There’s no demand shortage for fresh lettuce from spring through the first hard frost of the year. If you’re growing in a warmer climate with no frost, you can grow it all year long. While you can purchase seedlings, growing lettuce from seed is inexpensive, easy, and allows you to try types not easily found at the store.
With countless varieties to choose from with different needs for growing conditions, there is something for everyone. Starting lettuce from seed can be easy, fun, and rewarding. Let’s get started.
Lactuca Sativa Overview
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Why Transplant Lettuce?
Being able to control the environment of your seeds can help yield a better crop.
Can you direct seed lettuce into your garden? Sure you can. But here are a few reasons why starting indoors from seed is recommended.
- Saves you space in your garden. Not every seed will germinate, and when they don’t, you’re left with wasted space in your garden.
- Survival of the fittest. You can select the best-looking, healthiest seedlings to transplant into your garden. Leave the other guys behind.
- You get a head start. You can start seeds indoors while the weather outside is still not ideal for gardening. When the soil can be worked, and you’re ready to garden, you’ll be a few weeks ahead of schedule with your seedlings.
Choose the Right Variety
There will be varieties that will thrive better than others, depending on which zone you live in.
Lettuces have been bred to perform in all types of weather conditions and growing regions, offering some for the early season when daytime temperatures are still low, peak summer when the sun is hot, and even some that do best in cooler fall weather when frost is possible. Check out these heat-tolerant varieties if you want to grow lettuce in a warm region.
Things to consider when choosing varieties:
- Growing region
- Sun exposure needs
- Soil requirements
- Fertility needs
- Space needed
- Amount of space you have available
- Days to maturity?
Romaine Types
Romaine lettuce is one of the most popular lettuce varieties to grow among gardeners.
This is by far the most popular type in America. It’s crisp and flavorful, and no Caesar salad is complete without it. It grows tall and compact, with thick ribs and a sturdy “heart” inside. It’s pretty tolerant of heat, unlike some other lettuces.
Romaine has a well-balanced combination of folic acid, potassium, vitamin C, and beta-carotene. Try ‘Little Gem,’ which is sweet like butterhead lettuce with all the benefits of romaine.
Oakleaf Types
The oakleaf variety is known for its nutty flavor.
Oakleaf lettuces have deeply lobed leaves resembling those of an oak tree. There are both green and red varieties. They can be harvested as full heads or individual leaves. Some say it has a slightly nutty flavor.
Looseleaf Types
This lettuce is crisp and has a mild flavor.
Looseleaf lettuces have loose open heads with frilly or curly leaves. They won’t form a full compact head and are typically quite crisp and mild in flavor. This type is great if you just need to grab 1-2 leaves for burger night and is a favorite among chefs due to the fancy nature of the curled leaves. Try ‘Black Seeded Simpson’, a frilly lettuce with heat and drought tolerance.
Butterhead Types
Butterhead lettuce is a popular choice for wraps and sandwiches.
Named for its buttery smooth texture, butterhead lettuce is usually grown to a full head. These varieties offer a mildly sweet flavor and tend to hold up quite well for wraps and sandwiches.
Summer Crisp (Batavia) Types
Summer crisp varieties have a sweet, juicy flavor.
These are typically pretty heat-tolerant and slow to bolt, making them a great option for warm region growers. They offer sweet and juicy flavor without bitterness. Batavia lettuce can start off looking like a looseleaf variety but will head out and become more compact.
Lettuce Mixes (Mesclun)
The wonderful thing about mixes is that they can be harvested at different times.
Mixes can be harvested anywhere from 3-6 weeks as baby greens or full-sized leaves. Each variety in a mix is selected for its texture, flavor, and appearance, and they should all mature around the same time so one variety does not become shaded out by the others.
Sow a new patch every few weeks for a continuous supply all season. Try ‘Farmer’s Market Blend’ Mesclun lettuce for an easy-to-grow mix of flavorful lettuces in different colors and textures.
Supplies You’ll Need:
Make sure to be prepared with all the supplies you will need before you start sowing your seeds.
Before getting started, gather all your supplies.
- Seeds
- Cell trays
- Seed-starting mix
- Dibling tool (optional)
- Propagation domes (optional)
- Water
- Heat mats (optional)
- Access to direct sunlight or a supplemental light source
- Tags or labels to indicate the variety
Propagation
Lettuce seeds should germinate within 7-10 days or sooner when heat is applied.
