When your lavender seedlings die suddenly without warning, damping off fungus is almost always the cause. This disease strikes fast and kills plants overnight. Poor drainage and too much water make the problem worse by giving fungal spores the wet conditions they need to grow.
I lost a whole tray of thirty seedlings to this disease my first year growing lavender. They looked perfect one evening and lay flat on the soil the next morning. I dug one up to check and found a mushy brown spot right where the stem met the dirt. That's when I learned about damping off lavender.
NC State Extension warns about deadly soil fungi that attack young lavender plants. These include Fusarium and Phytophthora species that live in dirt. They wait for wet conditions to strike your seedlings. Wet soil and poor airflow give them everything they need to kill your plants fast.
You'll know damping off hit when your seedlings fall over with pinched stems at soil level. The base looks water-soaked and thin. Healthy leaves may still look green even as the plant dies from below. Once you see these signs, that plant is gone and you need to act fast to save the rest.
The main lavender seedling death causes beyond damping off include too much water and not enough air. Soggy soil invites disease to your plants. Stagnant air lets moisture sit on stems and leaves. Both conditions help fungi spread from plant to plant across your seed trays.
Start with sterile seed starting mix instead of garden soil to prevent problems. Fresh mix from a sealed bag has no fungal spores hiding inside. Old or open bags can pick up contamination. Always use clean containers and wash your hands before handling seedlings to avoid spreading disease.
Set up a small fan to blow gentle air across your seed trays at all times. This keeps surfaces dry and stops fungi from taking hold. Water only in the morning so soil can dry during the day. Skip watering if the top of the soil still feels moist from the day before.
Remove any sick plants from your trays right away along with the soil around them. Fungal spores spread fast to nearby seedlings if you wait. Some growers spray with diluted chamomile tea as a natural fungicide. The tea helps prevent infection but won't cure plants already showing signs of damping off.
Read the full article: How to Grow Lavender From Seed Successfully
