Lettuce is one of the most well-known salad greens. It’s easy and quick to grow, and it’s shallow root system makes it ideal for container gardens and big backyards alike.
Here's what you'll need to know to help your Lettuce thrive!
We created the below video and transcript to walk you through:
Glossary of Lettuce terms
Varieties of Lettuce available
Starting your Lettuce seeds
Caring for Lettuce at all stages
Fertilizer and/or Mulching
Transplanting best practices
Companion Plants do’s and don’ts
Common Problems and Their Solutions
Pests, Diseases and what to do about them
Harvesting and storing your Lettuce
TERMS TO KNOW WHEN GROWING LETTUCE
Before we get started, let’s learn a little bit about lettuce
TRUE LEAVES: The first leaves that look like those of a mature plant. These true leaves have a tougher cell structure and, depending on the variety, sharper edges compared to the soft seedling leaves.
BOLTING: The premature production of a flowering stem before it can be harvested. It’s the plant’s attempt to produce seeds for reproduction before it dies.
HARDENING-OFF: The process of gradually getting seedlings used to outside conditions like wind and sun before being transplanted. This is done by reducing the plant’s water intake and temperature and setting them outside a few hours each day for about a week before transplanting.
THINNING: Gently removing seedlings at a certain growth stage to leave only the strongest and most mature plants behind. This encourages proper plant growth and allows lettuce to thrive without any major competition.
OPEN POLLINATED: Plants, like lettuce, that either pollinate themselves or get pollinated by insects as they move from plant to plant.
Lettuce is typically divided up into a few main categories.
CRISPHEAD (SUMMERTIMES, SALINAS, ICEBERG)
Its thin and crisp leaves often have curled or serrated edges.
BUTTERHEAD (BUTTERCRUNCH, ESMERALDA)
This variety has loosely folded leaves that are green on the outer parts and cream or yellow on the inner ones. It bruises and tears easily so it needs careful handling.
ROMAINE (LENTISSIMA, ITALIAN BLONDE ROMAINE)
This lettuce variety grows upright. Its outer leaves are smooth and green, while the inner leaves are colored whitish to green.
LEAF (RED SAILS, OAKLEAF, SALAD BOWL)
Leafy varieties don’t form a head. Their leaves can be serrated or crinkled, and the colors vary from light green to red.
To germinate, lettuce’s ideal soil temperature should be between 50-75°F (10-24°C). Any temperatures that are above 80°F (26°C) can have a negative impact on the seeds’ germination process.
Lettuce seeds also need a little light to germinate, so make sure not to cover them too heavily with soil. You can sow them about a quarter to a half-inch (0.6-1.3cm) deep.
Once your plants have 3 -4 true leaves, you’ll want to thin them to be 8-12 inches (20-30cm) apart. The best part about thinning lettuce is that the plants you’ve thinned can actually be transplanted elsewhere in your garden, just as long as some of their roots are still intact!
Keep in mind that in your garden, both seeded and transplanted lettuce should be spaced 8-12 inches (20-30cm) apart in rows that are 18-36 inches (46-91cm) apart.
Harden-off your lettuce seedlings about 3 days before transplanting by reducing their water and setting them outside a few hours each day.
When properly hardened-off, lettuce plants can withstand temperatures as cold as 20°F (-6°C).
Transplants should have 4-6 true leaves before you set them outdoors - which usually takes about 5-6 weeks.
Place crisphead and romaine variety transplants 10-12 inches apart (25-30cm), in rows that are 18 inches (45cm) apart.
For other varieties, place them 8 inches (20cm) apart in rows that are 12-18 inches (30-45cm) apart.
THINKS TO KEEP IN MIND WHEN CARING FOR LETTUCE
Lettuce prefers sandy, well-draining soil with a pH between 6.0 – 7.0, and it won’t tolerate acid soils, so keep in mind that you may have to amend your soil first.
Lettuce needs full sun to thrive, but in hot weather, partial shade can be helpful. It grows best when air temperatures don’t go above 75°F (24°C), and lettuce can also tolerate temperatures down to 32°F (0°C).
Water stress causes lettuce plants to grow bitter, so make sure you water your lettuce regularly. Too much water stress, as well as high temperatures at night, can cause your lettuce to bolt.
Since lettuce is also shallow rooted, you’ll want to avoid disturbing their roots when working in the soil, like when you remove any weeds.
FERTILIZING AND/OR MULCHING
It’s beneficial to work some compost into your soil at least 3 weeks before planting your lettuce.
You can also work 4-6 cups of an all-purpose fertilizer for each 100 square feet (9m2) before you plant.
Side-dress with some nitrogen fertilizer (21-0-0) about 4 weeks after transplanting or thinning, and then water it into the soil.
