Prenanthes altissima Linnaeus

Remark The words or terms in red (actually dark orange) in the text are defined in a glossary.

sep_02_04.gthmb can't be loaded. Prenanthes altissima are perennial plants with erect stems that are from 40 cm to more than 2 m high, hence the epithet of the name. They grow from thickened, knotty, tuberous taproots. The plants are usually unbranched, except toward the apex where the flower heads occur. The species is native to North America. tuberous taproots. The chromosome number of the plant (2n) is 16.

The plant belongs to the Asteraceae family.


In Greek, πρηνησ (prênês) means nodding and ανθοσ (anthos) means flower, the genus name alluding to the drooping flower heads.

In Latin, altus means high, and altissimus is its superlative; the epithet refers then to the large height of Prenanthes altissima that can reach over 2 meters.

Common names

Some of the vernacular names of Prenanthes altissima are Tall Rattlesnakeroot, Rattlesnake Root, Tall White Lettuce and Lion's Foot. The French vernacular name is Prenanthe élevée.


Prenanthes altissima has also been known as:


Prenanthes altissima is recognized by: The other Prenanthes species found in Québec have a larger number of florets and phyllaries. As a general rule, leaf shape is unreliable as a guide to identification because it is highly variable within each species of Prenanthes. draw.jpg can't be loaded.




Flower heads

Halictid bees, beetles, and other insects may feed on the pollen, but they are not effective pollinators.



Habitats of Prenanthes altissima include rich mesic woodlands, rocky upland woodlands, sandy woodlands, bluffs and shaded ravines, woodland borders, swamps and seeps, and shaded to partially shaded riverbanks. The species is found in deciduous woodlands where Sugar Maple (Acer saccharum), American Basswood (Tilia americana), and American Beech (Fagus grandifolia) are often present as canopy trees.


map_na.jpg can't be loaded. Prenanthes altissima is found in the eastern half of Canada and the USA. The map shows the Canadian provinces and USA states where the plant can be found.


Even though it has a bitter taste, White-Tailed Deer occasionally browse on the foliage of Prenanthes altissima. The Iroquois used a poultice against dog and rattlesnake bites, hence one of the common name Rattlesnake root.


The photos of the gallery were taken either with one of the following: Minolta DiMAGE 7, Canon PowerShot A530, Canon Xt Rebel, usually with the EF-S60mm f/2.8 Macro USM objective, Fujifilm A 610 and EPSON Perfection 1650 (scanner). The title in the window shows the date when the picture was taken, i.e. jan_30_06... would mean that the photo was taken on the 30th of January, the 06 is for the 6th picture taken that day. The month, day and picture number might be followed by a letter which I use to identify the system used to take the picture.

Click on the thumbnails to get larger view. The original photos are usually in TIFF format, the photos shown are generally in JPEG format, often of dimensions one half (surface one quarter) for loading time reduction.


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sep_09_01s.mthmb cannot be loaded. The leaves were scanned at 300 dpi, and the dimensions of the resulting picture divided by 2 (area divided by 4); this allows to measure the dimensions of the leaves.

Flower heads

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