American Wild Lettuce (Lactuca canadensis) vs Red Wood Lettuce (Lactuca hirsuta)
This guide is under construction and has not been published yet. It may have errors. When in doubt, double-check other sources for definitive ID.These two native lettuces are frequently confused. They look similar at a glance but are usually easily to distinguish by differences in pubescence, lobe shape, and length of involucres and seeds. L. canadensis ranges farther north, west, and southeast, is more tolerant of sun and moist conditions, and is much more common throughout its range. L. hirsuta is more shade-tolerant, but has a much more restricted range and is uncommon to rare in much of it, and is usually limited to dry, sandy or rocky woodlands in partial sun.
American Wild Lettuce (Lactuca canadensis) | Red Wood Lettuce (Lactuca hirsuta) |
A tall biennial native to eastern North America, having expanded its range westward as well. | An uncommon to rare biennial native to the eastern US, favoring dry, sandy or rocky woodlands. |
 Involucres (clusters of bracts under each flowerhead) are shorter, usually 10-12, sometimes to 15mm. Involucres usually look more stout. Photo © M.B., CC BY 4.0. |  Involucres are longer, usually 12-22mm. Involucres usually look narrower. Photo © Quinten Wiegersma, CC BY 4.0. |
 Seed bodies are shorter (2.5-3.5mm) and pappi (wispy part) are slightly shorter (5-6mm) Photo © Jennifer Aitkens, CC BY 4.0. |  Seed bodies are longer (4.5-6mm) and pappi are slightly longer (6.5-8mm, rarely to 10+mm) Photo © Quinten Wiegersma, CC BY 4.0. |
 Leaves and stems are rarely pubescent, and are usually glaucous (pale and waxy.) Photo © Ken Kneidel, Public Domain. |  Stem and leaves are usually noticeably pubescent (not always.) Photo © Nathan Aaron, CC BY 4.0. |
 Inflorescence is more compact and orderly, with most branches ascending, and flowerheads more densely-packed and more likely to point upwards. Photo © Alison Northup, CC BY 4.0. |  Inflorescence is wide and sparse, with long branches and scattered flowers, usually pointing in different directions. Photo © hr_dragonfly, CC BY 4.0. |
 When leaves are lobed, most side-lobes tend to be widest at the base and taper to a pointed tip. Photo © Quinten Wiegersma, CC BY 4.0. |  When leaves are lobed, most side-lobes tend to look more blocky, often becoming slightly wider from the base, the widest point being closer to the tip, and the tips averaging blunter. Photo © Quinten Wiegersma, CC BY 4.0. |
 Occurs in a wider range of habitats; can occur in full sun and on moister, richer sites. May occur on sites with dense ground-level vegetation. Photo © Skyler Principe, CC BY 4.0. |  Limited to partly-wooded, dry upland habitats with relatively poor, acidic, sandy or rocky soil. Vegetation is usually sparser where it occurs. Photo © stephen, CC BY 4.0. |
Additional Notes
As with other Lactuca species, both of these species are highly variable so it is crucial to consult multiple characteristics.FNA reports the involucres of L. hirsuta as 12-18+mm, whereas FSUS reports the length of fruiting involucres specifically as 12-22mm. Although the fruiting involucres may be more reliable, we still found pronounced average differences on the involucres at any stage of development, and some keys, like FNA, do not limit their measurements to the stage of fruiting.
Flower color is not reliable for telling these apart. Both species usually have rich yellow flowerheads, both can have a reddish tinge to the flowerheads on some plants, and both can rarely have bluish flowerheads.
References & External Resources
These short lists show only links helpful for ID. For a complete list of references and resources also covering other aspects of ecology, visit the links section of the full article on each plant, which is the first entry here.