Mulch with straw, grass clippings or wood chips to avoid water stress and to keep your soil cool as temperatures rise.
Mulch also controls the growth of weeds which can compete with your lettuce for water and nutrients.
GROWING STRUCTURE CONSIDERATIONS
They improve the drainage of your soil, which will also have a higher temperature than the ground. This helps prevent the spread of certain diseases that favor cool and/or moist conditions. Bonus, you can also avoid disturbing your plants while working on them, since you don’t have to step directly onto the soil!
They’re a great option if you’ve got limited space in your garden area. Make sure the pot is big enough to accommodate the roots, and also that it has holes in the bottom for water drainage. If your soil can’t drain properly, it can cause diseases like root rot to your plant.
First, check your soil for fertilizer needs and possible disease infections before planting. As well, with an open field, typically you won’t have to water as regularly as container-raised plants.
Anything from the Brassica family
Celery, Carrots, Cucumber, and Dill
Garlic (often repels aphids)
Onions, Radishes, Spinach, Squashes, Strawberries
COMMON CHALLENGES …AND SOLUTIONS
There are a few pests and diseases that can potentially harm your lettuce crop. Not to worry – we’ve listed them below, plus how to either avoid or fix the problem.
APHIDS: These green or black insects feed on the undersides of leaves, causing them to crinkle and curl.
Solution: In addition to companion planting, use insecticidal soaps or a strong water stream to wash them off.
SLUGS: Soft or hard-shelled pests that chew holes in the leaves. They’re mostly a problem with early or late lettuce plantings.
Solutions: If possible, hand-pick any slugs at night when they’re most active.
You can also try attracting them to “beer traps” beer. For this:
dig a hole in the ground and place a large cup or bowl into the hole. It’s best to use something with steep sides so that the slugs can’t crawl back out when they’re done like a mason jar.
Fill the jar about half full with beer, and let it sit overnight.
In the morning, the jar should then be full of drowned slugs that can then be flushed down the toilet.
Another option is placing a barrier around your plants of diatomaceous earth (a natural powder made up of the skeletons of tiny aquatic creatures).
FLEA BEETLES: Small black beetles that feed on seedlings. They may reduce plant stands or kill seedlings.
Solution: Practice good crop rotation, and remove any weeds around your growing area to minimize the amount of host plants for the beetles.
DOWNY MILDEW: A disease caused by low temperatures and long leaf wetness. It causes yellowing of the leaves in angular patches, while white lesions will also appear that later turn brown and papery. Downy mildew can reduce yields, and damage done by this disease can act as an entry point for more diseases.
Solution: Practice proper crop rotation. As well, reduce leaf wetness by planting your lettuce in its appropriate spacing, and also avoid using overhead irrigation. Control any weeds that may affect the air circulation between your plants, and make sure to also destroy crop residues after harvest.
MOSAIC VIRUS: A virus that’s typically spread by aphids, it causes leaf malformation, the yellowing of your plant, and it also stunts their growth.
Solution: Plant resistant varieties if they’re available. Using mineral oil can also be effective against aphid pests, who transmit the If you spot any plants with the mosaic virus, be sure to remove and destroy them.
LEAF SPOT: It usually starts on older leaves as small irregular spots. When those lesions grow, they turn brown and dry out. Severe infections can become an entry point for other rotting diseases.
Solution: Plant disease-free seeds and remove any infected plants. Also, avoid long leaf wetness by watering in the morning and reducing plant density. You’ll want to avoid working in your garden when plants are wet, since leaf spot is mainly spread by splashing As well, you’ll want to practice crop rotation.
ALSO GOOD TO KNOW:
TIP BURN: Caused by a calcium deficiency, the tips of the leaves will turn brown and collapse towards the ground. It can happen when your plants are growing too rapidly and can’t supply all the leaves with their needed nutrients
Solution: Avoid any excessive use of nitrogen-based fertilizers, and manage their moisture intake by watering them consistently
Crisphead variety: harvest this variety when the heads are firm.
Butterhead variety: harvest when the heads are in an early maturing stage.
Leaf varieties: this lettuce can be picked any time after the leaves have formed but should be picked before the seed stalk forms. Older leaves can be stripped off the plant to give younger ones more space to grow.
When harvesting your lettuce, either pick leaves or harvest their whole heads by cutting them at the soil level. You’ll want to harvest earlier rather than later, because the more mature the leaves grow, the more bitter they become.
We recommend harvesting in the morning, when your lettuce’s leaves will be crisp and full of moisture.
Lettuce can be stored for about 1-2 weeks in the fridge, either wrapped in moist paper towels or in plastic bags.