Yellow Leaves with Green Veins on Container Perennials: Iron Chlorosis from Overwatering and Overfertilizing

Diagnosis: Iron Chlorosis Induced by Cultural Practices

Yellow leaves with green veins (interveinal chlorosis) on Agastache, Sweet William, and Zauschneria in containers — despite iron, nitrogen, and fungicide applications — points to root dysfunction from overwatering and/or overfertilizing.

Why It Happens

• Osmocote + frequent watering = salt buildup and root burn.
• Agastache prefers lean, dry conditions — opposite of container coddling.
• Wet soil reduces oxygen, impairing iron uptake even if iron is present.

Recovery Plan

1. Stop all fertilizer.
2. Water only when top 1–2 inches of soil are dry.
3. Ensure pots drain freely — elevate, add perlite if needed.
4. Repot in fresh, lean mix (1 part compost : 2 parts sand/pumice : 1 part peat) if roots are mushy.

Plant-Specific Notes

• Agastache: Thrives on neglect. Full sun, sharp drainage, minimal water/fert.
• Sweet William: Biennial; may have completed life cycle.
• Zauschneria: Desert plant — hates wet feet.