Sunday, February 27, 2011

A Rare Thistle in the Sand

Despite the name of the blog being The Natural Treasures of 'Ohio', I'd like to escape our borders every once in a while for an out of state botanical adventure or two.  As unique and beautiful as Ohio is I think it's important to be well rounded and explore the infinite other areas of interest in our area of the country and beyond. 

Leelanau County, Michigan has been my summer vacation spot literally all my life.  A week or two each summer would be spent fishing the lakes for bass and pike, the cold, spring fed streams for trout, swimming in the chilly waters of Lake Michigan searching for petosky stones and soaking in the sun and beauty of northern Michigan.  I'll always cherish my time up there with my parents and brother and look forward to those days renewed when I may take my future family up there to experience the same magic.  My footprints in the sand along the beach may be quick to wash away but all the memories made are etched in stone in my brain.

As my interest and passion in the botanical world has increased the past few years so has my realization of just how incredibly diverse and unique this area is.  Recently I've been going through some pictures from a couple summers ago when I hiked and camped South Manitou Island.  I plan on doing a post about my experiences on the island and the interesting history and flora that come with it in the near future but I decided to do a quick appetizer of a post on an interesting plant I just now noticed in my picture archives.  I'm not quite sure what got me to photograph this plant three years ago, as I didn't know what it was and it really doesn't stand out in any way but I am very thankful I did.  Little did I know I was photographing and admiring the rare and federally, yes that's right, federally threatened Pitcher's Thistle (Cirsium pitcheri).

Typical habitat for the federally threatened Pitcher's Thistle
Also known as Dune Thistle, C. pitcheri can only be found growing along the shores and dunes of the Great Lakes in Michigan, Indiana, Illinois and Wisconsin.  There are also a few small populations in the Canadian province of Ontario.  Pitcher's Thistle occurs in its greatest numbers in Michigan where it is most common in the Sleeping Bear Dunes National Lakeshore, which includes South Manitou Island.   Growing only on open, windblown dunes and low beach ridges is what attributes to this plants rarity.  Already limited by it's naturally small amount of available habitat, shoreline development has played a large role in putting this species on the federal list of threatened and endangered plants.  Plant species that are obligated to shoreline and coastal habitats are among the most imperiled and endangered we have.  When society wants to develop every square inch of shoreline with summer homes, resorts, marinas and public beaches you lose the natural splendor and beauty to the predictable and cookie-cutter sights of concrete and asphalt.  The above picture shows the perched sand dunes on the western edge of the island that this plant calls home.  Commonly found growing alongside the thistle is Harebell (Campanula rotundifolia), a state threatened species in Ohio, and Hairy Puccoon (Lithospermum caroliniense) which both share the same desert-like habitat.

Flowering head of a Pitcher's Thistle
Pitcher's Thistle is a relatively easy member of the Cirsium genus to identify, which can't be said for many of the other species.  Each plant spends 2-8 years maturing as a rosette of blue-green leaves densely covered in wooly, white hairs.  Upon maturation each plant suddenly sends up a single stem with many prickly branches 3-4 feet high to flower.  A taproot up to 6 feet in depth certainly helps this plant growing in some of the most xeric conditions survive even the driest and toughest of times.  

Pitcher's Thistle plant
 Each flowering head is pale cream to rosy pink in color and blooms from June to September before setting to seed and being dispersed by the wind like all other thistle species.  An interesting thing about this plant is the fact it is monocarpic.  Monocarpic means a plant that only flowers and sets seeds once in its lifetime.  So after up to 8 years of patient growing and biding it's time, the Pitcher's Thistle gets only one chance to show off its beauty, be pollinated by an assortment of insects, seed and then die, leaving the future of its race up to the hundreds of seeds dancing in the summer breeze.  Large seed counts and high germination rates are important with species that are monocarpic and this plant is no exception.  Pitcher's Thistle got it's name from the first person to discover it and submit it to science.  Dr. Zina Pitcher was an army surgeon at Fort Brady in Sault Ste. Marie in the 1820's and found this plant growing in what is now the Grand Sable Dunes of Lake Superior.  An accomplished botanist, he stumbled across a flowering plant of C. pitcheri on a camping trip and didn't recognize it as a species he knew so sent it in for examination and the rest, as they say, is history.

As mentioned before I plan on publishing an in-depth post on the rest of South Manitou Island in the coming days.  Visible shipwrecks, virgin White Cedar (Thuja occidentalis) forests, rare and interesting flora and amazing vista views across Lake Michigan await the patient reader.  Until next time!

1 comment:

  1. Have you seen the Cirsium carolinianum at The Edge? It's one of our rare thistles, only grows at a few sites.