How to Plant Lettuce for Salads This Fall
People want to know where their food comes from, and there is no shorter answer to that question than a bed in your own backyard. Lettuce is a good place to start, because it is fast, it is forgiving, and you can cut from the same plant for weeks.
Lettuce is a cool season crop, so the best time to plant in Nashville would be early fall (Late August - Early October) or spring (March - mid-April) . You can sow straight into the ground through or start seed inside in late August and transplant. Either way, you could be cutting salad in about a month, since lettuce matures in about 30 days to baby leaves and closer to 60 for full heads.
What I love about starting from seed is that you get access to plants you will never find at a store or a nursery, including varieties from other countries. I like trying new things, so when I have the choice between seed and a transplant, I take the seed.
What you need
Lettuce seed. Leaf and romaine types, not iceberg.
Seed starting mix, which is a soilless mix and not garden soil.
A seed starting tray, standard 10 by 20 inch.
A second solid tray with no drainage holes, for bottom watering.
A grow light
A soil thermometer. Typical cost is about ten dollars, and you can use it season over season.
Compost for the bed or container you are transplanting into.
An eight-quart bag of soilless mix fills about two standard trays. If you are in Nashville, I get mine at Bates Nursery & Garden Center.
How long it takes
Starting a tray takes about twenty minutes, plus a few minutes of daily upkeep over the next three weeks and an afternoon to transplant. Direct sowing takes about the same amount of time up front, but skips the transplanting step entirely. You can expect your first harvest roughly 30 to 60 days after planting depending on whether you harvest baby leaves or wait for full heads of lettuce to mature.
The steps
1. Pick your lettuce, and skip the iceberg
Head or iceberg lettuce is what most of us know from the grocery shelf, but it is not the best choice for a home garden. It takes longer to grow, it is fussier, and you only get one harvest out of it once the head is fully formed. Leaf lettuces and romaine give you weeks of picking off the same plant.
This year, I ordered from Johnny's Selected Seeds, which has a good selection of organic seeds and consistent quality. I am planting: Encore Lettuce Mix, which is green and red oakleaf, green and red romaine, red leaf and bibb all in one packet; Jericho romaine; and a packet of organic salad arugula. They all mature fast.
2. Check your soil temperature before you decide where to sow
This is the step that decides everything else, and almost nobody does it. Lettuce seed is particular about temperature. A soil thermometer costs about ten dollars and removes the guess work. Measure at about 2 inches for direct sowing and about 4 inches for transplants.
Here is what the numbers mean:
40 to 80 degrees is the working range. Seed will come up anywhere in this range.
Around 75 degrees is the sweet spot, and seeds sown in this range usually sprout in two or three days.
At 50 degrees seeds will still germinate but it may take up to a week.
Above 80 germination is unreliable, and above 95, seeds may not grow at all.
In late August, the temperature of the soil in a raised bed in Nashville that gets full sun is typically somewhere in the eighties. This is why many people who plant seed out too early may see their fall lettuce seeds fail even when spring lettuce crops successfully sprouted in the same spot. It is not you and it is not the seed.
So the rule is simple - If your soil reads below 80°, you can sow straight into the ground or your garden bed. If the soil temperature is hotter than that, start your seed indoors where you can control the temperature, and transplant in a few weeks when the ground has cooled.
3. If you are starting inside, set up somewhere you will remember to check
Steps 3 through 7 are for indoor seed starting. If you sowed straight into the ground, skip ahead to step 8.
Pick a spot with room for the tray to sit undisturbed, near an outlet for the grow light, and ideally close to where you fill water. If it is out of the way, it can be easy to forget about your seeds and seedlings.
4. Sow the seed
Fill the tray with damp soilless mix, sow seeds at the depth indicated on the packet, and label everything. Lettuce seed is small and shallow, so a light covering of soil is all it wants. Planting too deep is one of the most common reasons seedlings never come up.
I put two seeds in each cell. If both come up, I pull one out once they start growing. This is a process called thinning. One seed per cell works just as well, and it is the better choice if you are trying to save seed or watching what you spend.
And remember, it’s normal and expected that some seeds might not sprout. So, don’t be hard on yourself. That happens to everyone.
