Monday, August 27, 2012

Prairie Dock

The Blue Jay Barrens population of Prairie Dock expands each year.  The large basal leaves make it impossible to overlook this species.

The original area of Prairie Dock was growing in almost permanent shade and was only about 30 feet across.  The Prairie Dock spread rapidly after I thinned out the trees to increase the light levels.  One to two dozen plants bloom each year.

Prairie Dock is generally unaffected by drought conditions.  Its roots go down many feet and can easily bring up enough water to keep the plant growing.  A problem occurs when bedrock stops the roots a foot or two beneath the surface.  On this site, a rainy year will definitely increase the number of flowering plants.

Shade also affects growth of the plants.  Prairie Dock was quick to spread into newly created partially shady areas.  It has failed to expand into the areas receiving full sun.  This is normally a plant of full sun and removing additional trees to create a more open habitat would seem the natural management scheme.  Since I can’t put the trees back once they are cut, I’ve been slowly thinning trees and evaluating the results.  Until I discover why the plants do not spread into the open areas, I’ll allow them to remain in the shade.

I do have a few plants that grow in full sun and thrive in that condition.  This mass of flowers was produced by some of the more robust plants on the property.

I maintain this cluster of plants in my garden.  The plants grew from seed produced in the previously described area.  Their purpose is to provide me with a source of Prairie Dock seed for reseeding projects.  Soil depth in this area is in excess of four feet and provides the plants with conditions much superior to those at the natural stand.

Several new plants have popped up in the vicinity of my garden plot.  Most are found in the fence row where birds have dropped the seeds.  Finches swarm to these plants and can clean up all of the seed in just a few days.  In order to harvest any seed for myself, I must cover the seed heads with netting to keep out the birds.

It may be the lack of competition that keeps the leaves on these garden plants shorter and smaller in size.  This is a three year old plant that is flowering for the first time.

For the most part, these flowers track the sun through the day.  The most spectacular view is in the early morning when the sun is still at a low angle.

Unlike many composite type flowers, the Prairie Dock flower does not produce seeds across the entire seed head.  The tubular flowers in the center of the disk are incapable of producing seed and serve only to produce pollen.  Seeds are produced by the ray flowers located at the base of the yellow petals.  In the photo, the candlestick shaped flowers are the pollen producers and the brown curls indicate the location of the seed makers.  The brown curl is the stigma that receives the pollen.  Newly produced stigmas are yellow-green in color and turn brown after pollination.

Peeling away the phyllaries exposes the ovary in which the seed will develop.  The mature fruit is known as an achene.

Here is an individual ray flower with attached ovary.

The achenes mature rapidly.  These will soon be attracting the finches.  The birds are often able to extract all of the achenes without disturbing the rest of the seed head.  It can be quite disappointing to begin seed collection only to find the birds have already cleaned everything out.

Most petals showed signs of being fed upon, but I saw very few insects.  I found another Spotted Cucumber Beetle, this one yellow.  It was sharing the flower with a small Crab Spider. 

The most interesting plant eater was this Stinging Rose Caterpillar working away at one of the big Prairie Dock leaves.


  1. That stinging rose caterpillar is unbelievable. Stunning!

    I also like your photos of the Prairie Dock anatomy. The Composite plant family is so interesting.

  2. Hi Gabrielle. I've seen several of the caterpillars this year. At each sighting, my first thought is of Clowns.

  3. Clowns with a sting!

    Prairie dock is one of my favorite prairie/savanna plants, and as your pictures demonstrate, a stunning landscape plant, too.

  4. Hi James. Clowns with a sting, indeed. But I've always been a little bit wary of clowns.

  5. An interesting and lovely plant. The caterpillar is incredible.

  6. Hi Pat. The caterpillar is one of my favorites. It can deliver a rather nasty sting, so its touch is to be avoided.

  7. I live in Erie, PA and grow Prairie Dock in my yard. I don't think my neighbors like it much but I've got a lot of Silphiums like Compass and Cup Plants too.

  8. Hi, Apeoj. It sounds like you have an interesting yard. When I lived in town, I found the neighbors quick to object to anything straying from the accepted norm. Now I have no nearby neighbors, so there is no problem.