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.
Petal blight
Flowers develop small watery spots that rapidly enlarge into soft brown blotches, collapsing the bloom into a slimy mass that clings to the plant instead of dropping cleanly.
Remove and destroy infected blooms and fallen petals, and clear old mulch beneath the plant where the fungus overwinters. Avoid overhead watering; in wet springs a preventive fungicide at bud break helps where it recurs.
Leaf gall
Leaves, buds, or young shoots thicken into pale green, reddish, or whitish fleshy galls that later turn white with a powdery spore bloom before browning.
Pick off and destroy galls before they turn white and shed spores. Improve air circulation and avoid overhead watering in spring. The damage is largely cosmetic and rarely needs fungicide.
Azalea Lace Bug
Stephanitis pyrioides →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.