|H. macrophylla is a deciduous, rounded shrub that has ovate, toothed green leaves to 8 inches long. Enormous flower clusters to 8 inches across bloom in summer and early fall. Lacecaps have small fertile flowers in the center of the cluster, surrounded by larger, four-petaled sterile flowers. Hortensias, also known as Mophead Hydrangeas, have clusters made up of only large sterile flowers. Pink or blue flower color is determined by soil pH. White varieties are not affected by soil pH. Hydrangeas do best in moist, well drained, moderatly fertile soil that is rich in humus. Protection from winter winds and extreme cold is best. Cultivars of Hydrangea macrophylla fall into either Lacecaps or Hortensias. Red to pink flowers occur in alkaline soils and blue to purple flowers in acid soils. Hydrangeas can be forced to change flower color, however, this must be done before bloom begins. To make or maintain blue flowers in alkaline soils, treat with aluminum sulfate. To make or keep pink flowers in acid soil, add lime.