white rattlesnake root

(Nabalus albus)

               
Conservation Status

IUCN Red List

not yet assessed

white rattlesnake root

NatureServe

N5? - Secure

SNR - Unranked

Minnesota

not listed

Wetland
Indicator
Status

Great Plains

FACU - Facultative upland

Midwest

FACU - Facultative upland

Northcentral & Northeast

FACU - Facultative upland

Nativity

Native

 
Occurrence

Common

 
Habitat

Dry. Woods, deciduous forests. Partial sun or light shade.

 
Flowering

August to September

     
Flower Color

White to pale pink or lavender

     
Height

16 to 67

     

Identification

This is a 16 to 67 tall, erect, perennial forb that rises on usually a single stem from a taproot.

The stems are stout, erect, and sometimes branched near the top. They are light green and often mottled with purple, sometimes almost completely purple. They are hairless toward the base and inconspicuously, slightly hairy toward the tip with short, soft, curled hairs. They are often somewhat covered with a whitish, waxy bloom (glaucous).

Basal and lower stem leaves leaves are highly variable in shape. Each basal leaf is on leaf stalk (petiole) up to 7 long. The petiole is hairy and often purple. It is not winged. The leaf blade is usually triangular-shaped, 1½ to 11¾ long, and 1¼ to 7 wide. It is sometimes arrow-shaped, with a pair of outward-turned basal lobes. It is sometimes deeply cut into three lobes, sometimes divided into three leaflets. The upper surface is hairless. The lower surface is sparsely covered with short, curled hairs, and is often somewhat glaucous. The margin has a few outward-pointed teeth. Basal leaves are present at flowering time.

Stem leaves are alternate. Lower stem leaves are on narrowly-winged petioles up to 7 long. The petiole is shorter than or equal in length to the leaf blade. There is no large, leaf-like appendage (stipule) at the base of the petiole. The leaf blade is 1½ to 11¾ long, 1¼ to 7 wide, and highly variable in shape. It may be triangular, arrow-shaped, divided into 3 or 5 lobes, or egg-shaped. Leaves become progressively smaller, less divided, and on shorter petioles as they ascend the stem. The uppermost leaves may be stalkless, undivided, and untoothed. The upper surface is hairless. The lower surface is sparsely covered with short, curled hairs, and is often somewhat glaucous. When torn, the leaves exude a milky latex.

The inflorescence is a branched array (panicle) at the end of the stem and branches. The panicle has 2 to 4 long branches, each with a drooping cluster of 3 to 8 flower heads. The flower heads are clustered at the branch tip.

Each flower head is about ¾ long and ½ wide. At the base of the flower head is an involucre composed of an inner and an outer series of leaf-like appendages (bracts). The involucre is cylinder-shaped to bell-shaped, ½ to long, and to 3 16 wide. There are 6 to 9, usually 8, inner bracts. The inner bracts are purplish or maroon, narrowly oblong lance-shaped, ¼ to long, and hairless. They are somewhat curved inward at the tip. The outer surface is whitish in appearance due to a dense covering of minute, nipple-like projections (papillae). Individual papillae can be distinguished with a 10-power hand lens. The papillae are white and appear to be covered with a waxy coating. The outer series of involucral bracts is much shorter than the inner series. There are 5 to 7 outer bracts. They are green, sometimes tinged with purple or maroon, triangular-shaped, and hairless.

There are 7 to 13, usually no more than 9, ray florets and no disk florets. The ray florets are white, sometimes tinged with pink, lavender or red near the base, and to long.

The fruit is a brown or tan, to ¼ long achene (cypsela) with a tuft of feather-like hairs (pappus) attached to one end. The pappus is usually reddish-brown.

 
Similar
Species

Purple rattlesnake root (Nabalus racemosus) involucre bracts are hairy.

White-flowered leaf-cup (Polymnia canadensis) leaves are similar, but the petioles are not winged. The larger leaves have a large, rounded stipule at the base of the petiole that surrounds the stem. The lowest pair of lobes on pinnately-divided leaves is much reduced and is separated from the adjacent pair of lobes by a short section of winged leaf stalk.


Distribution Distribution Map   Sources: 2, 3, 4, 5, 7, 28.

Comments

 


Taxonomy

Family:

Asteraceae (aster)

 

Subfamily:

Cichorioideae

 

Tribe:

Cichorieae (lettuce)

 

Subtribe:

Hypochaeridinae

 
Synonyms

Prenanthes alba

Prenanthes alba var. alba

Prenanthes alba var. pallida

 
Common
Names

rattlesnake-root

white-lettuce

white rattlesnake root

white rattlesnakeroot

white rattlesnake-root


 

 

 

 

 

 

 

Glossary

achene

A dry, one-chambered, single-seeded fruit, formed from a single carpel, with the seed attached to the membranous outer layer (wall) only by the seed stalk; the wall, formed entirely from the wall of the superior ovary, does not split open at maturity, but relies on decay or predation to release the contents.

 

bract

Modified leaf at the base of a flower stalk or flower cluster.

 

cypsela

A dry, one-chambered, single-seeded fruit, formed from a single carpel, with the seed attached to the membranous outer layer (wall) only by the seed stalk; the wall, formed from the wall of the inferior ovary and also from other tissues derived from the receptacle or hypanthium, does not split open at maturity, but relies on decay or predation to release the contents.

 

glaucous

Pale green or bluish gray due to a whitish, powdery or waxy film, as on a plum or a grape.

 

involucre

A whorl of bracts beneath or surrounding a flower or flower cluster.

 

panicle

A pyramidal inflorescence with a main stem and branches. Flowers on the lower, longer branches mature earlier than those on the shorter, upper ones.

 

papilla

A tiny, rounded, nipple-like projection on the surface of a leaf or petal.

 

pappus

The modified calyx composed of awns, scales, bristles, or feather-like hairs in plants of the Aster family.

 

petiole

The stalk of a leaf blade or compound leaf that attaches the leaf blade to the stem.

 

stipule

A small, leaf-like, scale-like, glandular, or rarely spiny appendage found at the base of a leaf stalk, usually occurring in pairs and usually dropping soon.

 

winged leaf stalk

A leaf stalk with a leaf-like or membrane-like extension along both sides.

       

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Plant

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  white rattlesnake root    
       

Inflorescence

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  white rattlesnake root    
       

Flowers

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Buds

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Basal Leaves

  white rattlesnake root   white rattlesnake root
       
  white rattlesnake root   white rattlesnake root
       

Lower Stem Leaves

  white rattlesnake root   white rattlesnake root
       

Upper Stem Leaves

  white rattlesnake root   white rattlesnake root
       

Stem

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  Prenanthes alba (White Lettuce)  

 

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