Lavender Decline in Tropical Climate: Phytophthora Risk, Watering, and Soil Mix Adjustments

Lavender Decline in Tropical Climate: Phytophthora Risk, Watering, and Soil Mix Adjustments

Lavender in Pekanbaru, Indonesia (tropical rainforest, 23–30°C, 60–98% humidity) has grey young leaves. Copper fungicide didn't help. Soil mix: alluvial soil, sand, compost, pebbles (1:1:1:1). Tried full sun → leaves browned.

Dead young leaves

Lavender plant

Lavender seedling

Diagnosis

1. Overwatering / poor drainage: Lavender hates wet feet. Saucer water = death.
2. Phytophthora root rot: Fatal, spreads fast in wet soil. If multiple plants, discard infected one.

Immediate Actions

• Empty saucer completely after watering.
• Increase sand in mix (rinse if salty).
• Partial shade (2 hrs sun)—equatorial sun is too intense.
• Maximize light, minimize water.

If No Improvement in Days

Discard plant to protect others. Phytophthora destroys whole nursery batches.

Fertilizer (Nursery Practice)

Time-release (Osmocote) 2–3×/year, higher phosphorus (e.g., 5-10-5).

Lavender in the tropics is a challenge—drainage and shade are critical.