A young plant in its first stage of development after germination, characterized by cotyledons (seed leaves) and fragile growth.
In plain terms
Once a seed sprouts, it's a seedling—a young plant with tiny leaves and delicate stems. Seedlings need careful conditions: consistent moisture (not waterlogging), bright light, and protection from temperature extremes. They're vulnerable to damping off (fungal disease) and pests. After developing true leaves (leaves that look like adult plant leaves), seedlings are ready to harden off and transplant.
Why this matters
Understanding seedling needs prevents common problems like damping off or leggy growth. Proper seedling care sets up transplants for success.
In practice
Examples
Tomato seedling with cotyledons only; looks fragile but normal; light and warmth support growth.
Seedling with true leaves developing; ready to thin or pot up.
Leggy seedling (tall, weak, pale); insufficient light; moving under grow lights improves it.
Crowded seedling tray; seedlings compete for light and water; thinning improves survival.
Practical applications
Provide bright light immediately after sprouting (grow lights 12-16 hours daily).
Keep soil consistently moist but not waterlogged (damping off risk).
Thin crowded seedlings early to prevent competition and disease.
Provide gentle air circulation with small fan to strengthen stems.
Pot up into larger containers once true leaves appear.