Lettuce
Lactuca sativa
Asteraceae · sunflower family
Origin · Mediterranean · Western Asia
- Matures
- 1–3 months
- Harvest
- Over a period · Annual
- Sun
- 4–8 hrs
- Spacing
- 4–12 in
Planting window
When to sow, by microclimate — foggier blocks run a different calendar than sunnier ones.
| Jan | Feb | Mar | Apr | May | Jun | |
|---|---|---|---|---|---|---|
| Foggy | ● | ● | ● | ● | ● | ● |
| Sunny | ● | ● | ● | ● | ● | ● |
| Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|
| Foggy | ● | ● | ● | ● | ● | ● |
| Sunny | ● | ● | ● | ● | ● | ● |
Sunlight
How well it does at each level of direct sun per day.
Soil depth
Root room it needs — useful for sizing raised beds and containers.
Soil pH
The soil acidity it grows best in — most crops sit just below neutral, so this mostly matters for heavily amended or long-reused beds.
- Preferred range
- pH 6.0–6.5
Spacing
Room each plant needs — along the row and between rows — for sizing beds.
- In-row
- 4–12 in
- Between rows
- 12 in
Growth habit
The shape it makes in the bed and how tall it gets — what tells you whether to give it a trellis, a stake, or just room.
- Habit
- Low mound
- Mature height
- 6–12 in
Low and self-supporting — no staking needed.
Growing in containers
Whether it does well in a pot, planter, or window box — the SF balcony-and-deck question, weighing its footprint, form, and staying power, not just root depth.
Happy in a pot, planter, or window box — no garden bed required.
How to start it
Sow it where it grows, or raise it under cover and set it out — and how far ahead to start the seedlings if it's the latter.
- Usually
- Direct-sow
- Start indoors
- 4 weeks ahead
Sown straight into the bed it will grow in.
Getting started
How it goes in the ground — how deep to sow or set it, and the soil temperature it needs to wake up. The cold-soil floor is the real limiter for direct-sowing in a foggy SF spring.
- Started from
- From seed
- Ideal soil temp
- 60–75°F
- Sow depth
- 0.25 in
- Time to emerge
- 3–4 days
Germinates between 32–85°F; happiest around 60–75°F.
Watering & feeding
How thirsty and how hungry it is — the water it wants and how much feeding the bed needs to keep it producing. In the fog belt even a thirsty crop drinks less than it would inland.
- Water need
- Moderate
- Feeding
- Heavy feeder
Wants steady, even moisture — roughly an inch a week, a little more in a heat spell.
Hungry — enrich the bed well before planting and feed through the season to keep it going.
Sensitive to swings — keep steadily moist or leaves toughen, heads stall and edges brown (tipburn). A heavy feeder for fast, tender leaves.
Pests & diseases
What tends to trouble this crop — what it is, what you'll see, and what to do about it, least-toxic first.
Pests9
Aphids
- What it is
- Aphids have soft pear-shaped bodies with long legs and antennae and may be green, yellow, brown, red, or black depending on the species and the plants they feed on. A few species appear waxy or woolly due to the secretion of a waxy white or gray substance over their body surface.
- What you'll see
- Low to moderate numbers of leaf-feeding aphids aren't usually damaging in gardens or on trees. However, large populations can turn leaves yellow and stunt shoots; aphids can also produce large quantities of a sticky exudate known as honeydew, which often turns black with the growth of a sooty mold fungus.
- What to do
- Before planting vegetables, check surrounding areas for sources of aphids and remove these sources. On the other hand, these aphid-infested weeds can sometimes provide an early source of aphid natural enemies.
Armyworms
- What it is
- Armyworm larvae feed in groups, which distinguishes them from other vegetable pests such as corn earworms and loopers. Markings on newly hatched armyworms are usually hard to distinguish from those of other caterpillars; older larvae have distinct lengthwise stripes.
- What you'll see
- Armyworms may feed on the crowns of seedlings. On larger plants, armyworm caterpillars skeletonize leaves.
