Canada Lettuce, Tall Lettuce, Tall Wild Lettuce

Lactuca canadensis 

lak-TOO-kuh  ka-na-DEN-sis

Synonyms of Lactuca canadensis (38) (Updated on 12-2-23 from Plants of the World Online): Agathyrsus acuminatus (Willd.) Sweet, Cicerbita canadensis Wallr., Cicerbita elongata Wallr., Galathenium elongatum Nutt., Galathenium integrifolium Nutt., Galathenium salicifolium Nutt., Lactuca canadensis var. albocaerulea Farw., Lactuca canadensis f. albocaerulea (Farw.) Farw., Lactuca canadensis f. angustata Wiegand, Lactuca canadensis var. angustifolia Kuntze, Lactuca canadensis f. angustipes Wiegand, Lactuca canadensis f. angustipes Farw., Lactuca canadensis var. elongata Farw., Lactuca canadensis f. exauriculata Wiegand, Lactuca canadensis var. laciniata Farw., Lactuca canadensis var. latifolia Kuntze, Lactuca canadensis var. longifolia Farw., Lactuca canadensis var. montana Britton, Lactuca canadensis var. obovata Wiegand, Lactuca canadensis f. pallida Farw., Lactuca canadensis var. spinulosa Jenn., Lactuca canadensis f. spinulosa (Jenn.) F.Seym., Lactuca canadensis f. steelei (Britton) Fernald, Lactuca canadensis f. stenopoda Wiegand, Lactuca canadensis var. typica Wiegand, Lactuca canadensis f. villicaulis Fernald, Lactuca caroliniana Walter, Lactuca elongata Mulh. ex Willd., Lactuca elongata var. longifolia (Michx.) Torr. & A.Gray, Lactuca longifolia Michx., Lactuca procera Schrad. ex DC., Lactuca sagittifolia Elliott, Lactuca steelei Britton, Lactuca villosa Muhl. ex Torr. & A.Gray, Mulgedium canadensis (L.) Farw., Mulgedium integrifolium Cass., Sonchus pallidus Willd., Wiestia canadensis Sch.Bip., Wiestia elongata Sch.Bip.

Lactuca canadensis L. is the accepted scientific name for Canada Lettuce. The genus and species were named and described as such by Carl von Linnaeus in the second volume of the first edition of Species Plantarum in 1753.

As of 12-2-23 when this page was last updated, Plants of the World Online lists 114 species in the Lactuca genus. Lactuca is a member of the plant family Asteraceae with 1,702 genera. Those numbers could change as updates are made on POWO. The number of genera in this family fluctuates quite often.

The above distribution map for Lactuca canadensis is from Plants of the World Online. The map on the USDA Plants Database is similar.

The map on iNaturalist shows where members have made observations. Anyone can join and it is a great website to confirm and share your observations. The maps on iNaturalist are continually updated as members post new observations.

THERE ARE SEVERAL LINKS AT THE BOTTOM OF THE PAGE FOR FURTHER READING AND FOR BETTER PLANT ID.

Lactuca canadensis is quite common on the farm and along roadsides in the surrounding countryside. It is quite common in yards, along fences, ditches, homes… You get the picture. Some plants get very tall with large stems while others are smaller which depends on their growing conditions. Several species in the genus are quite similar.

Unbranched biennial plants grow to 3-8’ tall with deep taproots. The roots, stems, and leaves have white latex. Plants prefer a sunny location in moist to slightly dry soil. Plants growing in rich, slightly moist soil will produce larger plants. The bigger plants on the farm grow in the southeast back pasture near the swampy area.

The leaves grow alternately along the stem and can be light to dark green, have purplish edges, and can have a yellowish tint. The largest leaves can grow around 10” long x 3’ wide, and are lanceolate-oblong.

The longest leaves have deep pinnate lobes while the smaller leaves may have shallow lobes or have no lobes at all.

The cylindrical (terete), hairless (glabrous) stems can be light green, reddish-green, and can also have purple streaks. They can also have a bluish hue…

Lactuca canadensis is a highly variable species and I don’t think any two plants are alike.

