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Guide To Help Others Germinate Lettuce Seeds Successfully

Posted by soulreaver 6b (My Page) on
Tue, Feb 19, 13 at 8:35

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.

Final preparation.

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.


Follow-Up Postings:

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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

Lettuce is one of the easiest of seeds to germinate and to grow. I can not prove it, but they seem to be 100% in my experience. Transplanting is also fool proof, they tolerate bare rooting without missing a beat. Even the seedlings I throw away, grow like weeds, just laying on top of the soil. Al


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

My post was for amateur gardeners or people who haven't planted lettuce before. And lettuce may be easy for you to germinate because you already understand the mechanics of seed germination but it is not easy for someone who isn't aware of how lettuce seed works. Just like math is easy for a physicist and not a painter, difficulty of anything is relevant to experience and understanding.

But thanks for your pointless post trying to undermine me or interject yourself as the focus of this thread when I was just trying to give a little useful information to others who might want it.


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

I tried a few seeds of 6 different types of lettuce a couple of weeks ago. 3 types germinated quickly at 100% or near, 1 type Germinated at about 50% and 2 types didn't germinate at all.

Some of the seed was from last year, some from this year, but it was this year's seed that didnt germinate.

So...........my guess is that some lettuce is easier than others.


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

thanks for the info. even tho i have been growing lettuce for years, i didn't realize that you needed to soak the soil and keep the seed in light. i just grew it like everything else and prob had about 70% germination. i will try for better this year. any hints for keeping the plants indoors for indoor harvest? just keep picking the larger leaves? at what size do you transplant and how big a pot is needed?


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

Thank you soulreaver. This is good and useful information.


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

You're welcome HayBerry.

Mandolls do you remember the conditions those seeds were planted under?

Terry, it depends on the lettuce type but I assume you are talking about loose leaf types and not head types. In that case if you want a continued harvest don't take more than 25-50% of the plants vegetative mass every week. Outer leaves should be under 4 inches for best flavor.

If you take too much at once the plant will get stressed. If you keep the plant small by taking the outer leaves on a weekly basis and keep the plants away from temps above 80 degrees you should be able to harvest the same lettuce for 4-6 weeks. All lettuce will eventually try to bolt around that time regardless of how well you take care of it.

Lettuce is a good plant to grow under fluorescent lights indoors. You will actually have better production under a light 14 hours a day than being in direct sun for 3-5 hours in a south facing window because lettuce prefers scattered light over direct sunlight especially when the temperatures get above 70 degrees.

Another thing you can do, if you see any of your lettuce plants starting to bolt, at the very first sign, or even if it is week 5 or 6 and nothing had bolted yet you can take a couple days to harden off your plants, then leave them all outside for a night if the temps will be around 34-45. Light frost causes lettuce and other leafy greens to taste sweeter because the plant produces more sugars to prevent tissue damage from the cold. The next day you can harvest everything and it will taste better.

Also always cut leaves or harvest heads in the morning before it gets warm. It keeps the plants crisper and it will help them last longer in the fridge if you don't plan to eat them right away.


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

"Mandolls do you remember the conditions those seeds were planted under?"

I germinated them inside, in a domed tray, sitting on top of fluorescent lights. The lights are on a set of shelves that is covered most of the time with a mylar blanket to hold in the heat, as the room is kept at about 60 degrees. The seed trays are 65-70 degrees there. The seed was sprinkled on top of moist starting mix, and then sprayed into the soil a bit with a mister.

I'll try a few on my top shelf which is warmer (I have germinated Begonias successfully there) and try saturating the soil a bit more and see if that helps the germination rate.


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

Mandolls it's odd that your seed from this year didn't germinate when your seed from the previous year did.

You said your trays were sitting on top of the fluorescent lights? Do you mean the trays were on top to get bottom heat and received no light?

The temp was a little on the low side for germination and that could easily have contributed to rotting in a moist environment. Germinating temperatures of 75-80 would speed up the rate of germination by days giving the seed much less time to rot.