Fill your containers or cell trays with seed-starting mix and tamp it down by dropping it gently a few times on the work surface. This ensures there aren’t any air gaps in the cells that will inhibit proper germination. Germination requires good seed-to-soil contact. Fill the trays up almost to the top. Then, using your pinky finger, a dibbling tool, or the end of a pencil, make a small indentation in the center of each cell. Aim for 1/4″ to 1/2″ deep, but no deeper than 1/2″.
Drop a seed into each indentation, placing it horizontally along the soil surface and ensuring it’s flat. Then, cover them up with more seed-starting soil and gently tamp down your tray again. Using a mister, spray the tray until it’s evenly moist.
Put the tray onto a heat mat if you’re using one, and set it to 68°. Check water more frequently if using a heat mat, as they may dry out faster. If not, place the tray in a mild area or cover it with a propagation dome to hold in some humidity.
Lettuce should germinate in 7-10 days, sometimes sooner with a heat mat. When you see germination, set the tray under a grow light or in sunlight.
Caring For New Seedlings
Seedlings won’t survive if they get too dry or dry out completely.
Check the water every day so your seedlings don’t dry out. Give them a nice, even misting so the soil is moist but not soggy.
If you notice your seedlings are becoming skinny and tall, your light source is not strong enough, or they are too far from it. This is what’s called “leggy,” and you should adjust the lighting right away.
Lettuce can return from this, but legginess may affect their initial growth stage. Whereas some other crops can be buried deeply when transplanted and roots take over, lettuce does not have adventitious roots, so you cannot bury the stem, even if they’re leggy.
Hardening Off Seedlings
Don’t skip hardening off your seedlings.
Hardening off before transplanting is a very crucial step that is often missed, and the results of not completing it can be devastating.
What is Hardening Off?
Hardening off your seedlings helps them acclimate to your specific climate and weather conditions.
Hardening off is incrementally changing the environment from inside to outside before transplanting your seedlings into the ground. This allows them to slowly acclimate to the outside happenings, such as rain vs. your gentle watering schedule, wind gusts, harsh sun, pests, etc. If seedlings are not properly hardened off, they will likely be in shock, leading to stunted growth, poor performance, or death.
How to Harden Off Seedlings?
Choose a day with a little cloud cover when it’s time to place your seedlings outside.
Hardening off should start by taking seedlings from inside your home, greenhouse, or wherever they were propagated and move them to a shady area outside. Do this for just a half day, ideally on a cloudy, mild day. Then, bring them back inside for the night. Do this a few times while decreasing their water so they start to fend for themselves.
After a few days of this, leave them outside overnight. If you do this in the spring, you may protect them the first few nights with row cover. Eventually, you can leave them outside overnight with no coverings. This process should take about a week. Then, your seedlings are ready to be transplanted into the ground.
Preparing Garden Beds
Adding hoops can help to provide shade by supporting tarps or shade cloth.
Lettuce prefers loose soil that’s well-draining. Work well-aged compost into the top few inches before transplanting. If you plan to hoop your garden bed for insect netting or shade cloth, gather these supplies or go ahead and stake out your hoops. You can also lay drip irrigation lines at this time or lay them in a nearby path until after you’ve transplanted.
Try planting lettuce in one of Epic Gardening’s metal garden beds. They’ll allow the soil to drain and keep the soil structure nice and open, have no compaction from footsteps, and might even help ward off some pests and diseases present in the ground soil.
Transplanting
It’s time to transplant when your seedlings’ roots are white and abundant.
Lettuce can be transplanted about four weeks after seeds are sown. They should have 3-4 true leaves and be about 2-3 inches tall. Roots should be white, abundant, and strong. If you keep the seedlings in the cell trays too long, they’ll become rootbound and stressed, so be sure to get them out before that happens.
Using a knife or by gently squeezing the bottom of the cell, remove each seedling. If you’re using the Epic cell trays, use your fingertip to pop the seedling up from the bottom easily. Ensure you get all the contents out so you don’t remove any of the roots. Use a trowel to open up a hole about the same size as the seedling so as not to bury the stem. Tuck one seedling into each hole and surround it with soil, tamping it down. Water your transplants immediately after transplanting. Cover with insect netting or shade cloth at this time if you’re doing so.
Pro tip: Add a mycorrhizal inoculant to each transplant hole to help the lettuce establish a strong root system.
