Azaleas are the defining shrubs of the spring garden — massed flowering in shades of pink, red, orange, white, and purple that can be spectacular when timed well. They are rhododendrons (the line between azalea and rhododendron is botanical, not horticultural) and share the same requirements: acidic soil, good drainage, and dappled shade. In Zone 6b they are reliably hardy with good cultivar selection.
Not typically grown as cut flowers — the individual branches are short-lived once cut and the plants are too valuable to harvest heavily. Grow them for their contribution to the spring garden and as companions to daffodils, hellebores, and bleeding heart.
Powdery mildew
White or grey powdery coating on leaves — usually starting on older growth in humid conditions or when nights cool.
Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.
Botrytis (grey mould)
Grey fuzzy mould on petals and stems, worst in cool wet conditions.
Remove affected parts immediately. Improve air circulation. Avoid overhead watering. Apply copper fungicide if severe.
Crown Rot
Lower leaves yellow and wilt; the base of the rosette turns brown and soft, sometimes with white fungal threads at the soil line. Plants collapse in wet conditions.
Remove and destroy affected plants. Improve drainage and avoid overhead watering. Do not mulch directly against the crown. Space plants for airflow and avoid replanting in the same wet spot.
Azalea Petal Blight
Small watery spots on flower petals that enlarge into brown, slimy patches; blooms collapse and stick to foliage. Worse in warm, wet spring weather.
Remove and destroy infected blooms promptly. Avoid overhead watering. Clear fallen petals from the soil to reduce overwintering spores. Apply fungicide at first bloom if the problem recurs.
Azalea Leaf Gall
New leaves and buds swell into thick, pale green or white fleshy galls that later turn brown and hard. Common in cool, humid spring conditions.
Handpick and destroy galls before they turn white and release spores. Improve air circulation by thinning growth. Fungicide is rarely needed for light infections.
Azalea Lace Bug
Leaf upper surfaces show stippled, silvery-white speckling; undersides carry dark spots of excrement and small clear-winged insects. Heavy feeding bronzes foliage.
Spray leaf undersides with insecticidal soap or horticultural oil when nymphs appear in late spring. Repeat through the season. Site plants in shade, since stressed sun-grown shrubs are hit hardest.