Propagation
Take soft tip cuttings during late spring and hardwood cuttings in late winter.
Note:
Transplant when dorment and plant out during early summer or autumn.
Botanic information
Leaf: The leaves are broad ovate to oval with a coarsely serrated margin and are arranged oppositely to decussate. The underside is dull green and slightly pubescent. The apex is acuminate and the petiole is up to 35mm (1¥in) long.
Flower: The tiny central flowers are stellate and arranged in a dense terminal corymb. There are two types: Hortensia that has large rounded flower heads with 4 petals like sepals. Lacecap; large flat flower heads, pink flowers in alkaline soil, blue flowers in acid soil. The flowers are mostly sterile and appear from late spring to early summer.
Fruit: The flowers are mostly sterileand the fruit is not commonly seen. The plant is normally reproduced vegetatively to maintain true to type.
Culture
Prune
To produce the largest number of flowers, lightly prune after flowering to maximise the number of side shoots as the flowering buds are towards the top.
To produce fewer flowers that are larger prune the plant back hard after flowering by half and remove old or damaged wood.
Pruning can take place in late winter, when all chances of frost has passed or after flowering.
Soil
To produce blue flowers the soil must be acidic with a pH of 5.0 to 5.5. The addition of sulphate of aluminium or sulphate of iron will make the soil acidic.
To produce red to pink flowers a pH of 6.0 to 6.5 is required. The addition of agricultural lime to the soil will make it alkaline.