Growing Lettuce Year Round
Lettuce is generally considered a cool weather plant, grown in early spring or fall, although it can be grown in the warm season in most of the SF Bay Area by choosing varieties adapted to warmer weather. Check seed catalogs for summer lettuces.
Lettuce does best in a loose, well-drained soil, with regular watering and adequate nitrogen. Whether your soil is heavy clay or a light sandy type, the incorporation of compost will often improve the growing conditions. Homemade compost is ideal, with municipal compost made from green waste recycling being the next best. Dig thoroughly in 1-3" of compost with a shovel or spading fork to a depth of 6-8", shape the bed and level it. Just before planting, add a nitrogen fertilizer where the transplants will be planted according to fertilizer label recommendations. Good sources of organic nitrogen include alfalfa meal (my favorite), cottonseed meal, fish and/or kelp meal, as well as blood and feather meal. I have found the latter two attract dogs that try to eat the animal products, soil and all.
The best time to transplant is the late afternoon or on an overcast day. If transplanted in hot weather, the seedlings will need some shade protection for the first few days. To transplant, carefully remove each plant from its container by pushing the bottom of the six pack cells and lift small plants by the leaves. If the roots are at all matted, gently separate and spread them out. Set transplant slightly (1/2” or so) higher than the soil level into which it is being planted. Firmly press the soil around the rootball, making sure not to cover container soil with the garden soil but so they are nearly level with each other.
Water in thoroughly. Thoroughly means watering 2 – 3 times as long as you expect it should take, as water moves into and through soil much more slowly than you think. An application of liquid fertilizer may be helpful 1-2 weeks after transplanting, as the organic nitrogen may not become available for several weeks. Plant seedlings approximately 4-6" apart so that you may eat the thinnings at the point you thin to the final distance of 8”-10” apart.
Lettuce will be crisper if harvested in the early morning. Immediately after picking, wash thoroughly and get the excess moisture out. This can easily be done by placing freshly washed lettuce in a clean dish towel, hold cloth by four corners, going outside and fling in semi circle arc until water no longer flies off. Store in a plastic bag wrapped in the dishtowel to create a humid environment. Pick loose-leaf lettuce from the outside, letting the inner leaves continue to grow. Heading types such as romaine, Batavian and butterhead are usually pulled up whole, but these can also be picked outer leaves first until head begins to form.
Types and Varieties of Lettuces
There are several major types of lettuce which include: butterhead, cos (syn 'romaine'), loose-leaf, crisphead or icebergs and Batavian or summercrisp. Cos lettuce is very upright and columnar, forming a particularly sweet creamy white, crisp heart, surrounded by sturdy outer leaves. It is fairly demanding to grow in terms of being unforgiving of poor conditions and poorly adapted to hot weather. The crispheads are the slowest to bolt, then summercrisps, butterheads, leaf lettuces, and finally, cos types.
My favorite is the French Batavian or summercrisp, a lesser-known type. Although differences exist between the varieties, overall it is intermediate between the crisphead and the loose-leaf lettuce. The outer leaves are thick, crunchy and flavorful with the loosely heading, often conic-shaped heart being buttery and sweet. These are quite large lettuces, and need good fertility. The butterhead types have thick, buttery, soft and succulent sweet leaves that form a loose head at maturity. There are more than a hundred different varieties of lettuces, with 30 or so commonly available through retail garden seed catalogs. The following are descriptions of some highly rated varieties.
- Black Seeded Simpson. Light green, broad-leafed loose-leaf type. Early, fast growing large plant with mild, sweet, juicy softly crinkled leaves. Very heat and bolt resistant, rarely getting bitter.
- Cardinale. This Batavian lettuce shimmers with red-purple beauty in climates with lots of sunshine and cool evenings. Its sturdy yet pliable leaf is bordered by mini-scallops. Perfect for salad mixes because of its sweet flavor and its beautiful color is a real plus.
- Darkland Cos. This is a superior, darkest green, disease resistant romaine, offering a wonderful sweet flavor. When planted 6" to 8" apart, it produces compact ‘hearts of romaine’. Yields large, full-sized heads.
- Loma. This stunning apple green Batavia was bred for the baby leaf market but is great grown to maturity. Each sweet-flavored crunchy leaf at about the 3" stage has perfect scallops on the edge in addition to being sturdy and pliable. Not only is it perfectly suited for baby leaf use, it forms lovely mini- and full-sized heads. Each leaf has an interesting character of its own.
- Majestic Red. A red romaine variety with savoyed leaves. The color is ruby bronze with a bright green under leaf.
- Marvel of Four Seasons. Remarkable in both color and texture. The crisp ribs of the sparkling burgundy outer leaves contrast wonderfully with the tender pink and cream interior. Reliable, easy-to-grow red butter lettuce.
- Nevada. A lovely swirl of sweet, nutty flavored bright green leaves, this green Batavia version of Sierra is very resistant to bolting and highly recommended for growing under the most difficult conditions. Nevada offers outstanding resistance to tipburn, bottom rot, and bolting.
- Sierra. This Batavian type has an open head, rich green, with a bronze tinge at the leaf margins. It is a delicious and very reliable producer with excellent heat tolerance. One of my favorites!
Pests and Diseases
Lettuce may get occasional pests including cutworms, foliage feeding caterpillars, aphids, snails and slugs. Caterpillars are most safely controlled with a biological insecticide called Bacillus thuringiensis, which goes by different brand names such as Thuricide, Bt and Dipel. Snails and slugs can be trapped through use of beer placed in saucers around the garden or by using a product having the brand name of Sluggo or Escar-Go, which is an iron phosphate containing bait. Both have low toxicity to pets and the environment.
By Nancy Garrison, Former Urban Horticulture and Master Gardener Program Coordinator