How to grow azalea
Overview
Azalea (Rhododendron indicum) is a compact, evergreen shrub grown for its dense foliage and prolific spring blooms. It provides garden structure and links bolder feature plants, thriving in acidic, well-drained soil with protection from hot afternoon sun.
Varieties
- Rhododendron indicum 'Balsaminiflorum' — Compact, double pink blooms; excellent for small gardens and pots in temperate zones.
- Rhododendron indicum 'Kurume' hybrids — Dwarf, dense habit with masses of small flowers in pink, red, or white; ideal for cool and temperate climates.
- Rhododendron indicum 'Satsuki' hybrids — Late-flowering (Nov–Dec) with large, ruffled blooms in pastel shades; popular in subtropical and Mediterranean gardens.
Soil Preparation
Azalea requires acidic soil with pH 4.5–6.0. Before planting, test pH and amend with sulfur or iron chelate if needed. Incorporate well-rotted pine bark or peat moss to improve drainage and acidity. Ensure the site drains freely — raised beds or mounds are ideal for heavy clay.
Growing Guide
Plant azalea in a sheltered position with dappled morning sun and afternoon shade. Space 60–90 cm apart for a dense hedge or 1–1.5 m for specimen growth. Dig a hole twice the width of the root ball, backfill with native soil mixed 50:50 with acidic compost, and water in well. Keep the root zone consistently moist but never waterlogged; apply a 5 cm layer of pine bark or leaf mulch to cool roots. Avoid planting near concrete or limestone paths that can raise soil pH.
Care
Feed with an acid-specific fertiliser (e.g., Osmocote for Azaleas) in early spring and again after flowering. Prune lightly after bloom to shape and remove spent flowers; avoid heavy pruning after midsummer as it sets next year's buds. Keep mulch 5 cm away from the stem base to prevent collar rot.
Companion Planting
Pair azalea with camellias, gardenias, and ferns for a cohesive shade garden. Avoid planting near eucalypts or grevilleas, which can compete for moisture and raise soil pH. Underplant with clivia or hellebores for year-round interest.
Common Pests & Risks
Azalea lace bug causes stippled, silvery leaves; treat with horticultural oil or systemic insecticide in early spring. Root rot (Phytophthora) occurs in poorly drained soil — prevent by raising beds and avoiding overwatering. Azalea gall (Exobasidium) distorts new growth; remove affected shoots promptly and dispose of in bin, not compost.
Troubleshooting
Yellow leaves with green veins: iron deficiency (chlorosis) — apply iron chelate or lower soil pH. Brown leaf edges: salt burn or dry roots — flush soil with water and improve mulch. Stunted growth: root rot or poor drainage — lift plant, trim rotted roots, and replant in raised bed. Lace bug damage: stippled leaves — spray with neem oil or systemic insecticide in spring. Bud drop: sudden temperature change or dry spell — maintain consistent moisture and mulch.