Fixing Leggy Seedlings: Light, Temperature, and Transplanting

Why Zinnias, Cosmos, and Daisies Stretch Indoors

Leggy growth results from insufficient light intensity, excessive heat, or overcrowding.

Solutions

• Light: Keep fluorescent tubes 2–3 inches above seedlings. Run 14–16 hours/day.
• Temperature: After germination, drop to 60–65°F (16–18°C) to slow stem elongation and promote branching.
• Transplant deeply: When moving to 4-inch pots, bury stem up to the first true leaves. Many annuals (tomatoes, zinnias) will root along the buried stem.
• Pinch: After 4th true leaf set, pinch the tip to encourage bushiness.

Pot Size

4-inch pots are fine for short-term holding. If seedlings are crowded, use cell packs or smaller pots first, then step up.

Harden off and move outdoors as soon as weather permits; natural light and wind strengthen stems dramatically.