Leaf Issues

Yellowing Leaves

Symptoms: Lower leaves turning yellow and dropping off, starting from the bottom of the plant and working upward. May be accompanied by overall pale appearance and reduced flowering. Common Causes:

• Nitrogen deficiency from inadequate fertilization or nutrient-poor soil
• Overwatering leading to poor oxygen availability to roots
• Natural aging of lower leaves as energy is redirected to new growth and flowers

Solutions:

• Apply a balanced water-soluble fertilizer (10-10-10) every 1-2 weeks during growing season
• Check soil moisture before watering - allow top inch to dry between waterings
• Remove yellowed leaves promptly to prevent disease spread and improve appearance

Prevention: Maintain regular feeding schedule during active growth, ensure proper drainage in containers, and provide adequate spacing for air circulation.

Brown/Crispy Leaves

Symptoms: Leaf edges turning brown and crispy, sometimes with yellow halos. Leaves may curl inward and feel dry to touch. Common Causes:

• Low humidity combined with high temperatures
• Fertilizer burn from over-application or concentrated fertilizer
• Salt buildup in soil from hard water or excessive fertilization

Solutions:

• Increase humidity by grouping plants or using pebble trays in dry climates
• Flush soil thoroughly with clean water to remove salt buildup
• Reduce fertilizer concentration to half-strength if burning continues

Prevention: Use rainwater or filtered water when possible, apply fertilizer to moist soil only, and monitor EC levels in container gardens.

Drooping/Wilting

Symptoms: Stems and leaves lose rigidity and droop despite adequate soil moisture. May recover temporarily in cooler evening temperatures. Common Causes:

• Heat stress during afternoon sun exposure
• Root damage from overwatering or root rot
• Transplant shock after moving or repotting

Solutions:

• Provide afternoon shade during extreme heat (above 85°F/29°C)
• Check roots for rot - trim affected areas and repot in fresh, well-draining soil
• Water deeply early in the morning to help plants cope with heat stress

Prevention: Choose heat-tolerant varieties for hot climates, ensure proper drainage, and acclimate plants gradually to new locations.

Leaf Drop

Symptoms: Sudden dropping of green leaves, often following environmental changes. May affect entire sections of the plant. Common Causes:

• Temperature fluctuations or cold drafts
• Sudden changes in light exposure
• Ethylene gas exposure from ripening fruit or exhaust fumes

Solutions:

• Maintain consistent temperatures between 60-75°F (15-24°C)
• Gradually acclimate plants to new light conditions over 7-10 days
• Keep petunias away from ethylene sources and ensure good ventilation

Prevention: Protect from cold winds, avoid placing near heating/cooling vents, and maintain stable growing conditions.

Growth Issues

Stunted Growth

Symptoms: Plant remains small with shortened internodes, few flowers, and overall compact appearance despite adequate growing time. Common Causes:

• Poor soil quality or compacted growing medium
• Insufficient light for proper photosynthesis
• Root restriction in too-small containers

Solutions:

• Transplant to larger container with fresh, high-quality potting mix
• Move to location receiving 6+ hours of direct sunlight daily
• Apply balanced fertilizer with micronutrients to address deficiencies

Prevention: Start with appropriate container sizes, use quality potting mix, and ensure adequate light from the beginning.

Leggy/Stretching Growth

Symptoms: Long, weak stems with widely spaced leaves. Few flowers and tendency to flop over. Common Causes:

• Insufficient light causing phototropic stretching
• Excessive nitrogen fertilization promoting vegetative growth
• Lack of regular pinching/deadheading

Solutions:

• Pinch stems back by 1/3 to encourage branching and compact growth
• Move to brighter location or supplement with grow lights
• Switch to low-nitrogen, high-phosphorus fertilizer to promote flowering

Prevention: Provide full sun exposure, pinch young plants regularly, and maintain proper fertilizer ratios throughout the season.

Pest Problems

Aphids

Identification: Small, soft-bodied insects in green, black, or white colors clustered on new growth and flower buds. May see sticky honeydew residue. Damage Signs: Curled, distorted leaves and stunted new growth. Sticky coating on leaves below infestations. Treatment:

• Spray with insecticidal soap solution every 3 days until controlled
• Release ladybugs or lacewings for biological control
• Use neem oil spray for persistent infestations Prevention: Inspect new plants before introducing, avoid over-fertilization with nitrogen, and encourage beneficial insects with diverse plantings.

Tobacco Budworms

Identification: Green or reddish caterpillars up to 1.5 inches long, often found inside flower buds or eating petals. Damage Signs: Holes in flower petals, damaged buds that fail to open, frass (droppings) on leaves. Treatment:

• Hand-pick caterpillars in early morning when they're most active
• Apply Bacillus thuringiensis (Bt) spray weekly during peak season
• Use spinosad-based insecticides for severe infestations Prevention: Choose budworm-resistant varieties, remove spent flowers promptly, and monitor regularly during warm months.

