In the summer, we often get several questions about hydrangeas. They range from "When do you prune a hydrangea?" to "Why isn't my hydrangea flowering?"...
FUN FACTS ABOUT HYDRANGEA
Hydrangeas are a diverse plant. They range from a few feet tall to climbing varieties. Some flower on new wood, old wood, or both. New wood would be considered the current season's growth, where as old wood is from the previous season (or older). You probably are wondering...Why is this important? Knowing what kind of hydrangea you have will help you care for it best!
WHAT KIND OF HYDRANGEA DO I HAVE?
There are 6 main types of hydrangeas that are commonly grown in the U.S., these include Big Leaf, Climbing, Mountain, Oakleaf, Panicle, and Smooth.
Panicle and smooth hydrangea flower on new wood. So, this means that the flower buds do not form until the plant leafs out for the season. These are very reliable bloomers in our zone because the flower buds are rarely killed by freezing weather.
Big leaf, mountain, oakleaf, and climbing hydrangea all flower on old wood. The buds on these plants form just after blooming (late summer) and must live through fall, winter, and spring in order to have showy blooms the following summer. These plants are a little harder to have reliably flower unless you know how to properly care for the plant. For our area, it is best to AVOID PRUNING. If you must prune, do it just after it blooms, however it is best to avoid pruning all together because you will be removing potential flowers with each portion cut off. Also in northern climates, it is best to put the plant in a protected location. Winter is not always to blame for killing the flower buds, it is acutally often the warm spring days we have followed by a cold snap. If you can't plant the shrubs in a protected location, put chicken wire around the shrub in early winter and cover with leaves. This will slow down the freezing and thawing of the buds and help keep the buds hydrated!
Re-blooming hydrangea are types of big leaf and mountain hydrangea that have the ability to flower on old and new wood. Even if the buds on re-blooming hydrangea are damaged in the winter, they can bloom on the new growth from that season.
Hydrangea do not need pruned to flower and grow beautifully. If you have a reblooming hydrangea or another type of big leaf, mountain, oakleaf, or climbing hydrangea, it is best to locate these varieties where they can grow to their mature height without needing to be maintained at a specific height. Panicle and smooth hydrangea can be pruned in the spring as soon as the new leaves are coming out. Remove up to 1/3 of the growth if pruning is necessary.