Azalea Purple Leaves: Phosphorus Deficiency and Correction

Diagnosis: Phosphorus Deficiency

Purple or reddish discoloration on azalea leaves—especially older, upper foliage—is a classic sign of phosphorus (P) deficiency. Cold, wet soils in spring reduce P uptake, even if soil levels are adequate.

Corrective Actions

• Azalea-specific fertilizer (acid-forming, with P) already applied—good start.
• Superphosphate (0-20-0) as supplemental P source if deficiency persists.
• Follow label rates exactly—overfertilizing burns roots.

Other Contributing Factors

• Soil pH too high (azaleas need 4.5–6.0)—test and amend with sulfur if needed.
• Compacted or waterlogged soil—improve drainage/aeration.
• Root damage from planting or pests.

Why Only One Plant?

Microclimate differences (drainage, sun, root zone) can affect individual plants. The healthy one likely has better root conditions.

Monitoring Recovery

New growth should be green. Older purple leaves won't revert but will drop naturally. Retest soil in 6–12 months.