Why aren’t my hydrangea’s flower heads full?

When I moved into my house a number of years ago there were three large well established hydrangea bushes gracing the back garden. The first summer none of them flowered very well which I put down to the general neglect they had suffered over past seasons, and in particular the massacre they had received by the “landscapers” who were brought in to “tidy up” the garden before we moved in. They had cut back most of the hydrangea bushes onto their old woody stems thus removing the spring flower buds which form on the new green softer growth.

The next year I was careful to leave the few dead heads that had flowered over winter to protect the new growth from frost. I removed the dead flower heads once the risk of any frost had passed and pruned the new growth down to the first set of strong buds beneath the faded flower head. I applied a specialist fertiliser enriched with horse manure and the flowers that summer were much larger and more prolific. Out of my three hydrangea bushes two produced lovely full flower heads but one of the bushes much to my consternation produced flower heads with blossoms only forming a perimeter around small flower buds which to my untrained eye seemed to not be developing how they should have. That’s when I opened my gardening encyclopedia and discovered that the common “French hydrangea” – Hydrangea macrophylla actually has two common cultivars (there is a third Hydrangea macrophylla ssp. serrata – but this isn’t as common)  – mophead which is what I expected all of my Hydrangea macrophylla to be and lacecap – Hydrangea macrophylla normalis which is what my third hydrangea bush was.

Hydrangea macrophylla – Mophead Hydrangea

Also known as the French or florists hydrangea this hydrangea features the large mop like heads of flowers which are the most widely recognised hydrangea. The colours of the flowers on hydrangea macrophylla have historically varied from pink to blue depending on the acidity of the soil – acid soils giving blue flowers and alkali soils producing pink blooms with neutral soils usually giving a mix of blue and pink flowers. Nowadays cultivars of hyrdangea macrophylla feature dark blue and even white varieties.

white hydrangea macrophylla

Hydrangea macrophylla normalis – Lacecap Hydrangea

This hydrangea features sterile “regular” hydrangea blooms circling a centre of fertile flower buds.

Althought the mophead hydrangea produces the most impressive flowers to the amateur eye, a gardening connoisseur will take great pleasure from the lacecap hydrangea with it’s interesting circle of blooms.

So if you are wondering why your hydrangeas flower heads are not full – take a step back and appreciate the elegant and somewhat different beauty of your lacecap hydrangea!


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