Thursday, April 11, 2013

Native Species Profile - Large-flowered Trillium

Despite this weekend's forecast of possible snow showers, Spring seems to finally be upon us.  Plants are starting to push up out of the ground in many places.  Within a few weeks our spring ephemerals will be putting on their annual show.  While many of the spring wildflowers are small and unassuming, there is one that is large and stands up demanding attention - the Large-flowered Trillium (Trillium grandiflorum).

Large-flowered Trillium - note the three petals and three leaves

Because of the large size of the plant (up to 18 inches tall) and flower (up to 5.5 inches across) the Large-flowered Trillium is one of the most recognized flowers throughout the eastern United States and Canada.  It can be found in deciduous forests as far south as Georgia and Alabama and north into Ontario and Quebec.

The simple structure of the plant and its flower also makes it easy to identify.  Each plant has three broad leaves that are arranged in whorled pattern around the stem and each Large-flowered Trillium plant is topped with one flower with three petals.  The petals are typically white, but fade to a soft pink as they age.  Bright yellow pollen covers the stamens at the center of the bloom.  While this plant may bloom any time between April and June in the northern United States and Canada, in Mid-Michigan the bloom usually peaks around the 3rd or 4th week of April into the 1st week of May. 

The arrangement of things in threes (leaves, petals, sepals) on the trillium has given the plant its name.  
Tri = three.  The illium come from the fact that the plant is in the Lily family (Lilium).  Add the two together and get Tri-lilium, a lily in three parts, which is then shortened to trillium. The grandiflorum in Trillium grandiflorum means "large flowered".  The Trillium grandiflorum has the largest flowers of the 38 species of trillium.

A hillside covered with Large-flowered Trillium

The Large-flowered Trillium is one of many spring wildflowers that is spread on a small scale by the activity of ants.  Ants collect the seeds from this plant and take them back to their burrows.  The seeds are covered with a fleshy coating that the ants eat, the seed is then discarded in the ants' midden (garbage) pile where it often germinates, growing into a new plant.  The pace of this small scale dispersion leads many scientists to question how the plant could have spread so far north since the end of the last glaciation.

An alternate theory of dispersion involves white-tailed deer.  Deer love trilliums, when they eat the fruit from the plant the seeds pass through their digestive system and are deposited in their dropping some distance from the parent plant.  This relationship can be a double edged sword.  As deer populations increase, over-grazing has eliminated trillium (and many other wildflower species) from many forests.

Sometimes you might find trillium that have petals that are partly (or wholly) green.  This is the result of an infection by a mycoplasma.  A mycoplasma is a form of bacteria that lacks a cell wall.  This infection will first be noted as a green stripe near the center of each petal.  As the infection spreads in successive years the stripe widens until the whole petal may be green.  This infection can also cause deformed petals or even double blooms (so each flower would have six instead of three petals).  This infection eventually impairs the reproductive ability of the infected plant and prevents successful seed production.

Large-flowerd Trillium infected by mycoplasma

Basic Information

Large-flowered Trillium 
Trillium grandiflorum

Height:  8-18” tall

Habitat:  deciduous woodland

Flower Color:  white, some flowers are turned green by a bacteria

Bloom Time:  April – June

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