Garden Detective

Growing iceberg lettuce takes time and cool weather

Iceberg lettuce has long been a California favorite. But it needs the right timing and weather for growing success in Sacramento.
Iceberg lettuce has long been a California favorite. But it needs the right timing and weather for growing success in Sacramento. Handout file

Experts tackle readers’ garden questions.

Q: We grow tomatoes and a few other veggies. However, we like iceberg lettuce. We would like to plant and grow our own. We would very much appreciate any and all pointers on the subject.

Joe Villanueva,

Citrus Heights

Sacramento County master gardener Cathryn Rakich: Iceberg lettuce (Lactuca sativa) is a cool-season annual that can be grown successfully in the Sacramento region; however, timing and weather are critical. Also known as crisphead lettuce, iceberg has a long growing season and distinct temperature requirements.

In the Central Valley, iceberg is best planted in mid-August to early September, but also can be planted as late as November. Late-summer plantings will take 70 to 80 days to harvest time. Late fall and winter plantings will take as long as 130 days.

Lettuce can be seeded directly or transplanted into the garden. If seeding, it is a good idea to plant more seeds than necessary to make up for low germination rate. Cover seeds with no more than one quarter inch soil. Transplants should be spaced 12 inches from each other.

The optimal growing temperatures are mid-70s during the day and mid-40s at night. Higher temperatures can cause bolting, bitterness and poor head formation. Freezing temperatures will slow growth and damage outer leaves.

Iceberg does best in loose, well-drained soil, but also can be grown in clay with good soil structure and adequate drainage. For optimal growth, the soil should remain evenly moist with frequent, light irrigations as the plants mature. Drip irrigation is preferred; water remaining after overhead watering could create favorable conditions for foliar pathogens. Splashing water will spread fungus spores.

Add a layer of organic mulch around the plants to help conserve soil moisture and discourage weeds. Because of its shallow root system, lettuce cannot go deep for nutrients so consider a light application of 5-10-10 fertilizer every three to four weeks to boost the nitrogen, phosphorus and potassium. Organic fertilizers such as manure tea, fish emulsion, bloodmeal and cottonseed meal can be applied.

Potential pests include snails, slugs, earwigs, aphids, leafminers, thrips and whiteflies. Because the delicate lettuce leaves can absorb insecticides, it is important to choose non-chemical controls such as hand picking snails, routinely removing infected foliage and applying organic repellants. Rabbit-proof fencing will discourage furry visitors.

For more information on growing lettuce, visit the University of California Integrated Pest Management website at http://ipm.ucanr.edu or check out “Vegetable Gardening 101” on the UC Master Gardeners of Sacramento County website at sacmg.ucanr.edu.

Cathryn Rakich is a UC Cooperative Extension master gardener for Sacramento County.

Garden questions?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to h&g@sacbee.com. Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:

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