What stretch looks like
Cause
Too little light, light that is too far, or air that is too warm
Shape
A long, slender shoot that cannot hold the crown and becomes top-heavy
Read it
A skinny stem is a light problem first, not a nutrient puzzle
Fix going forward
Move lamps closer or add intensity, and cool the air if it is driving stretch
Support what already stretched
Stakes
Toothpicks, chopsticks, skewers, or thin bamboo keep a weak stem upright
Bury
At transplant, set a stretched stem a little deeper so the plant sits stable
Compress
After backfill, gently firm the mix so the stem does not wobble
Do not snap
Support first. Do not try to fold a woody lean back into place
Air and handling
Circulation
Moving air helps a stem thicken and keeps the surface from staying wet
Pets
Mice, birds, dogs, and cats eat sprouts. Use a barrier
Hitchhikers
Indoor-outdoor pets can also walk insects into a seedling tray
Fridge hold
If you cannot plant yet, a moist bag in the crisper above 40 F (4 C) can pause growth for a week or more. Never freeze
Hardening to outdoor sun
Shade first
Set indoor seedlings in shade or under screen before full sun
Five days
Step them into brighter light over about five days
Anti-transpirant
A leaf spray can slow water loss while new sun leaves form
New leaves
Leaves grown in sun build longer palisade cells and handle UV better than indoor leaves dumped outside
Started outdoors
Seedlings that germinate outside adapt to bright sun more easily