Hydrangea macrophylla. Other species’ flowers are white, green, or brownish pink, but not bright pink or blue.