Sprouted, then stopped

First, the pause is partly normal

After cotyledons open, lettuce spends one to two weeks building roots before top growth accelerates. A seedling that looks unchanged for ten days is often fine. The problem starts when the pause runs past two weeks, the leaves stay small and pale, or the stem darkens at the base.

1. Light (most common)

Cotyledons can open on stored energy; real leaves cannot. If the seedling is on a windowsill getting two or three hours of weak winter light, it has nothing to build with. Move it to the brightest spot you have, or add a lamp for 12–14 hours a day.

2. Damping off

A dark, pinched stem at soil level and a seedling that collapses is a fungal problem, not a nutrient one. It comes from wet, still, warm conditions and crowded trays. There is no cure — remove affected cells, water from below, improve airflow, and sow thinner next time.

3. Waterlogged roots

Lettuce roots need oxygen. A tray sitting in water looks healthy from above and stalls below. Drain saucers, water when the surface just dries, and never leave seedlings standing in a puddle.

4. Temperature

Cold soil below about 10 °C slows everything to a crawl; hot soil above 24 °C pushes the plant toward flowering instead of leaves. Around 18 °C is the sweet spot.

5. Hunger and crowding

Seed compost has enough nutrients for about two to three weeks. After that, seedlings in the same cell compete and stall. Prick out into fresh compost, or feed weakly. Crowding on its own will stall a tray even with perfect light.

What "normal" looks like

Germination is typically 7–10 days. The fastest varieties in the catalogue reach harvest in about 40 days; slower hearting types take 60–90. If you are at day 30 with four small leaves, light and crowding are the two things to check first.

Fastest varieties in the catalogue

The short version

Check light first, then whether the roots are sitting in water, then whether the tray is overcrowded. Those three account for almost every stalled lettuce seedling.

Questions

All 110 lettuce varieties →  ·  Browse the catalogue