Nabalus altissimus (L.) Hook.

Rough White Lettuce, Rattlesnake Root

Nabalus altissimus plant

Family - Asteraceae

Stem - Erect, to 2 m, usually glabrous, often with purple coloration, sometimes glaucous.

Nabalus altissimus stemStem.

Leaves - Variable. Springtime emergent leaves often deeply lobed or with indistinct hastate lobes at bases. Lower cauline leaves petiolate, usually lobed, usually with a few broad, shallow teeth. Upper cauline leaves progressively smaller, with shorter petioles, less often lobed.

Nabalus altissimus leafEmergent leaves.

Nabalus altissimus leafLower stem leaf.

Nabalus altissimus leafUpper stem leaf.

Inflorescence - Typically broad panicles, with heads tending to cluster. Heads nodding.

Nabalus altissimus inflorescenceInflorescence.

Involucre - 9-14 mm long, cylindrical, with short outer bracts and 4-6 longer, pale greenish inner bracts.

Nabalus altissimus involucreInvolucre.

Flower - Ligulate florets 4-6, cream to yellow, with 5-6 mm orange-brown pappus.

Nabalus altissimus flowerFlower.

Fruit - 4-5 mm long, light brown or yellowish brown.

Flowering - July - October.

Habitat - Streambanks, mesic and bottomland forests, bluffs.

Origin - Native to North America.

Other info - This is the species of Nabalus most often encountered in Missouri. It is easily recognized by its open inflorescences and narrow heads with smooth involucres. It is most commonly found in moist areas with light to moderate shade. It seems to be a favorite of deer, which will often browse it preferentially over other vegetation.
The species was formerly known as Prenanthes altissima.

Photographs taken at Taum Sauk State Park, Iron County, MO, 9-27-2010, Young Conservation Area, Jefferson County, MO, 9-24-2014, Valley View Glade Natural Area, Jefferson County, MO, 9-28-2014, and Glassberg Conservation Area, Jefferson County, MO, 9-25-2015 (SRTurner).