The leaves of some plants have short, fine hairs along the margins on the undersides of the central veins.

This is a good photo of the involucral bracts that surround the flowers.

Stems terminate in a multi-branched inflorescence, up to 2’ long, with multiple heads.

This plant has NUMEROUS deeply lobed leaves.

The stem is more maroon…

Several plants always grow in the fence row along the front pasture. Plants in this area are in full sun with dryer soil during the summer so their leaves are usually long and narrow…

 

 

 

 

Several aphid species use Lactuca as a host plant. Goldfinches occasionally eat their seeds. Rabbits eat the leaves of first-year plants while deer and livestock eat the top leaves of the plants. 

The small flowers consist of 12-25 yellow to slightly reddish-orange ray florets. The florets (petals) are surrounded by numerous light green (sometimes purple or red-tinted) bracts (phyllaries, involucral bracts). The flowers are unscented. I hoped to get some good photos of the flowers while they were open but it was useless… Maybe someday.

Numerous types of bees and flies feed on the nectar and pollen. Caterpillars of several moths feed on the plant’s florets. Many spiders build webs in the inflorescence.

The flowers are replaced by dark brown seeds (achenes) with tufts of hair that are attached to each other by thread-like beaks. These hairs allow the seed to float through the air… 

A Lactuca canadensis decided to come up in front of the Canna bed in 2020. I decided to leave it be so I could watch I grow but the next thing I knew the plant had bent over.

I will continue adding more photos and information as time goes by.

I have enjoyed photographing and learning about the many wildflowers growing on the farm and other areas. The farm is located in Windsor, Missouri in Pettis County (Henry County is across the street and Benton and Johnson aren’t far away). I have grown over 500 different plants and identified over 250 species of wildflowers (most have pages listed on the right side of the blog). I am not an expert, botanist, or horticulturalist. I just like growing, photographing and writing about my experience. I rely on several websites for ID and a horticulturalist I contact if I cannot figure them out. Wildflowers can be somewhat variable from location to location, so sometimes it gets a bit confusing. If you see I have made an error, please let me know so I can correct what I have written.

I hope you found this page useful and be sure to check the links below for more information. They were written by experts and provide much more information. Some sites may not be up-to-date but they are always a work in progress. If you can, I would appreciate it if you would click on the “Like” below and leave a comment. It helps us bloggers stay motivated. You can also send an email to me at thebelmontrooster@yahoo.com. I would enjoy hearing from you especially if you notice something is a bit whacky.

FOR FURTHER READING:
PLANTS OF THE WORLD ONLINE (GENUS/SPECIES)
INTERNATIONAL PLANT NAMES INDEX (GENUS/SPECIES)
TROPICOS (GENUS/SPECIES)
FLORA OF NORTH AMERICA (GENUS/SPECIES)
WORLD FLORA ONLINE (GENUS/SPECIES)
WIKIPEDIA (GENUS/SPECIES)
DAVE’S GARDEN
MISSOURI PLANTS
iNATURALIST
WILDFLOWER SEARCH
USDA PLANTS DATABASE
ILLINOIS WILDFLOWERS
MINNESOTA WILDFLOWERS
LADY BIRD JOHNSON WILDFLOWER CENTER
KANSAS WILDFLOWERS AND GRASSES
PFAF (PLANTS FOR A FUTURE)
GO BOTANY
FLORA FINDER
FRIENDS OF THE WILDFLOWER GARDEN
BACKYARD NATURE

NOTE: The data (figures, maps, accepted names, etc.) may not match on these websites. It depends on when and how they make updates and when their sources make updates. Some websites have hundreds and even many thousands of species to keep up with. Accepted scientific names change periodically and it can be hard to keep with as well. Some of the links may use a name that is a synonym on other sites. In my opinion, Plants of the World Online by Kew is one of the most reliable and up-to-date plant databases and they make updates on a regular basis. I make updates “at least” once a year and when I write new pages or add new photos but I do get behind. We are all a work in progress. 🙂