I have a mophead hydrangea that is about 3 years old. I don't know the specific variety.
In May, I gently pruned it for shape. When summer came, there were only 3 - 4 blooms on the shorter branches. Maybe on ones I hadn't cut? It bloomed well last summer. It gets plenty of sun and has good soil.
Next to the blue hydrangea are two, pink mophead hydrangeas which I pruned at the same time, also 3 years old, which flowered fine this summer.
Can anyone suggest when / how I should prune the blue mophead in the future?
How to Prune Blue Mophead - variety unknown
After bloom is the best time to prune. When you prune in spring you're removing growth with the buds that become blooms.
Two things could have happened here. The blue might not be as hardy as the pink and the buds were winter killed or you cut the buds off when you pruned. Most, but not all, Hydrangea macrophyllas bloom on old wood. In other words flower buds for next year are foming this year. Cut that wood off and you lose the flower buds. Without knowing the exact name of the pink variety I can't explain why you didn't also cut off those flower buds. It's possible they are hardier and bloomed from buds lower on the wood. Or, it's possible it's a remontant variety that blooms on new wood, wood that is produced in the same season as the flowers. There aren't many remontant varieties.
You really need to know the hydrangea cultivar names. It shouldn't be hard to track down the name. Search for a variety that won't turn blue in acid soil, which you seem to have, if some of your hydrangeas bloom blue without help. I can think of one - Hydrangea serrata 'Preziosa'. While not remontant (or a H. macrophylla) it's a very hardy mophead type and will bloom from buds lower down if the top ones are winter killed or lopped off. 'Preziosa' will not turn blue - no matter what the soil.
Thank you for the replies.
After a closer inspection of the blooms on both pink and blue hydrangeas:
The 4-5 blooms on the blue mophead all originated from a woody stem. The newer-looking, green stems grew quite tall but have no blooms.
The pink blooms on the other bushes are both on woody and green stems, although most blooms came from the woody stems.
Sadly, I don't know which varieties I bought. Is there any way to find out?
We have fairly neutral soil. The pinks have become more purple (I add nothing to their soil). To get a nice blue, I add acid to that hydrangea. Otherwise, the blooms are so pale the appear white.
If I prune now, am I cutting off buds forming for next summer's flowers?
We also have macrophyllia Angel Robe and Angel Eyes. Should I prune them after blooming, too?
The only safe time to prune any H. macrophylla is right after they have bloomed. If you prune now you'll cut off next years flowers. Why do they have to be pruned? For appearances sake the most they need is to have the old faded flowerd heads removed. Other wise they're usually left alone.
I thought they should be pruned because some branches are quite a bit bigger than others, and the bush looks a bit odd. However, I'd rather have blooms!
Thank you for the advice.
I'm very jealous of your zone.You should be able to grow any Hydrangea you want with no worries about winter killing the buds. Enjoy!