Why aren't some of my hydrangeas blooming? - Knowledgebase Question

Swansea, MA
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Question by etp109
July 17, 2005
I live in zone 6B and am a hydrangea collector with MANY species. I know that freezing of the buds and overfeeding will cause hydrangeas to stop blooming. I don't overfeed and I cover all of them with leaves for the winter.

I also read many books that say DO NOT prune hydrangeas except for the old DEAD stalks, because this will also cause failure to bloom. HOWEVER, many people in my area (the southcoast of Massachusetts) who come from Portugal, prune their hydrangea and they have incredible numbers of blooms - even after our harsh, cold winter. They tell me that it has to due with pruning exactly at the right time -- but it's just a sense, they can't really explain it! WHAT IS THE MYSTERY? I have many blooms on some mopheads but not on others. Also, my Nigra which grow on new wood and bloomed profusely the first two years, stopped blooming! WHAT am I doing wrong? Sincerely, Eileen Pereira

Answer from NGA
July 17, 2005
Since you're a collector of hydrangeas, you know that some bloom on new shoots which develop on old wood, and some bloom strictly on new wood. Those that are best adapted to your area are the kinds that, even if they freeze all the way down to the ground each winter, will send up new canes and each will bloom. Hydrangea macrophylla, the common garden hydrangea, blooms on new shoots which develop on old wood. As such, the oldest wood needs to be protected from freezing or you'll never get blossoms. With that said, all hydrangeas bloom on new wood (whether or not it develops from old wood) so some pruning is necessary, unless you have plenty of space for the plants to sprawl, and you don't mind bare centers in your plants.

I would disregard the caution against pruning, even with the macrophyllas. You can prune these guys down to 18 inches in the late fall and cover them with insulating material to keep the old wood alive. In the spring, flowering shoots will develop from the short canes that you left. The other types which freeze down to the ground each winter will develop new flowering shoots each spring so cutting away the old dead wood is a good practice.

It's true that too much nitrogen fertilizer can retard or even eliminate flowers so be careful with fertilizer. Hydrangeas generally are not heavy feeders anyway, so don't feed unless the foliage is off-color.

For best bloom, hydrangeas should receive at least a half-day of direct sunshine. If your summers are hot, provide morning sun and afternoon shade. If your plants are not blooming, and you haven't pruned them, you may need to relocate them to a sunnier area.

Best wishes with your hydrangeas!

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