How to grow hydrangea
Overview
Hydrangea macrophylla is a deciduous shrub grown for its large, showy flower heads in shades of blue, pink, or white. It provides structure and texture in the garden, linking bolder feature plants. Key to success is understanding that flower colour is influenced by soil pH.
Varieties
- Endless Summer — A reblooming variety that flowers on both old and new wood, popular in temperate Australia.
- Nikko Blue — Classic blue mophead, reliable in cooler zones with consistent blue colour.
- Pia — Compact dwarf hydrangea, ideal for small gardens and pots in subtropical areas.
Soil Preparation
Hydrangea prefers rich, well-drained soil with a pH between 5.5 and 6.5 for best colour. Add organic matter like compost or well-rotted manure before planting. Ensure good drainage; if soil is heavy clay, raise beds or add gypsum.
Growing Guide
Plant hydrangea in a position with morning sun and afternoon shade, especially in warmer climates. Space plants 1–1.5 m apart. Dig a hole twice as wide as the root ball and amend with well-rotted organic matter. Water deeply after planting and maintain consistent moisture, especially during flowering. Avoid planting in heavy clay or waterlogged soil.
Care
Feed in spring and autumn with a balanced slow-release fertiliser. Prune after flowering, cutting back to just above a pair of healthy buds. Remove dead wood and thin crowded stems in winter. For blue flowers, apply aluminium sulphate to acidify soil.
Companion Planting
Good companions include camellias, ferns, and hostas, which enjoy similar conditions. Avoid planting near large eucalypts or other trees with aggressive, water-hungry roots that will compete for moisture.
Common Pests & Risks
Aphids, mites, and powdery mildew are common. Treat aphids and mites with a strong spray of water or insecticidal soap. Improve air circulation around plants to reduce powdery mildew. Avoid overhead watering.
Harvesting
Hydrangea flowers are harvested for cut flowers or drying. Cut stems when the flowers are fully open and the petals feel papery. For drying, hang upside down in a cool, dark place. Harvest in the morning when the plant is turgid.
Troubleshooting
Yellow leaves: often due to iron deficiency in alkaline soil; treat with iron chelate. Brown leaf edges: usually from too much sun or wind; move to more sheltered spot. No flowers: often caused by pruning at wrong time or frost damage; prune only after flowering. Powdery mildew: improve air circulation and avoid overhead watering. Wilting: check for dry soil; water deeply if needed.