''Lactuca biennis'' is a North American species of
wild lettuce known by the common names tall blue lettuce and blue wood lettuce. It is widespread across much of the United States and Canada from
Alaska and
Yukon south as far as
California,
New Mexico, and
Georgia.
Biota of North America Program 2014 state-level distribution map
/ref>
''Lactuca biennis'' is a biennial herb in the dandelion tribe within the daisy family
The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...
growing from a taproot to heights anywhere from one half to four meters (20 inches to over 13 feet). There are deeply lobed, toothed leaves all along the stem. The top of the stem bears a multibranched inflorescence with many flower heads
A pseudanthium (Greek for "false flower"; ) is an inflorescence that resembles a flower. The word is sometimes used for other structures that are neither a true flower nor a true inflorescence. Examples of pseudanthia include flower heads, compos ...
. Each head is just over a centimeter (0.4 inches) wide and has many whitish to light blue ray florets but no disc florets. The fruit is a mottled achene
An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not ope ...
about half a centimeter (0.2 inches) long with a brownish pappus.
''Lactuca biennis'' was described botanically in 1794, with the name ''Sonchus biennis'', then transferred to ''Lactuca'' in 1940.
References
External links
Jepson Manual Treatment, University of CaliforniaCalphotos Photo gallery, University of California
biennis
Flora of North America
Plants described in 1794
{{Cichorieae-stub