I’m asked this question every year, and some years, I’m asked dozens of times. There are many different kinds of Hydrangea, but in most cases, folks are talking about Hydrangea macrophylla: Mophead Hydrangeas – the large shrubs with big blue flowers. The most common cultivar is ‘Nikko Blue’. Here’s how the Mophead bloom cycle works:
Year 1: The Mophead journey to blooming starts with the emergence of a new stalk from the base of the plant in the spring. This stalk will grow to the height of the mature shrub over the course of the summer, but will not bloom. If you examine a Mophead shrub in bloom, you’ll see that half – or more – of the stalks do not have flowers. These stalks are maturing and building a bud for next year’s bloom.
Year 2: The stalks that had no bloom during the previous summer will produce a flower. The stalks that produced blooms during the previous summer will be dead, with no leaves emerging from the stalk. There will be new stalks with leaves that are building a bud for flowering in Year 3
If anything damages the stalk during the year it takes to produce a bud, there will be no flower. For instance, if the plant is pruned too low in the fall or early spring, the buds will be removed, and the shrub won’t flower. If an early spring cold snap kills the buds after they’ve begun to emerge, there will be no flower. If the shrub is transplanted and sent into shock, there will be no flower. You’ll know that your Hydrangea is not going to flower if the only new growth is from the base of the plant, and none of last-year’s stalks produce .
There are always a few exceptions to this rule; Hydrangeas near the Sound are in a more temperate microclimate than those north of the Merritt, so after a hard spring frost, the southernmost plants may bloom, and their more northerly cousins may not. You may see one or two flowers after a tough spring, because some stalks can bloom the first year. Some. Not many. And only in a protected area. The ‘Endless Summer’ Hydrangeas, all the rage in the last few years, set flowers on first-year stalks, so theoretically, they should bloom every summer. I’ve not found this to be the case, and there’s been plenty of opportunity for observation, as three out of our last four springs have been brutal on Hydrangeas. Let’s hope for better this spring!
If you’d like to talk about ways to make your outdoor spaces more useful or beautiful, give DLTC a call. Ask for Patricia, Jon, or Dave, and let’s get started!