Purple milkweed results from 2009

I just finished entering all my 2009 field notes in an Excel file. I have been doing this every year for the past seven or eight years, and it has proved really useful. Among other things, it gives me a chance to review all the field notes and remind me of things that must be done in the 2010 field season. In addition, I am creating a database of all plant species present at Pleasant Valley Conservancy, including their locations and phenology.

An important part of the computerized data are those for purple milkweed (Asclepias purpurea), an endangered species that arose spontaneously at Pleasant Valley Conservancy after we initiated restoration. Because it is a "savanna" species of considerable importance, I have been carrying out field observations ever since the first population arose spontaneously in Unit 12B in 1999.

I published a summary of the purple milkweed work in the September 2009 issue of Ecological Restoration, which included all field and experimental work through the end of 2008. The analysis just completed adds an additional year of data.

With Kathie's important help, I have learned how to raise purple milkweed seedlings and transplant them successfully to the field. Most of these transplants have flourished, and some of them have flowered well. A few have even made seed pods, an important goal of the work and one more difficult to accomplish. (Pollination in milkweeds is notoriously complex, and pollinating insects are catch-as-catch can.)



The first year I found a purple milkweed pod was 2001, and some years afterward I found none. Perhaps because we are currently in a wet period in southern Wisconsin, pod formation has been better lately, and this year I found 50 pods, the most ever. Pods were about equally divided between those forming on spontaneous plants and those on transplants.

Interestingly, almost every year I find a new spontaneous population of purple milkweed, and this year I had an especially good one. When I do find such a population, I am never sure whether it has arrived completely on its own, or whether it is a place where I had thrown out seed some years ago.

The unpredicability of purple milkweed growth is maddening. Every one of my populations has a permanent numbered marker, and at some locations there will be years without any plant, followed by years where there is a flourishing plant. All, presumably, without the effects of any human agency.

I'll report on some other results from my 2009 database in later posts.