- What to do
- Handpick. Virus diseases, parasites (Hyposoter and Trichogramma), and general predators may be effective on caterpillars.
Corn Earworm or Tomato Fruitworm
- What it is
- The corn earworm or tomato fruitworm is a common caterpillar pest of many vegetables and flowers. Newly hatched larvae have several rows of dark bristles on their backs.
- What you'll see
- Earworms feed on leaves, buds, and flowers of many vegetable crops. They destroy seedlings, bore into lettuce heads and bean pods, make deep watery cavities in fruit, and leave frass.
- What to do
- Handpick, and avoid spraying with insecticides. Bacillus thuringiensis may kill 40 to 60% of the population but must be applied just after eggs hatch and before caterpillars enter fruit.
Cutworms
- What it is
- Cutworms are dull brown caterpillars ranging in length from 1 to 2 inches when fully grown. They curl into a C-shape when disturbed.
- What you'll see
- Cutworms feed on blossoms and leaves of many ornamental plants and attack most garden crops. They clip off seedling stems near or just below the soil level.
- What to do
- Cutworms are pests mainly in the spring. Destroy crop residues; keep garden weed-free in winter.
Flea Beetles
- What it is
- Their small size, enlarged back legs, characteristic shot-hole damage, and habit of jumping when disturbed make flea beetles easy to identify. There are numerous flea beetle species.
- What you'll see
- Adults feed mostly on leaves, leaving tiny pits or small holes at their feeding sites. Flea beetles feeding together can cover leaves with bleached, pitted areas or ragged holes.
- What to do
- Remove debris in the fall to remove any overwintering beetles. Reflective mulches applied very soon after planting and before plants become infected can be helpful.
Loopers
- What it is
- Loopers are green caterpillars with several white stripes down their backs. They arch their backs as they crawl, this looping movement giving them their name.
- What you'll see
- Loopers eat irregular holes in leaves, most often older leaves. They may also bore holes in lettuce and cabbage heads or damage fruit.
- What to do
- Handpick. Apply Bacillus thuringiensis or spinosad; they are effective against loopers, especially when caterpillars are small.
Snails and Slugs
- What you'll see
- Snails and slugs feed on a variety of living plants and on decaying plant matter. They create irregular holes with smooth edges on leaves and flowers by scraping with their rasp-like tongues.
- What to do
- It will not be possible to eliminate some shelters, such as low ledges on fences, the undersides of wooden decks, and water meter boxes, so make a regular practice of trapping and removing snails and slugs from these areas. The survivors congregate in the remaining shelters, where you can more easily locate and remove them.
Vegetable Leafminers
- What it is
- Adult leafminers are small, active, black flies often with a prominent yellow triangle between the bases of the wings. The head behind the eyes is mostly black.
- What you'll see
- Leafminers attack many different vegetable and flower hosts, including cole crops, cucurbits, tomatoes, peas, beans, aster, begonia, dahlia, impatiens, lily, marigold, petunia, and verbena. Adult female leafminers puncture leaves and sometimes petals to feed on exuding sap.
- What to do
- Leafminers rarely require treatment in gardens. Clip off and remove older infested leaves.
Whiteflies
- What you'll see
- Whiteflies use their piercing, needlelike mouthparts to suck sap from phloem, the food-conducting tissues in plant stems and leaves. Large populations can cause leaves to turn yellow, appear dry, or fall off plants.
- What to do
- Whiteflies have many natural enemies, and outbreaks frequently occur when these natural enemies have been disturbed or destroyed by pesticides, dust buildup, or other factors. General predators include lacewings, bigeyed bugs, and minute pirate bugs.
Diseases6
Big Vein of Lettuce
- What you'll see
- Big vein disease is a viruslike disease that causes the veins in leaves to become very enlarged and clear. Such deformities are easily seen if the leaf is examined with the light source behind it.
- What to do
- Lettuce big vein is caused by a viruslike agent vectored by the fungus Olpidium. Avoid fine-textured, poorly drained soils where big vein has been a problem.