Spacing
Proper spacing will give your lettuce the best yield.
Lettuce should be given at least 6 inches of space to themselves. Small types, like ‘Little Gem Mini-Romaine,’ ask for just six inches, while larger varieties, like ‘New Red Fire,’ should be given 12 inches.
Some growers successfully plant lettuce in the shape of a “5” on a die. Space out two lettuce heads on the outside rows, then add another in the center row where the center dot of the “5” would be.
Watering
A drip system is the best way to keep your lettuce watered and healthy.
Lettuce is made up of about 94% water, which means it needs a lot of it to grow well. First and foremost, lettuce needs a lot of water while growing because its roots are shallow and can dry out easily if it’s not receiving enough water. The soil should always be moist 1-2 inches below the soil surface.
Depending on estimated rainfall, plan to water your lettuce several times a week or more in hot growing climates or hot, sunny weather stretches. Drip irrigation works best for lettuce as it will get water straight to the shallow roots and steadily flow to keep the soil moist.
Pro tip: Group crops together in your garden with similar watering needs.
Sun Requirements
Some lettuce varieties can tolerate more sun than others.
Most lettuce prefers to be in full sun, receiving 6-8 hours of sun a day, but some varieties can tolerate partial shade, receiving 4-6 hours of sun a day.
Succession Planting
Sowing and transplanting seeds every 2-3 weeks will give you a steady flow of lettuce.
If you’re growing head lettuce and want a steady supply all season long, plan on sowing seeds every 2-3 weeks. This method is called succession planting. If you’re transplanting every few weeks, you should have no shortage of lettuce.
Be sure to pay close attention to the ‘days to maturity’ on the seed packet and consider the time of year, as some lettuces will grow a bit slower in the spring and fall.
Fertilizing
Your lettuce will need a nitrogen fertilizer every four weeks to help promote growth.
Lettuce needs well-balanced and fertile soil, so keeping your soil healthy is important to growing healthy lettuce. Following the guidelines of your soil tests, you should amend your garden beds before each season so it’s as close to balanced as possible.
Lettuce will benefit from a high nitrogen fertilizer applied about four weeks after transplant to promote growth and a liquid fertilizer every few weeks thereafter. Remember, if you’re interplanting with a heavy feeder like tomatoes, the feed should be more advanced to ensure both crops have what they need.
Harvesting
Different lettuce varieties will require different harvesting methods.
The type of lettuce you’re growing will determine how and when you harvest. You should mark down the first potential harvest date for each variety based on their estimated days to maturity. Then, head out to your garden and check on them.
Full heads should be firm and sturdy. Grab them with one hand and give them a jiggle. If the leaves are still flopping around, it needs more time to firm up. If the base is nice and strong and the leaves stay together, it’s time to harvest. This method works for looseleaf varieties as well.
Romaine lettuces grow straight up and should have all their leaves folded in on themselves tightly, giving it a rounded appearance at the top. Lettuce mixes can be harvested beginning at the three-week mark as baby leaves.
Cut and Come Again Method
Harvesting just the leaves will allow your lettuce to continue to grow.
With many lettuces, you can preserve the lettuce crown by harvesting the oldest leaves from the outside, allowing the inner leaves to continue growing. This will allow you to come back again and again for a few leaves at a time and is called the cut and come again method.
Dealing With Pests
There are a few different methods for dealing with pests in your garden.
Certain pests can quickly decimate a whole lettuce crop if an infestation is bad enough. Let’s review a few heavy hitters and what you can do about them going after your lettuce.
Aphids
Ladybugs are known to feed on aphids but will need enough food to eat to stick around.
If you’ve ever seen tiny little green, yellow, or white bugs on your lettuce leaves, they’re probably aphids. They are sap-suckers, sucking the juice and life out of your greens, including lettuce.
Ladybugs and lacewings love to feed on aphids, so try attracting those to your garden with dill, daisies, oregano, cosmos, sweet alyssum, and asters. You can also order some of these for release. Just be sure there is enough food for them, or they will just fly off.
Slugs
These mollusks can wipe out a lettuce crop pretty quickly.
Slugs love to hide from the sun inside lettuce heads, and while they’re there, they will eat to their heart’s content. You’ll know slugs are present if you see a slime trail nearby from the night before.