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

Having lived for forty years in the Pajaro Valley of California where hundreds of acres of lettuce is grown, three crops a year being the norm, I just don't see the point of picturing it as a difficult operation. If your post is helpful to others, and is not a cause for discouragement, that is fine with me. Al


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

"Mandolls it's odd that your seed from this year didn't germinate when your seed from the previous year did.
You said your trays were sitting on top of the fluorescent lights? Do you mean the trays were on top to get bottom heat and received no light?"

I have been testing different types of lettuce over the past three years to see what does well for me. I have had several types that seemed difficult to germinate, while others germinated really easily.

Seed that needs 65-75 degrees for germination I start on top of my fluorescent lamps for bottom heat. (in a room that is kept about 60 degrees) They get ambient light since I use the 2nd group of lamps from the top and there are 4 shelves of lights, but not direct light.

I start heat lovers on the very top shelf under lights where it is closer to 75-78. Until I read your post I had never seen anyone recommend that much heat and light for lettuce. I'll give it a try and see if it makes the difference.


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

Thanks! This is great info as I was just about to try starting lettuce indoors for the first time. Especially found the saran wrap/when to remove/when to mist vs saturate/when to dry out part very helpful. Thanks so much for posting your knowledge :)


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

Thank-you for this post! I'm surprised that someone would think germinating lettuce, or anything, frankly, would be so simple there needn't be detailed info online for how to do it. I appreciate the details. I'm a somewhat experienced gardener with many years of successful crops of many sorts, but have been struggling with my lettuce this spring. Your post helps.
My problem? I think it's my attempt to use up old seeds. They've worked superbly for things like kale, tomatoes, peppers, eggplant, etc., but lettuce is just not working. I have to go buy some new seed. This stuff is at least two or three years old. It worked last year with limited success; but this year, nothing. These ones have just been molding on me under my light set-up. Very frustrating. And even with experience we sometimes need a list to problem-solve. Thanks!


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

I have planted my whole life, and I'm still an amateur because I learn new things every day about it...and in fact, I often have to learn the same things over and over. I did not know lettuce seeds needed soaked either. One never knows it all...


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

Bumping this up to the top of the list (so I can find it again!).

Black Seeded Simpson has been easy for me. But that's where the magic ends. I may try germinating some other lettuce inside this season to see if I can do better. And I'll toss out my old seed while I'm at it. Thank you, soulreaver and others!


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

Like "Calistoga" said above, lettuce is one of the easiest plants to grow from seed. I have grown it all my life, and always have covered the seed with 1/8" to 1/4" of finely sifted soil, and it always germinates perfectly. I have never found that the seeds need light to germinate successfully.

Sorry to disagree on this item, but it does seem rather important. The instructions on the seed packets typically say to cover the seed also. The website below has an extensive section on growing lettuce from seed, and it also recommends covering the seed. Scroll down to the section on lettuce.

The advantages of covering are that it keeps the seeds moist for far longer, and this actually aids germination.

Here is a link that might be useful: French Intensive gardening method


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

I have a lettuce (outside) that sprouted and has sent roots
down an amazing 3 " but doesn't seem to grow. It's staying small. Is this a temperature thing? We've had a cold spring, mostly in the 50's.


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

Starting lettuce from seed has to be the easiest thing in the world to start. It's almost impossible to not get it to sprout. I am totally confused with this thread. KISS method works just fine. Just my opinion.

This post was edited by dirtguy50 on Fri, Apr 4, 14 at 22:11


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RE: Guide To Help Others Germinate Lettuce Seeds Successfully

I am puzzled as to why those that think this thread is pointless are even reading it posting here?

I appreciate this post. I am a fairly new gardener, in my third year of veggie gardening. I plant as much as I can in my limited space around my small, city backyard. To make it worth it, I need to get as much success as I can out of these small plantings, and therefore try my best to get it right the first time. I had great success last year with all of my crops, except for some reason, not with my leaf lettuce. This year, the seeds have sprouted and are under a florescent light, but the little seedlings have started laying down. They are just about a week old. As of now they are still green. Any thoughts on what is happening? Might I be over/under watering? Can I save them? Thanks in advance for your help!

This post was edited by lovelyother1 on Fri, May 2, 14 at 21:40


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