Here’s the science-y part, but I’ll keep it light. Lettuce seeds have a built-in thermometer in their little seed coats. When it’s too warm, their internal chemistry says, “Nope, too risky to grow.” They go into a sort of seed hibernation called thermo-dormancy.
The secret trick? Pre-chill your seeds. Pop them in the fridge for 24 to 48 hours before planting. It tricks them into thinking winter just ended. They wake up super enthusiastic. “Oh, it’s spring! Let’s go!”
Lettuce Germination at Harry Brawner blog
Another pro move: plant shallow. Like, barely a quarter-inch deep. Lettuce needs light to trigger germination. Buried too deep, they’re just sleeping underground. Not a good look.
Varieties—They’re Not All the Same
Not all lettuce is created equal. Butterhead and Loose-leaf types are the speed demons. You can see sprouts in 3 to 4 days if conditions are perfect. Romaine? A little slower, maybe 7 to 10 days. Iceberg is the drama queen—easy 10 to 12 days, even in good soil.
Ever grown Mesclun mix? That stuff germinates like it’s got a plane to catch. 2 to 3 days, and suddenly you have a tiny green party. It’s almost suspicious.