Spider Mites

Identification: Microscopic pests causing stippled, bronze appearance on leaves. Fine webbing visible in severe cases. Damage Signs: Yellow speckling on leaves, eventual bronzing and leaf drop. Webbing between stems and leaves. Treatment:

• Spray forcefully with water to dislodge mites every other day
• Apply miticide specifically labeled for spider mites
• Use horticultural oil or insecticidal soap for organic control Prevention: Maintain adequate humidity, avoid dusty conditions, and inspect undersides of leaves regularly.

Disease Issues

Botrytis Blight (Gray Mold)

Symptoms: Gray, fuzzy mold on flowers and leaves, especially during humid conditions. Brown spots on petals that expand rapidly. Causes: Fungal infection thriving in cool, humid conditions with poor air circulation. Treatment:

• Remove all affected plant parts immediately and dispose in trash
• Apply fungicide containing chlorothalonil or copper
• Improve air circulation and reduce overhead watering Prevention: Space plants adequately, water at soil level, and remove spent flowers before they become moldy.

Root Rot (Pythium/Phytophthora)

Symptoms: Wilting despite moist soil, yellowing leaves, and stunted growth. Dark, mushy roots with foul odor. Causes: Waterlogged soil conditions promoting fungal growth, often in heavy or poorly draining soils. Treatment:

• Remove plant from soil and trim all affected roots with sterile scissors
• Treat remaining roots with fungicide drench
• Repot in fresh, sterile, well-draining potting mix Prevention: Ensure excellent drainage, avoid overwatering, and use disease-free potting media.

Root Problems

Root Rot

Symptoms: Plant wilts even when soil is moist, leaves yellow and drop, growth stops. Foul smell from soil. Identification: Roots appear brown or black instead of white, feel mushy, and may fall apart when touched. Treatment:

• Remove from pot and wash roots gently to assess damage
• Cut away all diseased roots with sterilized scissors
• Replant in fresh soil with added perlite for drainage Prevention: Use pots with drainage holes, water only when top inch of soil is dry, and ensure proper soil structure.

Root Bound

Symptoms: Stunted growth despite proper care, water runs through pot quickly, roots visible at drainage holes. Identification: Dense mat of circling roots when removed from pot, little soil visible among root mass. Treatment:

• Transplant to container 2 inches larger in diameter
• Gently tease apart circling roots before replanting
• Trim excessively long roots to encourage new growth Prevention: Repot annually or when roots fill container, choose appropriate pot sizes from the start.

Environmental Stress

Temperature Shock

Symptoms: Sudden wilting, flower drop, or leaf discoloration following temperature extremes. Causes: Exposure to temperatures below 50°F (10°C) or above 90°F (32°C), rapid temperature changes. Treatment: Move to protected location, remove damaged tissue, and allow gradual recovery with consistent care. Prevention: Harden off transplants properly, provide shade during heat waves, and protect from cold snaps.

Humidity Issues

Low Humidity Symptoms: Crispy leaf edges, flower bud drop, increased spider mite susceptibility. High Humidity Symptoms: Fungal diseases, soft rot, reduced flowering. Solutions: Use humidity trays for dry conditions, improve air circulation for high humidity. Prevention: Monitor humidity levels, space plants properly, and choose appropriate varieties for your climate.

Light Stress

Too Much Light: Bleached or scorched leaves, wilting during hottest part of day despite moist soil. Too Little Light: Leggy growth, few flowers, pale green leaves. Solutions: Provide filtered shade during intense afternoon sun, or move to brighter location if insufficient. Prevention: Understand specific variety's light requirements and position accordingly from planting.

Quick Diagnostic Guide

Emergency Symptoms

When to Seek Help

• Plant continues to decline despite treatment attempts
• Unusual symptoms not matching common problems
• Disease spreading rapidly to other plants

Prevention Checklist

• [ ] Plant in well-draining soil or quality potting mix
• [ ] Provide 6+ hours of sunlight daily
• [ ] Water at soil level to keep foliage dry
• [ ] Fertilize regularly with balanced plant food
• [ ] Deadhead spent flowers to prevent disease
• [ ] Monitor for pests weekly during growing season

Recovery Timeline

Week 1: Remove damaged tissue, adjust care practices, begin appropriate treatment Week 2-3: New growth should emerge if roots are healthy, continue monitoring and treatment Month 1+: Full recovery with vigorous growth and flowering if problems are resolved

Remember: Most Petunia problems are preventable with proper care. When in doubt, adjust watering first, then light conditions.