Common Seedling Problems

While producing seedlings indoor can be a truly reinvigorating activity, especially for those of us who as still dealing with the last throes of winter, it can quickly become thoroughly exhausting when things don’t turn out as planned. Here are a few problems you may encounter, how to identify and deal with them.

Damping-Off

Seedlings fall over and appear water-soaked at the base of the stem. The affected area might look slimy or mushy. Seedlings might die before or shortly after emerging.

• Cause: A fungal disease affecting seedlings, causing them to rot at the soil line and collapse.
• Solution: Use sterile potting mix and containers, avoid overwatering, and ensure good air circulation. Prevention is key.

Leggy Seedlings

Seedlings have unusually long stems, often weak and thin, struggling to stand upright. They may lean towards a light source if it’s not directly overhead.

• Cause: Insufficient light causes seedlings to stretch towards the light source, resulting in weak, elongated stems.
• Solution: Ensure seedlings receive enough bright, direct light each day. Using artificial lights is highly recommended.

Leaf Discoloration (Yellowing or Browning)

Yellowing often starts with the older, lower leaves. It can indicate overwatering, underwatering, or nutrient deficiencies (commonly nitrogen). Tips or edges of leaves can turn brown.

• Cause: Nutrient deficiencies, overwatering, or underwatering.
• Solution: Ensure proper watering practices and use a small amount of organic fertilizer. If overwatering is the issue, let the soil dry out a bit more between waterings.

Wilting

Leaves droop, look limp, and the plant loses its rigidity. Wilting can occur with both dry and waterlogged soils.

• Cause: Underwatering, overwatering, or root damage.
• Solution: Adjust watering practices. Check the roots for damage or rot and repot if necessary, using fresh, well-draining soil.

Pest Infestations

Visible insects or mites on the plant, under leaves, or on the soil. Look for honeydew (sticky residue), webbing, or leaf damage like holes, spots, or chewed edges.

• Cause: Small insects feeding on the seedlings, often found on the underside of leaves.
• Solution: Use a gentle stream of water to knock pests off, apply insecticidal soap, or introduce natural predators.

Mold or Fungus on Soil

White, green, or black mold growth on the soil surface. You may also notice a musty smell.

• Cause: Too much moisture and poor air circulation.
• Solution: Reduce watering, increase airflow around the seedlings, and remove any visibly moldy soil. Consider using a fungicide if the problem persists.

Leaf Spot Diseases

Circular or irregular-shaped spots on leaves, which may be brown, black, yellow, or red. The center of the spot might fall out, leaving a hole.

• Cause: Fungal or bacterial infections causing spots on leaves.
• Solution: Remove affected leaves, avoid wetting foliage when watering, and ensure good air circulation. Fungicides or bactericides can be applied as needed.

Nutrient Burn

Leaf tips and edges turn brown or black and appear burned. This problem often starts with the lower leaves and moves upward.

• Cause: Over-fertilization leading to burned or crisped leaf edges.
• Solution: Flush soil with water to remove excess fertilizer, then wait before fertilizing again, using a weaker solution.

Temperature Stress

Too Cold: Stunted growth, purpling of leaves or stems, wilting.

Too Hot: Leaves curl upwards, dry out, or show signs of sunburn (bleached spots).

• Cause: Too high or too low temperatures.
• Solution: Move seedlings to a more suitable environment. Use grow lights and heating mats if too cold, or increase ventilation and shading if too hot.

Managing these issues often involves a balance of preventative measures and timely interventions. Regular monitoring and adapting to the needs of your seedlings as they grow will help ensure their healthy development.

Excess Light

Intense artificial sources or prolonged direct sunlight can lead to stress and growth issues in seedlings, evident through signs like leaf scorching, fading or bleaching, and wilting.

• Causes: Seedlings too close to artificial lights or not properly acclimatized to direct sunlight.
• Solutions: It’s essential to adjust the distance of artificial lights, use timers to control exposure, and provide shade to manage direct sunlight.

Purple Leaves

Seedlings displaying purple leaves and stems, often on the underside or along the veins, accompanied by slowed or stunted growth.

• Causes : Phosphorus deficiency, usually exacerbated by cold soil temperatures that affect nutrient uptake. In some cases, it’s a natural genetic trait of the plant, and excessive light can also contribute by stressing the plant and increasing nutrient demands.
• Solutions: Warming the soil and applying phosphorus-rich fertilizers can correct the issue. For seedlings with genetic traits displaying purple, no action is necessary. Managing light exposure and maintaining stable environmental conditions are crucial for preventing stress-induced coloration.

---

Prevention is key! Use sterile potting mix and containers and ensure good drainage and air circulation. Provide sufficient light, monitor water intake and apply balanced, mild fertilizers to prevent nutrient imbalances. Inspect regularly for pests and diseases. Be careful of any sudden changes in the seedlings environment which could cause them stress. Relax and enjoy, though you may run into problems, you can always try again or buy seedlings from a garden center when all else fails!