Iowa wildflower Wednesday: Tall blue lettuce (Blue wood lettuce)

Over the last few years, this weekly series has inspired me to visit many natural areas for the first time on the hunt for new (to me) Iowa wildflowers, such as wild blue sage, dwarf larkspur, and wood betony. Today’s featured plant was hiding in plain sight, barely a quarter-mile from my home. I’d noticed it before this summer, but for some reason assumed it wasn’t native and never learned its name until a couple of months ago.

Tall blue lettuce (Lactuca biennis) is native to most of Canada and the United States. Sometimes called blue wood lettuce, biennial blue lettuce or woodland lettuce, the plant thrives in shady, wet habitats, including woods, swamps, and stream banks. I took all of the enclosed pictures on the Windsor Heights and Urbandale bike trails, which run along North Walnut Creek.

For botanically accurate descriptions of tall blue lettuce foliage, flowers, and seeds, I recommend the websites Minnesota Wildflowers,, or Friends of the Eloise Butler Wildflower Garden. According to the Lady Bird Johnson Wildflower Center at the University of Texas, the roots and sap of tall blue lettuce have had some traditional medicinal uses, but “people with sensitive skin […] may develop rashes from contact with lettuce sap.”

Like many summer wildflowers including ragweed and cutleaf coneflower, tall blue lettuce leaves “vary considerably.” The ones lower on the stem have deep lobes:

tall blue lettuce lower leaves photo wildbluelettuceleaves_zpsxdl9cvih.jpg

Leaves higher up have a different shape:

tall blue lettuce top leaves photo wildbluelettucevertical.com_zpswxa7edgw.jpg

In mid-August, some tall blue lettuce plants were just starting to flower, with most buds still closed.

tall blue lettuce with buds photo wildbluelettucebuds_zpssv0rfsgv.jpg

Other plants had more flowers open around the same time:

tall blue lettuce blooming photo wildbluelettuce2_zpshb5jtuby.jpg

tall blue lettuce group photo wildbluelettucemanyflowers_zpsevokzgtp.jpg

Flowers are most often pale purple.

tall blue lettuce blooming photo wildbluelettucehorizontal1_zpsakmjgtdf.jpg

They can be almost white.

tall blue lettuce white photo wildbluelettucetopleaves_zpsm1m0fnsg.jpg

These flowers were a deeper color than most in my area:

tall blue lettuce deeper blue photo wildbluelettucehorizontal2_zpsu6vxbjjz.jpg

Tall blue lettuce can reach heights of twelve feet, but I’ve never seen plants that large. This plant was around seven feet tall, which is a more typical height.

tall blue lettuce large group photo wildbluelettucelargegroup_zpsc17y3afo.jpg

This was one of the shortest tall blue lettuce plants I found blooming. The small, darker blue flowers closer to the ground are dayflowers.

tall blue lettuce with dayflowers photo wildbluelettucedayflowers2_zpsta4ugi7a.jpg

Tall blue lettuce in the center, with American bellflower blooming near the lower left and some kind of goldenrod near the upper right:

tall blue lettuce with bellflowers photo wildbluelettucebellflowergoldenrod_zpsbevcla4k.jpg

The tall blue lettuce is out of focus, but you can see American bellflowers and a yellow jewelweed blooming here:

tall blue lettuce with jewelweed photo wildbluelettucejewelweed_zpshflldiot.jpg

Tall blue lettuce in the foreground; the plant with white flowerheads is some kind of boneset, possibly tall boneset. The yellow flowers in the background are brown-eyed Susan.

tall blue lettuce with boneset photo wildbluelettuceboneset_zpsnupbk895.jpg

Tall blue lettuce gone to seed in early October:

tall blue lettuce gone to seed photo wildbluelettuceseeds4_zpsjzz0lzgq.jpg

Tags: Wildflowers

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