Slugs are attracted to yeasty beers, so pour some in a shallow pan and set it into the soil, ensuring the lip of the pan is flush with the soil surface. They’ll eventually drown in the beer and no longer be a bother. Alternatively, you can sprinkle an organic snail bait around the base of your plants. Organic snail baits such as Sluggo® have an active ingredient of iron phosphate, which will kill slugs within several days and then break down into soil fertilizer. Some also contain a very small quantity of spinosad, a soil bacteria that also works to kill off pests.
A copper wire perimeter might also work. When the mucus of a slug comes into contact with copper, it creates a current and zaps the slugs, which may deter them from entering the area again. However, copper wire is less reliable than using a bait like Sluggo.
Caterpillars
Cover crops with netting to prevent caterpillars and other larvae, as well as moths that lay eggs on plants.
Caterpillars include cutworms, armyworms, and cabbage loopers; they’re all horrible news for your lettuce. Covering new transplants with insect netting decreases the eggs laid on your crops and results in less damage. Since lettuce doesn’t need pollinating, there’s no reason to remove the netting until harvest.
Beneficial insects like parasitic wasps should keep caterpillar populations down. Buy these beneficial insects, or attract them to your garden by planting sweet alyssum, common dill, coriander, tansy, marigolds, and cosmos.
Preventatively, you can spray the insecticide Bacillus thuringiensis. When ingested, caterpillars will die.
Flea Beetles
Herbs such as sage and mint may help deter flea beetles from invading your lettuce.
Flea beetles overwinter in brush and emerge just about the time you might be transplanting lettuce. They cause cosmetic damage by chewing little holes in greens, making them appear lacy. In young transplants, their damage can be catastrophic. The more serious concern is that flea beetles can carry pathogens that cause bacterial wilt and blight.
Insect netting and row cover can effectively keep out most lettuce pests. Flea beetles don’t like strongly scented herbs like sage, mint, and hyssop. You can also plant a trap crop, such as marigolds or radishes, to deter them from your lettuce.
Dealing With Diseases
A few common diseases can be spread via pest transmission.
Aphids, flea beetles, and other voracious pests spread disease from plant to plant and crop to crop. Diseases can also come from infected seeds. Here are a few common lettuce diseases you might encounter.
Downy Mildew
This mildew is common in warm, humid climates.
Downy mildew (DM) is a water mold organism and has, unfortunately, developed some resistance to fungicidal treatments. It lives in the soil and is spread by spores. Symptoms will appear first on the underside of the leaves, where colonies first attack. If left untreated, the opposite side will mirror the whitish-bluish spotting.
If you’re growing lettuce in a warm and humid area, you have likely experienced this disease. Neem oil can help with the spread of DM if detected early. Neem oil won’t kill it if it’s already in the stems. A copper fungicide can also be sprayed every 7-10 days until DM is under control.
Prevention is key when it comes to downy mildew. Here are a few things you can do to keep this disease at bay:
- Keep your garden clear of debris
- Maintain good airflow
- Weed control
- Choose disease-resistant cultivars when available
Lettuce Mosaic Virus
Mosaic viruses are viral pathogens spread by infected seeds, aphids, or other sap-sucking insects.
Lettuce mosaic virus (LMV) can be seed-borne and transmitted to your garden via infected seeds but may also be spread by aphids and other insects that pierce the leaves to suck sap out. If lettuce is affected when it’s young, it may not form a head, may be disfigured, and can develop a mottled, yellow appearance.
How to avoid LMV:
- Sow resistant cultivars
- Practice good flea beetle management
- Remove garden debris, especially old lettuce crops
- Remove potential weed hosts
- Offer your garden a lettuce-free period to break the cycle
Lettuce Drop
Wilt and root decay may be a sign of lettuce drop.
Lettuce drop is caused by fungal pathogens that dwell in the soil and can be spread via wind. Both Sclerotinia sclerotiorum and Sclerotinia minor prefer cool, wet conditions when the soil is wet.
Lettuce drop causes wilt and decay in all parts of lettuce, causing it to collapse eventually and the crown to cave in. Sclerotinia minor will only affect the leaves in contact with the soil, whereas Sclerotinia sclerotiorum, in addition to lower leaves, affects upper leaves as well.
Cultural practices include:
- Raised beds for proper water drainage
- Crop rotation
- Removing infected plants
- Avoid overwatering
Since the pathogen is transported by wind, cultural practices are ineffective. Lettuce drop also has many potential hosts, including fennel, beans, cauliflower, radicchio, tomatoes, and even cover crops like vetch, mustard, and phacelia. Iprodione, boscalid, and dicloran are fungicidal treatments available, but there currently are no organic fungicidal alternatives. Currently, no cultivars show any significant resistance to lettuce drop on the market.
