Azalea

About Azalea

Azaleas are acid-loving shrubs in the rhododendron genus that cover themselves in funnel-shaped flowers in spring. Evergreen azaleas (Southern Indica, Kurume, Satsuki, Glenn Dale and the reblooming Encore series) are Southern favorites, while deciduous native azaleas such as flame, Florida, pinxterbloom and plumleaf azalea feed hummingbirds, butterflies and bees. All parts are poisonous.

NC State lists azaleas and rhododendrons for zones 4-8; Florida and plumleaf azaleas grow to zone 9, and the University of Minnesota's Northern Lights azaleas have flower buds hardy to about -30 to -45 F.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Filtered shade, like under pines, suits them best; too much sun invites lace bugs (Clemson). Water new plants deeply, 6-8 inches down, in dry spells, and keep 2-3 inches of pine straw or bark mulch a couple of inches from the stems (Clemson).

Soil

Acid, well-drained soil rich in organic matter; roots are shallow and rot in wet ground, and high pH causes yellow leaves with green veins (Clemson). Native azaleas dislike dense clay (NC State).

Plant in acid (pH 4.5-6.0), well-drained soil rich in organic matter; set plants high rather than deep, since the shallow roots rot in wet soil (Clemson).

Feeding

• Late spring to early summer, after new growth appears: acid-forming azalea fertilizer with about a 2-1-1 ratio (for example 10-5-4), slow-release. Clemson: about 1 lb of actual nitrogen per 1,000 sq ft (up to 2 lb with slow-release products), spread over the root zone and watered in; follow a soil test.

Never fertilize in late fall; it delays dormancy and invites cold injury (Clemson). Yellow leaves with green veins usually mean the pH is too high.

Harvest

Azaleas bloom from early spring to midsummer depending on the kind; plumleaf azalea blooms in late summer and Encore azaleas bloom in spring and again in fall. Prune just after flowering in spring so you don't cut off next year's buds (Clemson, NC State).

Varieties (22)

Pests to watch for

Twospotted spider mite, Aphids, Mealybugs, Scale insects, Thrips, Whiteflies, Sawflies (garden sawflies), Lace bugs (azalea and chrysanthemum lace bugs), Four-lined plant bug, Granulate ambrosia beetle, Foliar nematodes

Diseases and problems

Petal blight, Leaf gall, Phytophthora root rot, Leaf spot, Dieback, Iron chlorosis, Leaf scorch, Black walnut toxicity, Soil pH problems

In the kitchen

Safety: All parts, including the nectar, contain grayanotoxins; NC State rates the risk from small amounts as low, but don't eat any part.

Pets: Toxic to dogs, cats and horses (ASPCA): grayanotoxin can cause vomiting (not in horses), diarrhea, weakness and heart failure.