Growth of Pitcher’s Thistle on the Flower Creek Dunes

Cirsium pitcheri, or Pitcher’s thistle, is a plant species found on the sand dunes surrounding the Great Lakes. Its current conservation status is classified as “threatened,” or vulnerable to endangerment. Due to being classified as such, plant numbers are monitored to determine whether their population is increasing, decreasing, or stable as well as to chart their growth. As part of a long-term project to study their numbers, data was collected August, 2016 at Flower Creek Dunes in Muskegon, Michigan. Two methods were used in collecting data on Pitcher’s thistle populations at this site. The southern side of Flower Creek Dunes was surveyed and a census of the thistles was taken. The northern dune was divided into six large quadrats created using strings, and from each section, six plants were randomly selected and data on them was recorded. For both methods, data was collected on the plants’ height, longest leaf length, length of major and minor axes, whether the plant was living or deceased, and number of flowers. The new 2016 data was combined with data gathered in 2014 and 2015. Statistical analyses of the data showed that the proportion of smaller thistles on the northern dune is not significantly different from that of the southern dune. It was also determined that the average longest leaf length increased between 2015 and 2016. Further studies will illumine the long-term growth and survival of Pitcher’s thistle at Flower Creek Dunes and may instigate studies at other locations along the Great Lakes