Hydrangea Flower Form Change: Mophead to Lacecap Explained

A gift hydrangea bloomed as a mophead (all sterile flowers) last year. This year it's a lacecap (fertile center, sterile ring). The gardener asks how this happened.

Explanation

This is a natural variation in Hydrangea macrophylla. Many cultivars are genetically unstable chimeras or have variable expression of sterile vs. fertile flowers due to:

• Environmental factors: Temperature, light, and nutrition during bud formation affect flower morphology.
• Age of wood: Flowers on old vs. new wood may differ.
• Pruning timing: Alters bud development conditions.
• Cultivar tendency: Some (e.g., 'Mariesii', 'Lanarth White') naturally produce lacecap or mixed forms.

Is It a Problem?

No. The plant is healthy. Lacecaps are equally beautiful and attract more pollinators. The change doesn't indicate disease or nutrient deficiency.

What to Do

• Enjoy the variation year to year.
• Maintain consistent care: morning sun, even moisture, acid soil, prune only after flowering.
• If you prefer mopheads, select cultivars known for stable mophead form (e.g., 'Nikko Blue', 'All Summer Beauty').

This is a fascinating quirk of hydrangea genetics, not a flaw.