Botrytis Rot (Gray Mold) on Lettuce
- What it is
- Symptoms of Botrytis crown rot are similar to sclerotinia rot: lower leaves of plants infected with Botrytis yellow, and eventually the whole head wilts and rots. A watery, brown decay develops on the underside of the head at the crown.
- What you'll see
- Leaves on or near the soil or in the dampest areas of the garden turn light brown and develop a gray or brown fuzzy growth of fungal spores. Plants shrivel and rot and often develop flattened hard black masses, called sclerotia, under rotted parts.
- What to do
- Plant on well-drained, raised beds, use furrow irrigation whenever possible, and try to keep the surface of vegetable beds as dry as possible. Remove diseased plants as soon as they appear and dispose of them.
Downy Mildew on Lettuce
- What it is
- Downy mildew gets its name from the downy masses of spores it produces on undersides of affected leaves. These downy growths initially may be confused with those of powdery mildew.
- What you'll see
- Downy mildew causes light green to yellow angular spots on the upper surfaces of leaves. White fluffy growth of the fungus develops on the underside.
- What to do
- The best way to prevent downy mildew is to avoid the environmental conditions that favor it. Destroy infected crop debris and susceptible related weeds before planting a new crop.
Powdery Mildew on Lettuce
- What it is
- Powdery mildew is often confused with downy mildew. Both downy mildew and powdery mildew produce whitish collections of spores on the leaf surface, but similarities end there.
- What you'll see
- Powdery mildew usually appears first as yellow spots on the upper leaf surface of older leaves; these spots develop the characteristic powdery growth and symptoms spread to the undersides of leaves and stems. Affected leaves may turn completely yellow and die.
- What to do
- Powdery mildew rarely becomes serious enough to require treatment. Powdery growth of powdery mildew.
Spinach and Lettuce Virus Diseases
- What you'll see
- Beet western yellows, Curly top, Cucumber mosaic, Lettuce infectious yellows, and Lettuce mosaic Many viruses are difficult to distinguish from one another by symptom alone. In addition, for each particular disease, the symptoms will vary greatly depending on stage of plant at time of infection and other factors.
- What to do
- Buy and plant virus-free seed if available. Resistant varieties may be available.
White Mold (Sclerotinia Lettuce Drop)
- What you'll see
- White mold is a distinctive disease that most often affects stems and foliage at the base of cole crops and lettuce plants. Affected tissue develops a soft, watery rot and white, cottony mycelium forms on the surface.
- What to do
- White mold is favored by a wet soil surface. Remove and destroy entire infected plants and crop residues as soon as you see the mold.
Harvest & storage
How to tell it's ready to pick, and how to keep it once it's in.
- Keeps
- WeeksHolds a week or two in the fridge.
- Ready to harvest
- Cut leaves 3-4 in long without cutting into the crown and it will regrow — you can cut three or four times; or take the whole head.
- Storing
- Refrigerate in the crisper; a head keeps a week or more, loose leaves a few days.
Culinary use & nutrition
What it's for in the kitchen, and the nutrients a 100 g raw serving is a notable source of.
In the kitchen
- Raw
Nutrition highlights
- Excellent source
- Vitamin K, Vitamin A
- Good source
- Manganese, Vitamin C
Share of the Daily Value in a 100 g raw serving (USDA FoodData Central).
Pollinators & wildlife
What this crop offers the garden's wildlife once it flowers — often the payoff for letting a bolting plant stand.
No notable draw for pollinators — its flowers offer them little.
Bolted lettuce does throw a spray of small yellow flowers, but they hold little reachable pollen or nectar and draw few visitors beyond the odd sweat bee.
Companion planting
What grows well nearby, and what to keep apart.
No research-backed companion pairings for this crop — folk pairings without evidence are left out on purpose.
Quick and shallow-rooted — a natural early crop to slot in ahead of heat-lovers like peppers and tomatoes, working the bed twice before summer.
Sources
Growing data on this page is drawn from UC Master Gardeners, San Mateo–SF Counties, Golden Gate Gardening (Pam Peirce), and the other references on our sources page.