Flowering Plum Sudden Defoliation: Overwatering Root Rot Risk

Case Summary

4-yr-old flowering plum, Redding CA (hot summers). Flood-irrigated every 3 days. Leaves fell green 2 months ago; now dried, tree nearly bare. Mixed bed with crepe myrtle, mock orange, groundcovers.

Diagnosis: Root Rot from Overwatering

• Flooding every 3 days = chronic saturation.
• Roots need oxygen—anaerobic soil = root death → Phytophthora/Pythium invasion.
• Symptoms: green leaf drop (hydraulic failure) → desiccation.

Soil Check

• Dig 6–8" near root ball: sour smell? gray/blue soil? = anaerobic.
• Roots: black, mushy, slough off = rot.

Immediate Actions

1. Stop Flooding: Switch to deep soak 1×/week (adjust for heat).
2. Check Trunk Base: Clear mulch; look for loose bark, cankers.
3. Improve Drainage: If possible, aerate soil vertically (auger holes) without root damage.
4. Fungicide? Subdue Maxx (mefenoxam) drench — pro only, marginal if advanced.

Bedmate Considerations

Crepe myrtle, mock orange, myoporum, dragon's blood have lower water needs. Separate irrigation zones or replant plum in well-drained spot.

Plum on 3-day flood schedule in Redding heat = guaranteed root rot. Immediate irrigation change is only hope.