Nabalus (Asteraceae) species of Central New York

by Arieh Tal, 2016

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Nabalus is a small genus of plants (ca. 18 spp.) found in North America and East Asia.  Three species are relatively common in Central New York:  N. albus, N. altissimus and N. trifoliolatus1Populations tend to be small and infrequent, found mostly in wooded habitats.  Of other genera in the flora of North America, Nabalus is probably most closely related to Lactuca (wild lettuces).

Vernacular names for this genus include rattlesnake root, lion's foot and white lettuce.

This genus had long been known by the scientific name Prenanthes.  However, recent phylogenetic research has determined that our species do not belong in the Eurasian genus PrenanthesKilian, et al. (2009)Bogler (2006)Haines (2011).

In general, Nabalus species are perennials, typically producing a single, erect stem from a taproot.  The sap is milky white.  Branching is usually alternate.  The overall inflorescence varies from extremely tall and narrow to quite wide and diffused.  Branch inflorescences consist of small, compact clusters of flower heads distributed along lateral branches or in stem leaf axilsFlower heads are borne on short peduncles, nodding/drooping (pendulous) when in flower, and small, each containing only from 4 to 14 floretsInvolucral bracts of our 3 common species are glabrous, various shades of green or pinkish-green, and occur in two series, an inner series of longer more/less equal-length bracts, and an outer series of much smaller bracts.

Leaf size and shape are quite variable across different populations, within populations and even on the same plant.  Leaf shape may be ovate, triangular or lanceolate; lobed, divided or "simple" (i.e., neither lobed nor divided).  The general pattern is for lower stem leaves to be larger, broader and more often lobed or divided than upper stem leaves.

Though our species of Nabalus are few in number, they are nevertheless rather difficult to distinguish, for they are morphologically similar and share many character states.  Leaves and stems are usually not diagnostic.  It is not possible to confidently identify immature plants from leaves alone.  The best way to identify these species is from examination of flowers and fruits.  Floret and involucral bract counts (per flower head), color of the pappus bristles and involucral bract surface characteristics are the most useful distinguishing characters.  For additional details visit the species pages at:  N. albus, N. altissimus, N. trifoliolatus.

Table 1 (below) summarizes the logic for identification.  N. serpentarius is also included in the following table for comparison in case new populations are found.

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1Only one collection of N. serpentarius is on record for the region (in Chemung Co., 1897).  It is not known if that population has persisted.

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