Transformational Gardening

Tall Blue Lettuce (Lactuca biennis): Images

Date Location Notes Images
August 10, 2010 Southeastern, New Hampshire Tall Blue Lettuce is a biennial with clusters of bluish white flowers near the top when it goes to flower in August. The leaves are toothed or pinnately divided and the margins of the leaf are sparsely prickled. The leaves often terminate in an arrowhead shape unlike Canada Lettuce (Lactuca canadensis). Tall Blue Lettuce has scattered hairs on the underside of the leaf, especially the leaf center vein, but not like the stiff spiney hairs found on the center vein of the underside of Prickly Lettuce (Lactuca serriola) leaves.

Fortunately, all of the commonly-found sow thistles, Perennial sowthistle (Sonchus arvensis), Common (Annual) Sowthistle (Sonchus oleraceus) and Spiney Sowthistle (Sonchus asper) have yellow flowers, so I could be sure that this was not a sow thistle. Canada Lettuce (Lactuca canadensis) and Prickly Lettuce (Lactuca serriola) also have yellow flowers. By eliminating all other possibilities, I was able to confirm that this plant is Tall Blue Lettuce.
Date Location Notes Images
April 6, 2012 Southeastern, New Hampshire Tall Blue Lettuce rossette. Notice that there is white sap coming from a cut leaf. Also, the leaf cross-section is triangular which differentiates it from Dandelion (Taraxicum), Chicory (Cichorium) and Cat’s Ear (Hypochaeris) species which all have rounded hump cross-section of the leaf stem. Erect hairs on the back of the leaf midrib differentiates it from Sowthistle (Sonchus) species. Also helpful with identification is that a few Tall Blue Lettuce plants come up there every year.
Date Location Notes Images
July 19, 2012 Southeastern, New Hampshire