Like most other cool-weather crops, lettuce can be grown in the spring and fall. A great way to get a head start on the growing season is to start lettuce seeds indoors and move the seedlings outside. But when is the best time to move those lettuce seedlings into the garden? This full guide will show you when and how to move lettuce seedlings so that you have a successful crop.
How Long Should Lettuce Seedlings Grow Before Transplanting?
Lettuce seedlings typically need 4-6 weeks of growth after germination before they are ready to be transplanted outside. The seedlings should have at least 2 sets of true leaves and be 2-3 inches tall before transplanting. Trying to transplant the seedlings too early can shock them and stunt their growth.
Head lettuce varieties tend to grow a little faster than leaf lettuce varieties. But for any type of lettuce, size and leaf development, not age, are the best ways to tell if it’s ready to be transplanted. Instead of weeks after germination, look at the height and number of true leaves.
Ideal Size for Transplanting Lettuce
- At least 2 sets of true leaves
- 2-3 inches tall
- Well-developed root system
Before you move the lettuce seedlings, you want their roots to be well established. This gives them the best chance of quickly starting to grow again after being moved to the garden. Overgrown lettuce seedlings that are too leggy may need to be planted a little deeper to get their roots back to where they were.
When to Start Lettuce Seeds Indoors
Lettuce seedlings grow slowly at first, so start seeds indoors 4-8 weeks before your last expected frost date This gives time for the seeds to germinate and the seedlings to grow big enough to transplant on schedule
Stagger planting lettuce seeds every 2 weeks for a continuous harvest. The timing will depend on your climate:
- In warmer climates, start seeds 6-8 weeks before last frost
- In cooler climates, start seeds 4-6 weeks before last frost
The Earliest Time to Transplant Lettuce Outside
You can move lettuce seedlings outside up to three to four weeks before the last frost date in your area. Light frosts don’t hurt lettuce, but moving plants before this date increases the chance of cold damage.
Some gardeners wait until after the last frost to transplant lettuce as an extra safety margin. But transplanting a few weeks beforehand works well if you harden off the seedlings properly and protect them as needed.
Hardening Off Lettuce Seedlings
Hardening off is the process of gradually acclimating seedlings to outdoor conditions before transplanting. This toughens up the tender plants and helps them withstand transplant shock.
To harden off lettuce seedlings:
- Start 7-10 days before transplanting
- Move seedlings outdoors for just 1-2 hours on the first day
- Slowly increase outdoor time over the course of a week
- Bring seedlings back inside at night
- Leave seedlings outside overnight for the last 2-3 days
How to Transplant Lettuce Seedlings Outside
On transplant day, thoroughly water lettuce seedlings to make removal easier. Carefully dig up each seedling with roots intact. Prepare garden beds by amending soil and creating planting holes. Place each lettuce seedling into its hole, backfill with soil, firm gently, and water well.
Key transplanting tips:
- Handle seedlings by leaves, not stems
- Transplant on a cloudy day or late afternoon
- Water transplants regularly the first week
- Provide shade if hot & sunny after transplanting
- Watch for pests like slugs and cutworms
Lettuce Transplant Spacing
Proper spacing of lettuce plants prevents overcrowding and allows good air circulation. Distance between plants depends on variety:
- Head lettuce – 10-12 inches apart
- Looseleaf lettuce – 4-6 inches apart
- Baby lettuce – 2-3 inches apart
For rows of lettuce, allow 12-18 inches between rows. You can always harvest every other lettuce plant early as “baby” lettuce to thin out the spacing.
Growing Lettuce Transplants Under Lights
Growing lettuce seedlings indoors under LED grow lights allows you to control conditions for optimal growth. Use a seed starting mix in trays or pots. Lightly cover lettuce seeds and keep moist.
Once sprouted, move to 2-3 inches below the lights. Maintain temperatures of 60-70°F and humidity around 70%. Grow lights should be on 16-18 hours per day. Fertilize lightly with diluted liquid fertilizer once true leaves form.
Protecting Lettuce Seedlings Outside
Young lettuce transplants need some special care once moved to the garden:
- Add floating row cover to protect from cold winds
- Use cloches, cold frames, or mini-tunnels if cold overnight
- Provide shade cloth if temperatures exceed 75°F
- Mist leaves daily for the first week after transplanting
- Be diligent about weeds, pests, and diseases
With proper care, lettuce transplants will establish quickly and start growing fast. You’ll be harvesting homegrown lettuce before you know it!
Common Problems When Transplanting Lettuce
Lettuce seedlings are prone to bolting, tipburn, and rotting if conditions after transplanting aren’t right. Here are some troubleshooting tips:
Bolting – Premature flowering. Caused by overmaturity, heat stress, or transplant shock. Start new seeds every 2-3 weeks to stagger harvest.
Tipburn – Browning leaf margins. Usually caused by inconsistent watering. Water thoroughly and evenly.
Damping off – Seedling collapse from fungal disease. Avoid overwatering and increase airflow.
Leggy growth – Spindly, weak seedlings from insufficient light. Use grow lights or start new seeds.
Slow growth – Stunted plants fail to grow after transplant. Harden off better or wait to transplant larger seedlings.
With careful timing, preparation, and aftercare, you can avoid most issues and have great success growing lettuce from seed to harvest. Just remember not to rush – patience is key when it comes to lettuce!
HOW TO PLANT AND TRANSPLANT LETTUCE
Lettuce is one of the few vegetables that tolerates a bit of shade. A planting site with full sun and late-afternoon shade is ideal — especially as summer nears. Well-drained soil with rich organic matter provides the perfect foundation for all lettuce types. Before you plant, mix organic compost and a balanced fertilizer such as Pennington Rejuvenate Plant Food All-Purpose 4-4-4 into your soil. Lettuce grows best when soil pH is between 6.0 and 7.0, the range where most plants thrive.
Lettuce transplants are garden-ready when theyre three to four weeks old. Gradually acclimate transplants to the outdoors before you plant. Plant lettuce heads like romaine, iceberg, and butterhead 10 to 12 inches apart, 15 to 18 inches apart in rows. If youre planting in pots or in mixed gardens, allow similar space. For leaf lettuces, sow seed into garden soil. Plant four to six lettuce seeds per inch, in rows at least 2 inches apart. Many gardeners plant swaths of lettuces a foot wide — just keep widths manageable for harvesting. Lightly cover lettuce seeds with 1/8 inch of soil and press gently to ensure good seed-to-soil contact. Depending on the variety, most lettuces mature between 30 and 60 days after planting. Your seed packet will specify whats normal for the lettuces you choose. Plant fall lettuce four to eight weeks before your areas first expected fall frost. For near-continuous spring and fall lettuce crops, plant seeds in succession plantings every two to three weeks.
Head-forming lettuces take longer for harvest than loose-leaf types.
How to Transplant Lettuce Seedlings for HUGE Results
FAQ
Should you transplant lettuce seedlings?
There are 2 main ways to plant lettuce: 1) transplanting seedlings and 2) direct seeding. I do both, depending on my lettuce goals. If I want full-sized heads I prefer to transplant 4 week old seedlings. For baby greens I direct seed.
What cannot be planted next to lettuce?
It’s best not to grow lettuce next to broccoli, brussels sprouts, cabbage, cauliflower, kale, or kohlrabi. Some types of lettuce may help these plants, but not all of them.
How big should seedlings be before transplanting?
Seedlings should generally be around 2-4 inches tall with at least two sets of true leaves before transplanting.