by Carl Strang


Part of the ongoing story of a place is its seasonality. Phenology focuses on the timing of seasonal events, comparing them between years and considering potential causal factors such as climate. Included are such things as first flowering dates for different plant species, arrivals of migrating birds, first frost, first snow, any kind of measurable definite event. I have featured some examples regarding birds in earlier posts. Today I want to look at plants.


April 10 this year marked the first wildflower I have observed at Mayslake Forest Preserve. It was a common blue violet, Viola sororia (here, as usual, I follow Swink and Wilhelm’s Plants of the Chicago Region, 4th edition).




In the same week, trout lily leaves rapidly expanded, and flowers won’t be far behind.




As this is my first year at Mayslake, at this point I am establishing a baseline for future years’ comparisons. This is an early date for a first flower of any kind, and in fact Swink and Wilhelm open the flowering date range for the common blue violet on April 15. On the other hand, this is just one plant, and I saw no others close to flowering. All of these considerations are examples of why some care is needed in interpretations. My own practice is to look at patterns in many species rather than focusing too much on any single one. More on that later, when I have more data.


  1. May 13, 2009 at 11:18 am

    […] all I am doing for now is establishing local first flowering dates in what will be an ongoing phenology  study. No doubt I will return to some of these species for other future inquiries. For instance, […]

  2. May 5, 2010 at 3:46 am

    […] year I started a study of flower phenology at Mayslake Forest Preserve. I recorded the date on which I saw the first open flowers of each […]

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