Hoophouse lettuce Green Forest and Red Salad Bowl. Photo by Wren Vile
I have written posts for Mother Earth about winter lettuce and Growing Lettuce Year Round, and I have a year (May to April) of postings about suitable lettuce varieties for each month on my website Sustainable Market Farming. The Lettuce Year Round article is mostly about scheduling your sowings to provide an unbroken supply of lettuce, no shortages or gluts, using succession planting techniques. Here I’m going to focus on varieties and strategies that work best early in the year.
I like to sow four lettuce varieties each time (for the attractive harvests, and to reduce the risks if one variety bolts or suffers disease): at least one red and one romaine. If you choose varieties with different numbers of days to maturity, you will stretch the harvest period (and get more choice each time you harvest).
We have 5 lettuce seasons, with different varieties:
- Early Spring (Jan – Mar), 6 sowings
- Spring (April – May 15), 5 sowings
- Summer (May 15 – Aug 15), 17 sowings
- Fall (Aug 15 – Sept 7), 9 sowings
- Winter indoors, Sept 8 – 27, 9 sowings
Each season has varieties that work well and others that do not. Our springs are short and quickly heat up, so we only have a small window for sowing lettuces that bolt as soon as the weather warms at all. Johnny's Selected Seeds has a head lettuce planting program with three seasons (early season, mid-season and late season) where they recommend some suitable varieties. Varieties for early spring are fast-growing. Mid-season varieties have some heat-tolerance (resistance to bolting). Late-season varieties are chosen for disease resistance and cold tolerance.
Growing early season lettuces involves choosing suitable types and varieties (cold-tolerant and fast-growing), having successful production methods, and a good schedule. Harvesting early in the year might mean fast production in January and February, or it might mean starting in the fall and overwintering the plants.
Our Cold-hardiness Plant Zone in central Virginia is 7a, which means our annual minimum temperature averages 0°F to 5°F (-18 to -15°C). The average date of the last spring frost is April 30 (later than 5/14 one year in 10). We grow lettuce outside from transplants from February to December, in a solar greenhouse from October to early March, and in a solar-heated double-layer hoophouse from October to April.
There are several different general types of lettuces. In terms of growing speed, the baby lettuce mixes and the leaf lettuces produce harvests soonest after sowing. Loose-leaf lettuces are very useful because you can harvest individual leaves while you’re waiting for the heads to reach full size.
Leaf types are ready for harvest 45-60 days from direct seeding, 30-45 days from transplanting. There are two different types of Butterhead lettuce: Boston (larger and fluffier) and Bibb (smaller). Bibbs mature in 60-75 days, most head lettuce need up to 80 days from seeding, or 60-70 days from transplanting in spring. Romaines are slower-growing (70 days or more). Batavian lettuces (also called French Crisp) are tasty, thick-leafed varieties that have excellent heat and cold tolerance. Icebergs mature in 75-100 days.
Bolt-resistance of lettuce generally goes from Leaf types (first to bolt), through Romaines, Butterheads, Bibbs, to Crispheads.
It’s important to grow the right lettuce variety for the conditions. For earliest harvests, consider the faster, varieties. Some of the early spring lettuce varieties are often useless in central Virginia if sown after mid-March, or even mid-February, because they bolt prematurely as the Virginia spring flips from cold to hot (and back again).
Varieties we only sow until 2/15 include leaf lettuces Bronze Arrowhead (46 days); Buckley, Ezrilla and Hampton (55d multi-leaf types); Merlot (60d), Midnight Ruffles (48d) and Oscarde (45d).
Antares (48d) Panisse (48d) and Revolution (38d) are leaf lettuces we can sow until 3/15.
Others that we like in early spring go on to be useful until mid-May too. In this category are Buttercrunch (a small 50d Bibb); Nancy (58d) and Sylvesta (52d) (two big green Bibbs); Pirat (55d red Bibb), Green Forest (56d), Kalura (57d) (two green Romaines); and New Red Fire (55d), our reliable Salad Bowl (45d) and Red Salad Bowl (46d), Starfighter (52d), and Swordleaf (53d) (leaf lettuces)
Looseleaf lettuces are very useful because you can harvest individual leaves off the whole row while you wait for the heads to reach full size. (Yes, you will be setting them back a bit, but there will be plenty of lettuce later and this method will give you lettuce sooner.)
Cold-tolerance of lettuce
Lettuce is more cold tolerant than many people realize. If plants are sufficiently hardened (prepared by growing in gradually lower temperatures), they can withstand freezing. Medium-sized plants with 4-10 leaves (Marvel of Four Seasons, Olga, Rouge d’Hiver, Tango, Winter Density may survive unprotected down to 15°F (-9.5°C). Half-grown lettuces are more cold-hardy than full-sized plants. Large leaves of some lettuce will die at 22°F (-6°C).