Corky Root Rot
This bacterial disease can destroy the entire crop, so prevention is key.
Corky root rot is caused by the bacterium Rhizomonas suberifaciens, which is soilborne and most prevalent in coastal areas where temperatures are warmer. Symptoms include yellow banding along the top of the taproot and lateral roots of young transplants. Wilting may occur in warm temperatures.
These bands will grow, turning green and rough, cutting off the plant’s ability to uptake food and water. Growth will generally be uneven, slow, or stunted, and yields will suffer.
How to prevent and treat corky root rot:
- Plant disease-resistant cultivars, when available
- Rotate crops
- Monitor nitrogen levels in the soil
- Biofungicides
Dealing With Weeds
It’s important to remove any weeds as they pop up, especially in the early stages of growth.
Weeds will easily outcompete lettuce, so create a weed-free garden bed before transplanting your seedlings. Allow the seedlings some time to get settled in, then gently cultivate between the lettuce with a wire weeder to eliminate any tiny newly germinated weeds. A few weeks after that, cultivate again. Once the heads start filling out, they should shade out any new weed seeds.
Pro tip: Play around with your spacing. The more bare soil between your lettuce, the more space for weeds to pop up.
Lettuce Companion Plants
Certain companion plants can help eliminate pests and diseases from popping up in your lettuce crops.
Many plants grow well with lettuce. It is pretty easy to pop in alongside tomatoes and beets. Calendula may help ward off slugs. Lettuce and alliums are a dynamic duo, as the fragrance of the alliums may deter caterpillars who want to munch on the leaves. And trellised cucumbers allow space for lettuce along the outside of the bed.
How to Keep Lettuce From Becoming Bitter
When you see bolting in your lettuce, it’s usually a sign of heat stress.
Lettuce can become bitter under stress, usually caused by extreme heat. Since lettuce is a cool-season crop, it will grow more quickly in the summer as it’s trying to go to seed, also known as “bolting.” Bolting will cause the innards of the lettuce to become hard and send a shoot up. Eventually, it will flower and drop seeds if left to its own devices.
If you’re growing in a warm region, try covering your lettuce with a 30% shade cloth. This will be especially helpful if you don’t have anywhere partially shady in your garden to plant lettuce. This will allow 70% of the sun to shine through while allowing good airflow and rainfall to penetrate. Plus, it keeps rodents and large critters like deer away.
Best Uses For Lettuce
Lettuce is a healthy addition to many popular dishes.
We all know no burger is complete without a crunchy piece of lettuce, but have you ever tried adding it to a smoothie for added hydration? Lettuces can also be used as a garnish on a charcuterie board or sushi platter, and sturdier types can even be grilled.
For anyone trying to limit their gluten intake, use a butterhead leaf as a wrap or base for an open-faced “sandwich.”
Health Benefits
Lettuce is loaded with important vitamins and nutrients.
Lettuce is naturally low in sodium and packs a punch of minerals like calcium, phosphorous, magnesium, and potassium. It’s also high in beta-carotene, which is important in the body because once converted to vitamin A, it helps keep skin, eyes, and bones healthy. Romaine, specifically, is high in vitamins C and K and folate.
The ancient Romans, Greeks, and Egyptians believed the milky substance in lettuce caused sleepiness, and it was used as an after-meal sedative. The milky substance contains the chemical compounds lactucopicrin and lactucin, which are believed to have pain-relieving and sedative effects. However, studies have only been done in lab mice, so only time will tell how much truth this theory holds.
Frequently Asked Questions
In cooler growing regions, start seeds 3-4 weeks before your last estimated spring frost. In warmer climates, start seeds in the summer for a fall harvest, and in early fall for a late fall/early winter harvest.
Keep washed lettuce wrapped in plastic in the crisper drawer between 32-36°. A paper towel or small dish towel inside the plastic bag will help absorb any excess moisture. Lettuce should keep this way for 7-10 days, sometimes longer.
Final Thoughts
There’s just nothing like fresh lettuce, and growing your own can be fun. Experiment with different varieties and spacing to see what works in your space. Take note of the results, including the different flavors!
If you’ve never started lettuce from seed, I hope you feel confident enough to try it!
