Lactuca

Lactuca is a genus of wild and domesticated lettuce species, an annual in the Asteraceae family and native to various parts of the world, including sections of the United States and Canada. Several species of lettuce (L. floridana and L. sativa) are common in nurseries and landscapes and are very similar to sowthistle (Sonchus spp.). These species are annuals that prefer cool weather planting, but may also germinate in the spring or summer in irrigated nursery crops or landscapes. L. sativa, in particular, is a domesticated species familiar to home gardeners and includes the romaine, butter head, iceberg, and loose leaf lettuce types.The genus name comes from the Latin word lac meaning milk in obvious reference to the milky plant sap.

Lettuce is best grown in moist to wet soils in part shade to full shade, although some species such as L. sativa prefer full sun. The plants require constant moisture. They will remain in the wild by self-seeding and to control the spread of the plant, you should avoid letting plants go to seed.

Seedlings form a rosette of waxy leaves with variable, lobed leaf margins. Wild lettuce leaves are similar to sowthistle leaves but lack prickles on leaf margins. Depending on the species, plants can mature to 1 to 4 feet in height. In warm weather, plants can bolt and some species may reach 8 feet in height. Some species produce insignificant flowers that are pale yellow and form on branched heads. The seed head is similar to a dandelion but smaller.

Diseases, Insect Pests, and Other Plant Problems:

No serious insect or disease problems. Issues may include downy mildew, powdery mildew, shot hole, bottom rot, septoria leaf spot, Botrytis and wilt. Potential insect pests include aphids, snails, slugs, leafminers and whiteflies. Mosiac virus may appear.