Hydrangea

The basics species of this large bushy North American shrub has flowers that are a mixture of tiny fertile florets and the larger more showy sterile ones, which in fact have coloured bracts in place of petals. The variety 'Annabelle' has only sterile florets, which makes the flower heads much larger, like spectacular white balls up to 30cm (12in) across. Plants are nominally very hardy but late frosts can damage the buds, so grow them in a sheltered corner or against a warm wall in cold gardens. Regular pruning keeps the naturally open plants dense and compact. The Royal Horticultural Society has given it its Award of Garden Merit (AGM).