Yellowing St. Augustine After Liquid Iron: Diagnosis Before Reapplication

Homeowner applied liquid iron to dry St. Augustine; rain within 12 hours. No improvement after a week. Asks about reapplication.

Iron Response Time

Iron greening takes 2–4 weeks. One week is too soon to judge. Do NOT reapply yet—excess iron can toxicity.

Root Cause Analysis

• High pH (>6.5): Iron unavailable. Soil test needed. Target pH <6.0 for St. Augustine.
• Fungal/viral disease: Yellowing is a symptom. Tissue analysis identifies pathogen.
• Insect pests: Chinch bugs, grubs. Soil/plant analysis needed.

Action Plan

1. Wait 3–4 weeks for iron response.
2. Get soil test (pH, nutrients).
3. If no improvement, submit tissue sample for disease diagnosis.
4. Reference: TAMU St. Augustine Problems

Treat the cause, not the symptom. Iron is a band-aid if pH or disease is the real issue.