I hail from the lettuce capital of the nation, Salinas, California. The daytime highs in July and August are in the upper 60's with an afternoon wind blowing off the cold Pacific Ocean. Summertime lows are typically in the 40s but can dip into the upper 30s. Lettuce thrives there.
Native to the eastern Mediterranean, lettuce has been cultivated since Old Testament times. Back then there was only romaine, but the Romans had nine varieties of it. They believed it to have a calming effect and ate it at the beginning of meals to aid digestion.
Today we enjoy three types of lettuce. Romaine is still with us and is the most nutritious, a good source of iron and calcium as well as vitamins A, C and E.
Looseleaf, non-heading lettuces such as butter lettuce, with their rosette of fringed or
curling leaves, are great as cut-and-come again selections. Head lettuces such as Boston and Bibb have thick, soft, textured leaves. Crispy iceberg lettuce is a relatively recent introduction.
Now is the time to plant lettuce here. The optimal soil temperature for germination is 60 to 70 degrees, but lettuce will sprout in soil temperatures as low as 40 degrees. Romaine and iceberg lettuce can be grown from transplants, but the others grow from direct seeding. Avoid excess nitrogen and phosphorus to prevent tip burn. This crop will tolerate light shade but prefers full sun. Once temperatures reach 75 degrees, lettuce becomes bitter and goes to seed.
Harvest loose leaf lettuces about a quarter of an inch above the base to promote regrowth. Heads will keep in the refrigerator for two to three weeks if unwashed.
I have heard that Thomas Jefferson grew head lettuce in the summer. He would have eaten it boiled with some sort of sauce to offset the bitterness. After World War II, technological advances in refrigeration coupled with the development of the interstate highway system have made this cool-season crop available year round.
I'd like to share a dressing recipe which is popular in parts of the Midwest.
3/4 cup salad or olive oil 1/4 teaspoon dry mustard
1/4 cup lemon juice or cider vinegar 1/4 teaspoon pepper
1/2 can condensed tomato soup 1/2 teaspoon marjoram
1 tablespoon sugar 1/4 teaspoon paprika
1 tablespoon chopped onion 3/4 teaspoon salt
Blend all ingredients until smooth and enjoy. Refrigerate unused portion.
Master Gardener Ann Bartlett never lets lack of experience with a plant stop her from trying it in the ornamental beds around her home.