Too little light (leggy plants)

About

Seedlings on a windowsill and houseplants in dim rooms grow tall, thin and pale as they reach for light. More light fixes new growth, though stretched stems stay stretched.

Also called low light, light deficiency, lack of light, insufficient light, not enough light, leggy seedlings, leggy growth, etiolation, stretched seedlings

How to recognize it

Symptoms

Long, thin, weak stems with wide gaps between leaves, leaning toward the window. Leaves are small and pale green to yellow, older leaves yellow and drop, variegated leaves turn plain green, and flowering plants stop making buds.

Often confused with

Nitrogen shortage also yellows older leaves, but plants aren't stretched.

Worse when

Windowsills in winter, north windows or spots far from windows, fluorescent lights hung too high or old tubes, and seedlings crowded into one cell.

How it spreads

It does not spread.

When

Late winter seed starting; houseplants in fall and winter.

What to do, gentlest first

This is not an infection, so sprays for diseases won't help. Fix the cause below.

1. Use grow lights close and long Prevent

   Keep fluorescent or LED grow lights a few inches above seedlings (Illinois says 2 to 4 inches for fluorescents; UMN says 4 to 6 inches) and raise them as plants grow. UMN suggests 16 to 18 hours of light a day for seedlings.

   Fluorescent tubes dim with age; replace them after several seasons.

2. Thin seedlings Prevent

   Sow just a few seeds per cell and thin to one so seedlings don't compete for light.

3. Move and turn houseplants By hand

   Move plants closer to the brightest window (south is brightest, north is lowest) and turn them often so they grow evenly. Add a grow light in winter.

   Move plants into much brighter light gradually, or the leaves can sunburn (see Leaf sunburn).

Plants it affects

Broccoli, Cabbage, Eggplant, Lettuce, Pepper (sweet and chili), Tomato