Lactuca

( lak - TOO - kuh )

At-A-Glance Information

This genus is commonly known as Lettuce, and includes flowering annual herbaceous plant species that have a worldwide distribution, concentrated around temperate Europe. Plants in this species are commonly found growing wild in disturbed areas, and range in water and sunlight needs. They typically form basal rosettes of green foliage and can reach between 1 and 4 feet tall, producing branched flower infloresences in warm weather.

Lactuca Species and Varietals

The genus Lactuca is a member of the plant family Asteraceae, and includes between 50 and 75 distinct species. The genus name is derived from the Latin word lactuca, which means 'having milky sap'. Plants in this genus are closely related to Chicory and Dandelion. The best growing zones for Lactuca plants vary depending on the species grown. For more information, see the species descriptions below. To find your zone, click here: Zone Map.

Lactuca biennis (Tall Blue Lettuce, Blue Wood Lettuce)
Native to the United States and Canada, this species forms a biennial herbaceous plant that grows from a taproot to reach heights of between 20 inches and 13 feet tall. Leaves are deeply lobed and toothed. Flowers are white. This species grows best in USDA hardiness zones 3a-8b.

Lactuca canadensis (Canada Lettuce, Canada Wild Lettuce, Tall Lettuce)
This species is native to eastern and central areas of North America. It forms a biennial herbaceous plant that grows from a taproot to reach up to 80 inches tall or more. Flowers are yellow to pale yellow in color, with a similar look to Dandelion blooms. Young leaves and stems of these plants are edible and can be cooked and eaten as greens. This species thrives in USDA zones 3-5 and is considered invasive in regions of western North America and Eurasia.

Lactuca floridana (Woodland Lettuce, Florida Lettuce, False Lettuce, Florida Blue Lettuce)
These plants are native to North America, and reach between 3 and 8 feet tall when mature. They are typically unbranched, and have green foliage and a central light green to reddish-green stem. Flowers are blue to white in color and bloom from July through October in the plant's native range. The entire plant is edible and can be cooked and eaten as greens or leaf vegetables. Good in USDA zones 4a-8b.

Lactuca indica (Indian Lettuce, Tropical Lettuce, Yao Mak, Aki-No-No-Geshi)
This species, native to western China, the Himalayas, and southwestern Asia, is a widely introduced species around the globe. It forms a biennial herbaceous plant from an underground taproot, and typically reaches about 16 inches tall. Plants are commonly cultivated as animal fodder, but are also consumed as a leaf vegetable in some regions. Best in USDA zones 4a to 9b.

Lactuca sativa (Lettuce, Garden Lettuce, Cultivated Lettuce)
Plants in this species are mainly cultivated as leafy vegetables, commonly added fresh to salads, grilled or cooked. It is often grown as a hardy annual, requiring a good amount of cold temperatures to produce well. This species grows best in USDA zones 2a to 11b. There are many cultivars that have been developed within this species, listed and described below:

'Butterhead' (Boston, Bibb)
This variety has a loose head of green leaves, and is known for its sweet flavor and tender texture.

'Celtuce' (Stem)
This type is grown for its seedstalk, rather than its leaves, and is used primarily in Asian coking, stewed, or in creamed dishes.

'Iceberg' (Crisphead)
Very popular variety that gets its name due to the way it was transported; tops of heads could be seen above crushed ice. Low in nutrition and flavor.

'Leaf' (Looseleaf, Bunching)
This is the most widely cultivated variety of lettuce, and produces loosely bunched heads of green foliage. Used mainly for salads.

'Little Gem'
A dwarf or compact variety of Romaine lettuce, popularly cultivated in the United Kingdom.

'Oilseed'
This cultivar is grown for its seeds, which are pressed to extract their oil. Plants produce few leaves, and seeds that are 50% larger than other types.

'Red Leaf'
A group of lettuce types with red foliage, similar in taste and composition to 'Leaf' or 'Bunching' lettuce.

'Romaine' (Cos)
This variety is used mainly for salads and sandwiches, and forms long, upright heads of foliage. Great for Caesar salads.

'Summercrisp'
(Batavian, French Crisp)
Larger, bolt-resistant plants with crispy foliage. Great for salads.

Lactuca serriola (Prickly Lettuce, Milk Thistle, Compass Plant, Scaole)
These annual or biennial plants are commonly considered weeds in orchards and other areas with disturbed soil. It is native to Eurasia and north Africa, and has naturalized in many other areas around the globe. Stems are spineless and reddish, and contain a milky latex, reaching up to almost 7 feet tall. Leaves are waxy and greyish-green. Flower heads are yellow, often tinged with purple. Leaves can be consumed raw or cooked, though they have a somewhat bitter taste. Grows well in USDA zones 6-9. This species is considered highly invasive in North America, Australia, and regions of Europe.

