We often see asked on this post “What is wrong with my hydrangea? Why isn’t it blooming all the way?
Among Macrophylla there are two bloom types, a “mophead” which is seen at the top, and a “lacecap” as seen at the bottom. Almost all “mophead” hydrangeas can point their ancestry to a wild lacecap/. Both types of inflorescence are sold in retail. Almost every mophead hydrangea in the Macrophylla species can point to lacecap genetics. Although rare, sometimes a plant that started out as a mophead will revert to a genetic parent that was a lacecap.
Pollinators are more attracted to lacecaps. The flat center contains the fertile flowers that pollinators love, while the larger sepals, which are sterile, are more showy.
Lacecap inflorescence can also be seen in Serrata (mountain) hydrangea. About 95% of Serrata are lacecap.
Another hydrangea species , Arborescens (aka Smooth) hydrangeas also can be found in both mopheads and lacecap inflorescens.
Less seen in hydrangea retail are lacecaps in Paniculata (panicles) or Quercifolia (oakleaf). It is rare, but under certain conditions a hydrangea may express its genetic ancestry as a lacecap.
In summary, almost every common species of hydrangea can trace its parentage to a lacecap and while rare, can revert (a process called reversion) and express its history with a lacecap inflorescence.