White rattlesnake root

Appearance

This herbaceous perennial wildflower is 0.60 to -1.5 meters tall; it has an erect central stem and often develops short side stems in the upper half.

The central stem is terete, light green to purple (usually the latter), glabrous, and glaucous. The alternate leaves are up to 20 cm long and 15 cm across (excluding the petioles), becoming gradually smaller as they ascend the stems.

The leaves are variable in shape; they are usually 3-5 lobed and less often deltate or ovate. The margins of these leaves are dentate, undulate, or smooth. The upper surface of each leaf is medium to dark green and glabrous.

The winged petioles are as long as their leaf blades or shorter. Both the stems and leaves contain a milky white latex. The central stem and upper stems (if any) terminate in panicles of flowerheads up to 60 cm long and 30 cm across. Each panicle has a central stalk that divides at its apex into 2-4 spreading branches; there may be some lower branches below. From each branch, several flowerheads droop downward from very short branchlets and peduncles. The light green to purple branches, branchlets, and peduncles of each panicle are glabrous.

Each flowerhead is about 1.9 cm long and 1.2 cm across. The cylindrical base of each flowerhead has 8 primary bracts (phyllaries) that are linear in shape, pale greenish purple to purple, and glabrous.

There are also several secondary bracts at the very bottom of the flowerhead that are much shorter than the primary bracts. The upper flowerhead has 8-14 outer ray florets and no disk florets; the petaloid rays of these florets spread outward widely when the flowerhead is in bloom. These petaloid rays are pale purple, lavender, or white; they are linear in shape with minutely toothed truncate tips.

The blooming period occurs from late summer into the fall. A pleasant floral fragrance is sometimes present. The florets are replaced by small oblongoid achenes with tufts of cinnamon-brown hair at their apices; the achenes are distributed by the wind. The root system is fleshy.

Naming

Prenanthes alba Linnaeus
Nabalus albus (Linnaeus) Hooker

Distribution

Man., Ont., Que., Sask.; Ark., Conn., Del., Ga., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Pa., R.I., S.Dak., Tenn., Vt., Va., W.Va., Wis.

Habitat

Sandy oak-scrub, open oak-hickory woods, deciduous forests, dunes, creek banks, road cuts.

Reproduction

The flowerheads are cross-pollinated by bumblebees, which seek nectar. Seeds are wind dispersed.

Predators

The following aphids have been observed on White Lettuce: Hyperomyzus nabali, Uroleucon ambrosiae, and Uroleucon chrysanthemi. Even though the foliage of this species has a bitter taste, it is sometimes browsed by White-Tailed Deer.