Tom's Blog

Friday, November 13, 2015

Common milkweed (Asclepias syriaca) flourishes in oak savannas

The new Monarch butterfly initiative of the NRCS is focusing extensively on milkweeds.

Monarchs lay their eggs on milkweeds, where their caterpillars grow and pupate. Three species of milkweeds seem to be of prime importance in our area: Asclepias syriaca (common), A. incarnata (swamp), and A. tuberosa (butterfly). Because common milkweed is so easy to grow, and has a wide range of habitats, most of the work is on this species.

At Pleasant Valley Conservancy we have lots of milkweeds (seven species, to be exact). Not surprisingly, common is the most common! However. Although it does grow in our prairies, it really flourishes in several of our oak savannas. Who knew that this prairie plant "prefers" savannas?

The photo here was taken looking west on what we call the Mid Savanna Trail. In the distance (red arrow) Kathie can be (barely) seen immersed in about 1 acre of milkweed plants. (Since common milkweed is rhizomatous, it is not surprising that it spreads well. Check this link for an interesting example of how common milkweed rhizomes work. )

Red arrow; Kathie collecting milkweed pods along the Mid Savanna Trail
For the past two years Kathie has gone "all out" to collect common milkweed pods for a Monarch initiative at Madison Audubon Society's Goose Pond Sanctuary. In 2014 she collected over 4000 pods and in 2015 over 1000. Since each pod has more than 100 seeds, this gives some idea of how many seeds she has collected. The seeds from these pods are removed and cleaned by MAS volunteers, and the seeds then get distributed to new prairie sites at GP.

The site shown in the photo is one of our outstanding oak savanna habitats and one of my favorite sites. We usually stop here on our field trips for a lengthy discussion of how oak savanna restoration activities work. This location is easily reached from the trailhead by crossing the Pocket Prairie and walking uphill to the trail junction. Here you are in the midst of venerable open-grown white oaks that have been here at least since the 1850s.

Among other things, colleagues of entomologist Prof. David Hogg have been using this same site as a convenient location for collecting eggs for their Monarch cultivation project.


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