The wild Hydrangea macrophylla (syns. H. hortensis, H. opulordes) is a species of flowering plant, in the family Hydrangeaceae, which comes from Japan. In their original state, the blossom clusters are formed of two distinct components. The deciduous shrub growing to 7 ft tall by 8 ft broad blue flowers comes in the autumn and summer. In the center of each flattened cluster are tiny fertile florets, and around the outside are others that are sterile and much longer. The overall effect is somewhat lacy, and cultivars have acquired the group name of Lacecap.
An increase in sterile florets at the expense of fertile ones has resulted in the popular hydrangea group known as Mopheads or, more technically, Hortensias. They are less elegant than the Lacecaps, but make a more striking display in the garden. Nevertheless, several Lacecap cultivars have found favor among gardeners and some have received awards.
Particularly fine is ‘Blue Wave’, which is blue on acid soil and pink on alkaline soil. For many gardeners, a good display of mop-headed Hortensia hydrangeas at once evokes the memory of a West Country holiday. The plants certainly thrive in the moist atmosphere and relative freedom from the hard frost of that area, making rounded, 5 ft high bushes covered in flower heads.
Except in the West Country and other very mild parts, it is vital to choose varieties selected for the open garden. Those bought for house decoration and then put outside may not flower or may barely survive. Most of them need the shelter of a wall.
One fine variety that does not be ‘Générale Vicomtesse de Vibraye’. From July onwards this bears large heads of flowers that are clear pink on alkaline soil, blue on acid soil. At summer’s end, they turn papery and become tinged with lime-green.
If you want to grow Hydrangea macrophylla, then plant in spring in humus-rich, moist soil. On acid soil, blue flower color persists, on alkaline soils, it turns pink. But on the latter, alkalinity can be reduced with aluminium sulphate or proprietary blueing powder. Shelter and dappled shade provide ideal conditions.
Blue Wave is an attractive and vigorously growing Lacecap hydranges which has achieved great popularity. It has many names, like French hydrangea, bigleaf hydrangea, mophead hydrangea, hortensia, lacecap hydrangea, and penny mac.