Wednesday, September 11, 2013

Native Species Profile - White Lettuce

When most people think of woodland wildflowers they think of the spring ephemerals such as trilliums, trout lilies, and hepaticas.  Fall is rarely thought of as a season to find woodland wildflowers, but they can be found in certain habitats.  Probably the best place to search for fall woodland wildflowers is in floodplain forest, along wooded streams, the edges of swamps, and other habitats with moist soil.  Many of these species grow in open woodlands, where the forest floor does receive partial sun throughout the day.  Unlike spring wildflowers which tend to be low, rarely reaching over a foot in height, fall woodland wildflower species are often tall and showy.

Among the taller fall wildflowers is White Lettuce (Prenanthes alba).  White Lettuce commonly grows between 2 and 5 foot tall.  It grows in wet woodlands throughout northeastern North America. It is found as far west as the Dakotas and Saskatchewan and as far south as northwest Arkansas and western North Carolina.  Overall it is found in twenty-six states.  A separate species, Tall White Lettuce (Prenanthes altissima) is wider ranging, growing throughout the Northeast and as far south as the Gulf States.

White Lettuce is easy to identify from its leaves alone.  While the flower does not bloom in Mid-Michigan until August or September, the leaves can be found as early as mid-May.  The leaves grow alternately on the stem and can grow to 8 inches long and 6 inches wide.  Each leaf is deeply lobed with 3-5 lobes per leaf.  The largest leaves can be found closer to the bottom of the plant.  Leaves near the top of the stem become smaller and simpler and are often not lobed.

White Lettuce leaves - late May

White Lettuce leaves - late May

The plant branches near the top.  Each branch of the stem will produces several flowers clustered near the end of the branch.  The flowers of White Lettuce are bell shaped and drooping, hanging below the branching stems.  Each flower is approximately 3/4 of an inch long and 1/2 an inch wide.  Flowers are white with a purple tint.  The petals spread widely when the flower is in bloom allowing access to bumblebees. In Mid-Michigan the plant blooms from August through September.  Seeds produced by the plant resemble small dandelion seeds complete with a brownish-white parachute.  These seeds are readily spread by the wind.

White Lettuce flowers - not the branching stems, small leaves, and drooping blossoms

White Lettuce (Prenanthes alba) flowers

Close-up view of White Lettuce (Prenanthes alba) flowers

Another close-up of the White Lettuce flowers - not the widely spreading petals

White Lettuce is also known as White Rattlesnake-root, indicating that it may have been used in the past as a folk cure for snakebite. 

Sources seem to be mixed on the proper habitat for this plant.  Some authors list Wild Lettuce as a species of dry habitats including prairies, sand dunes, and dry open conifer and broadleaf forests.  Other authors list the plant growing in wet woodlands only.  The USDA lists the plant as being a Facultative Upland species - which is a fancy way of saying that it usually grows in dry habitats, but is sometimes found in wetlands.  I have typically found it growing only in moist woodlands and along the edges of swamps.

Basic Information

White Lettuce 
(White Rattlesnake-root) 
Prenanthes alba

Height:  2-5’ tall

Habitat:  wet woodlands

Flower Color:  white

Bloom Time:  August- September

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