Crop Requirements of Lettuce
Lettuce seed remains dormant unless triggered by adequate levels of light and temperature. It needs light to germinate, so don’t sow too deep: ¼-3/8" (6-9 mm) is enough. Some sources recommend not covering the seed at all, but this can make it hard to keep the seed damp. The light dormancy is more pronounced in fresh seed, which has higher levels of the hormone that inhibits germination. Start the year using leftovers from the previous year! Sow a few extra seeds to hedge your bets.
Soil temperature is important. I have a table of optimum soil temperatures for germination in The Year-Round Hoophouse. The optimum temperature range for lettuce germination is 68-80°F (20-27°C). It takes 15 days to germinate with a soil temperature of 41°F (5°C), 7 days at 50°F (10°C) and only 4 days at 59°F (15°C). Even a few hours at temperatures higher than the optimum can induce dormancy - it's pointless to try to germinate lettuce in soils as warm as 86°F (30°C).
Lettuce transplants prefer a well-draining soil high in organic matter, and with a pH of 6.0-7.0, not lower. Optimum lettuce growing temperatures are 60-65°F (15-18°C), with a minimum of 40°F (4.5°C) for any growth to occur. Lack of water will lead to bolting, and/or bitterness. Keep them growing quickly for good flavor.
Growing Lettuce in January
We plan to start harvesting heads of lettuce outdoors from April 15. Before then we will harvesting lettuce in our greenhouse and hoophouse.
In mid-January we sow four hardy, fast-maturing lettuce varieties, to become our first outdoor transplants. Buttercrunch green Bibb lettuce is one of my favorites for early spring. One of the Salad Bowl lettuces, red or green, is also usually in my first sowing. The Salad Bowls are so reliable and productive! New Red Fire has become another reliable lettuce stand-by for us. It is more of a leaf lettuce, and doesn’t exactly head up, although it can be cut as admittedly lightweight heads. It works fine as a leaf lettuce, harvested by the cut-and-come-again method. We grow New Red Fire year round, it’s that adaptable and easy-going. We haven’t found many good full-size red Romaines. 'Bronze Arrow' has worked well for us and we have harvested it in early May.
We grow all our outdoor lettuce as transplants. In spring we sow in 3 inches (7.5cm) deep open wood seed flats, 12-by-24-inch (30 x 60cm). We make four little furrows by pressing a 12″ (30 cm) plastic strip (aka a ruler!) into the seed compost. We sow the seed, label it, cover it lightly, water, and put the seeded flats in our germinator cabinet. The first flat of the year takes about 9 days to germinate.
Once the seedlings are big enough to handle, we spot them out into 4 inches (10 cm) deep flats (also 12-by-24-inches/30 by 60cm). We have a plywood dibble board with pegs evenly spaced about 2.5 inches (6 cm) apart. We aim to harden off the lettuce for two weeks in the cold frame before transplanting into the garden beds with thick rowcover on hoops to protect the lettuce from the still-cold outdoors. To be ready for harvest 4/15, these seeds have to become full size lettuces in 88 chilly days.
Seeds can instead be sown in cell packs or plug flats, putting three seeds in each cell, and later reducing to one seedling with scissors. Cells or pots with diameters from 1-2½-inch (2.5-6cm) can be used. The 96-cell size (1x1½-inch/2.5x4cm) works well, although the 200-cell size (1 by 1 inch/2.5x2.5cm) is possible if you can be sure to get the transplants out before they get root-bound. Soil blocks are also possible, but take more time.
We make a second sowing on January 31. The intervals between sowings at the beginning of the year are long, because later sowings will catch up to some extent with earlier ones. Most crops grow faster in warmer weather.
February: We sow lettuce twice in February – mid-month and late-February. We continue to harvest leaves from the large lettuce we transplanted in the hoophouse in October.
March: We sow flats of lettuce every 10 days in March. March 9 is our outdoor transplanting date for our first 120 lettuce (about one week’s worth for 100 people).
April: We sow every 9 days in April, and the flats no longer do well in the germination chamber, where it is too hot. Instead, we simply set the seeded flats in the greenhouse, moving them to the coldframe about 14 days before we plant to plant them out.
After May 1, we move lettuce sowing outdoors and make a nursery seedbed, from where we will dig bare-root transplants.
Here is a link to a helpful publication from eXtension: Disease Management in Organic Lettuce Production. Horribly useful photos!
Pam Dawling works in the vegetable gardens at Twin Oaks Community in central Virginia. She often presents workshops at MOTHER EARTH NEWS Fairs, as well as sustainable agriculture conferences. Pam also writes for Growing for Market and other magazines. Her books, Sustainable Market Farming, and The Year-Round Hoophouse are available at www.sustainablemarketfarming.com. Read all of Pam's MOTHER EARTH NEWS posts here, and see her blog on her website and also on Facebook.com/SustainableMarketFarming.
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