5. Water from the bottom
Most of us are used to watering from above, but a stream of water can flatten a young seedling or wash away small seeds. Set your seed tray inside a solid tray with no drainage holes, pour water into the bottom, and let it soak in p through the drainage holes. It is gentler and it helps pull the roots downward.
Do not judge by the surface. Grow lights dry the top of the mix and make soil look thirstier than it is. The soil should feel like a damp sponge. Poke a finger into the side of a cell, away from the seedling, and check how dry your soil mix actually is before watering. If it feels dry about an inch below the surface, you should water.
6. Harden them off over a week
When your seedlings are two to three inches tall and have two to three sets of leaves, start getting them used to being outside. Put them out for an hour the first day, then add about an hour a day for a week, bringing them back indoors between. Start on an overcast day if you can, because full sun on a seedling that has only known a grow light can damage or burn the leaves..
7. Plant them outside
While they are hardening off, get your garden bed ready. Mix in compost and dampen the soil before you plant. Lettuce wants good drainage and soil that is not crusted or compacted.
Plant seedlings with about six to twelve inches between each plant depending on the variety. You can plant closer together if you plan to harvest often, which works well for leaf lettuce types. Handle your plants gently, they are still fragile. Set the root ball level with the soil line so the stem is not buried, then water at the base of each one to close any air pockets around the roots.
8. Sow again in two weeks, and again after that
This is the step many people skip and then wonder why they only had salad for ten days. Sow a new tray (or what you can fit in your bed/container) every two to three weeks and you get a continuous supply instead of one large harvest that is ready all at once. It only takes you twenty minutes each time.
9. Harvest early and harvest often
At the store you buy a whole head, which is why many people wait until that growth stage to harvest their lettuce, but you don’t have to. You can begin cutting leaves as baby greens without cutting down the whole plant. Harvesting this way, one plant will feed you for weeks.
Pick in the early morning when the leaves are crisp and holding the most water. For leaf lettuce, start when the leaves are four to six inches, and take the older outer leaves first. Use clean scissors or snips and cut close to the base. Leave the small center leaves alone so the plant keeps producing. As a rule for anything leafy, never take more than a third of the plant at once.
I clean my snips in a mixture of peroxide and water after every use so I am not moving potential disease from one plant to the next.
If you are growing in Nashville
We are zone 7b, and our average first fall frost is 25 October. Count backward from there and you can see why the sowing window closes when it does. Lettuce needs 30 to 60 days depending on whether you are cutting leaves or waiting for heads, so seed that goes in around the middle of September will allow you enough time to get a fall harvest.
Lettuce is happiest around 50 degrees at night and 60 to 70 during the day. Above 85 the quality drops off and the plant will bolt, which means it starts to flower and the leaves turn bitter. You can find the frost dates for wherever you are at almanac.com.
Questions people ask
When is the best time to plant lettuce in Nashville?
Early spring, March through mid-April, and early fall, late August through September. Lettuce needs cool temperatures to grow well. If you are in a different climate zone, the timing shifts whenever your season turns mild, but the principle is the same.
What if I just want to sow straight into the ground?
Go ahead, especially if your bed is already prepared and your soil is reading under 80 degrees. Starting inside gives you control over conditions while the plant is small and fragile, but direct sowing works well too with the right conditions and care.
What does cool season crop actually mean?
It means the plant does its best growing in mild weather rather than heat. Lettuce, spinach, arugula, kale and radishes are all cool season. Tomatoes, peppers and squash are warm season plants.
My seeds never come up. What am I doing wrong?
Usually one of four things. The seed is past its use date and no longer viable, or the seed is planted too deep - The seed packet will give directions on depth to plant. The soil is too warm or too cool. You are watering too much or too little. Or the light is too far away, which shows up as long stretched seedlings that fall over because there is no structure holding them up.
Where to go from here
If you are starting from scratch this season, grab our free Garden Starter Guide.
Susanna Hadley is the founder of THE SEED LOCAL, a Nashville gardening community built on the idea that you do not need to know everything to grow something. She designs and plants gardens for a living, and she is still learning something every season, which is most of what she writes about here.
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