Lactuca virosa (Bitter Lettuce, Opium Lettuce, Wild Lettuce)
This species reaches up to 2-6 feet tall when mature, and produces bright yellow, daisy-like flowers. Its common name 'Opium Lettuce' refers to the use of its milky white sap, which is harvested for its sedative properties. This species is considered invasive throughout Europe, southern North America, Australia, and Chile.

Caring for LActuca

Lactuca, or Lettuce, plants can either be grown from seed (direct-sown or started indoors) or purchased as starts from a reputable nursery. There are commonly seed packets available with a mix of lettuce cultivars to provide home gardeners with an array of colorful, tasty leaves to harvest throughout the growing season. Space loose-leaf varieties between 6 and 8 inches apart and head lettuce about 12 inches apart for best coverage and airflow. Seeds should be planted about 1/4 to 1/2 inch deep. If sowing seeds indoors, wait until seedlings have 3-4 true leaves before transplanting outdoors, which generally takes between 5 and 6 weeks' time.

Choose an area of the garden that receives full sun to light shade. These plants are considered cool-weather crops, and appreciate protection from high heat and intense sun. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 6.0 and 7.0 (slightly acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, most Lettuce varieties appreciate consistent waterings, especially if they are being continually harvested over the growing season. Mature plants typically need between 1 and 2 inches of water per week.

Fertilizing is not necessary, especially if you have prepared your garden soil well before planting. If local soils are particularly poor, an application of about an inch of compost over the growing area in late spring can ensure that plants have enough nutrients in their root zone to produce well through the rest of the season. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Pruning Lettuce plants is not necessary; loose-leaf varieties are harvested throughout the season, and head varieties are left to grow until harvested, and then outer leaves are removed. Towards the end of the growing season when temperatures rise, these plants will start to bolt, or produce their flower stems, which pulls nutrients and moisture away from basal foliage. Promptly remove any flowering stems as they emerge to prolong the harvest, unless you will be collecting seeds for propagation. Lettuce plants are typically composted at the end of the season and replaced in the next.

Harvesting Lactuca Plants
Lettuce, both wild and domesticated types, are harvested for their edible foliage. Depending on their growth habit, they are harvested in two main ways: by cutting the entire head off of the plant at its base or by harvesting individual leaves every few days during the active growing season. Head Lettuce, which includes popular varieties such as Romaine and Iceberg, is left to grow until fully mature (which typically takes between 70 and 80 days). Heads should be firm when gently squeezed. Cut the entire head of leaves off at its base just above the soil line using a sharp, clean knife. The head can then be brought inside and processed. For loose-leaf varieties, which are colloquially referred to as 'Cut and Come Again' lettuces, first identify mature, outer leaves that are large enough for eating. Then, using clean, sharpened scissors or a knife, remove the leaf 1-2 inches above the soil line, leaving the center of the plant intact. Be very careful to not damage any of the other leaves or the crown, as this will invite disease and other issues. Loose leaf lettuce can be harvested every few days to weekly to allow for new leaves to mature. To keep backyard-harvested lettuce fresh for an extended period, first bring it indoors. Wash leaves in cool water and then dry thoroughly. Wrap them in paper towels, and then store them in an airtight plastic bag in the crisper drawer of the refrigerator. The main goal is to minimize moisture and exposure to air, which leads to wilting and spoilage. This processing can be completed with both loose-leaf and head varieties.

Disclaimer: Information contained on this website is strictly and categorically intended as a reference to be used in conjunction with experts in your area. Foraging and consumption of plant parts should never begin without the guidance and approval of a local plant specialist. The providers of this website accept no liability for the use or misuse of information contained in this website.

Propagation

Lactuca, or Lettuce, plants are annuals, and therefore are typically propagated through collecting and sowing seed. When growing Lactuca plants from seed, just keep in mind that the resulting plant may not be an exact genetic match to the one that produced the seeds. For seeds that will emerge true to type, purchase them from a reputable seed vendor. To propagate your Lettuce plants, follow the instructions below.

Propagating Lactuca by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. The seed heads on plants are pretty easy to spot, they're left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will continue to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Get your container prepared. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 2-6 weeks from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 65 and 72 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Lactuca seed heads emerge after flowers have faded. Seeds have feathery attachments that assist them in traveling away from the parent plant.

Lactuca seeds are small and linear. They range in color from tan to brown to almost black.

Problems and Pests

Certain species of Lactuca are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. Lactuca plants can suffer from issues with the following pests and diseases in the landscape: