Guide To Help Others Germinate Lettuce Seeds Successfully
Lettuce seeds can be one of the most difficult seeds to uniformly germinate due to thermodormancy and photodormancy. Lettuce will not germinate well if temps are too high or if seeds are in the dark. For a near 100% germination rate this is what I do.
1) Make sure lettuce seed is from this year. Lettuce seed loses its vigor within a year. This is often one of the unforeseen problems that handicap one's efforts right from the start.
2) If you make your own soilless mixes this is the recipe I use.
A) 1/4th perlite, 1/2 fine grade horticultural vermiculite, 1/4 peat moss.
If you don't make a soilless mix then you should just buy an organic potting mix that contains peat moss and perlite.
3) Keep temperatures between 70-85 degrees. Lettuce seed requires daily temps that are on the cooler side 55-75 is good to prevent bolting. To germinate the seeds however, the best temperatures are between 70-85. At these temps with the good seed and proper light I can get 10% germination in 18 hours and 98% germination in 48 hours.
4) Light is the most overlooked part of growing lettuce. Since lettuce is photodorment it will not germinate in the dark. It seems very difficult to think of a seed successfully germinating on the surface where the air is dry and the seed can dry out quickly. But that can be pretty easily overcome. For light sources you will want to place the plug tray, or whatever else you have used to put your soilless mix in under fluorescent lighting within an inch of the bulb or in a south facing window where the seeds get sunlight at least 3-4 hours a day.
With your plug tray or flats, make sure the soil has been pressed down smoothly. Sprinkle lettuce seeds on top of the soil surface. Lightly press the seeds into the soil. Use a spray bottle or a garden hose on mist setting. Thoroughly soak the soil and seeds gently.
It is a common understanding of most growers not to over soak your soilless medium when germinating seeds. Generally this practice is applied because many seeds take 5-10 days to germinate and molds that can cause diseases such as the dreaded damping-off will have a much better chance at establishing themselves well before the seed can break the surface.
Lettuce is the exception. You soak the seed and you place saran wrap over the flat or tray you have the seed in. Place it under the light, keep temps between 70-85. After 1 day check the soil to make sure it is still saturated. If it looks to be drying up even a little, soak the entire surface again and recover. After 48 hours, open the flat or tray again and closely look at the lettuce seed. You should notice most seeds have split at the base where a very tiny root is breaking through. If you see that more than half of the seeds are like that, take the saran wrap off, spray with water to keep the surface wet while the seeds dig their roots into the soil. Once the roots are established enough after 3-4 days you can begin letting the soil dry out a little bit before watering again.
By allowing the soil to dry out a bit you will have changed the environment your seeds were in and if there was any fungus growing that could potentially damage your seedlings you will have slowed or stopped its growth by allowing the soil surface to dry out a bit. Now all that is left is to lightly water, keep under light, and wait 4-6 weeks to transplant into your garden. Don't forget to harden lettuce off. Even though it is a cold crop that can tolerate light frosts if it was grown in the house it still needs to be acclimated to the outdoors.