Tuesday, July 27, 2010

Wet Weather Prairie Growth

I headed out with the idea that I was going to walk through the winter mowed fields to check on their growth rates. Then I decided to look for the Blue Grosbeaks and their recently vacated nest. No signs of any nest in what I thought was a likely spot, so I wandered off in the direction the birds had taken to see if I might locate them in another field. Birds displaying blue coloration were not to be found, except for the Blue Jays of course, but I did find a nice bluish flower. The Scaly Blazing Star, Liatris squarrosa, seem to have synchronized their bloom period this year and are all flowering at once.

This is probably my favorite of the many Blazing Stars. The blooms on squarrosa are spaced far enough apart to allow appreciation of each individual component of the flower heads. I especially like the stiffly pointed bracts that surround the base of the flower head. The whole arrangement looks like a tiny bouquet wrapped in fancy paper.

The plant is rather short and can get hidden by even moderately tall grasses. You can be almost on top of them before you notice the splashes of violet among the grass leaves.

The prairie grasses, adapted to surviving extremely dry conditions, are taking full advantage of the frequent rains. Areas that normally show patches of bare ground are now completely covered by grass.

It’s the Big Bluestem that’s taking over the slopes this year. The density of Big Bluestem in the stand has been increasing steadily over the last 20 years. In a dry year these dry hillsides can grow Big Bluestem that reaches ten feet tall. I’m wondering what kind of height they’ll reach this year.

Years like this really help to boost the organic matter content of the soil. The decaying grass leaves will invigorate the soil biota and the soil will show a slight improvement. I’ve noticed that many prairie wildflowers show increased vigor in the second year following a rainy season. I’m guessing that’s the point at which the nutrients from the decomposing grass become most available.

The flowers are working to keep up with the grass. This Western Sunflower, Helianthus occidentalis, maintains most of its leaves near the ground, but the flower stalk may reach six feet into the air. These plants took advantage of plentiful sunlight before the grasses started to grow. They’ve just reached the stage where they are beginning to produce the flower stalk.

I found this Monarch caterpillar feeding on a Green Milkweed, Asclepias viridiflora. This milkweed species is smaller and has much less leaf mass than the Common Milkweed. Some of the plants could easily have their leaves stripped by a hungry caterpillar. This particular plant didn’t show any signs of feeding activity other than this one leaf. It’s possible that the caterpillar moved to this plant after stripping the leaves from another nearby milkweed. Leaving one plant to find another can be a risky venture. I wonder if the caterpillars have some way of sensing the best direction to go in search of a new food source.


  1. Interesting to see the difference in growth strategy between the Breccia and the Praire areas. I guess many of the spores and seeds will lie dormant until there is sufficient nutrients and of course rain water.

  2. You're right, Frank. There's also a big difference between individuals of the same species growing in different areas. Sometimes it's hard to tell that the little dwarfs growing on the really poor soil are the same species as the robust plants in the good soil.

  3. Hi Steve,

    Great images once again, especially that caterpillar. Wow, this brings back memories of the critters we caught when we were kids, then held captive in a mayonnaise jar with holes in the lid. It's a good thing we didn't get them all so some survive today!

    I'm glad to be on line today with a broadband connection. I'm not able to get your page to load via satellite throughout the rest of the week. I'm catching up on Sundays!