May Phenology

by Carl Strang

It’s time to update my record of flowering phenology at Mayslake Forest Preserve. Through April, plants were blooming a median of 13 days earlier than in 2009. In May I have an additional 41 species to report. Five of these were new to the list, and so I have no 2009 dates for comparison. These include nannyberry, about which I reported earlier. Other new shrubs are black raspberry, and autumn olive (shown).

I am not sure how I missed a prominent trailside patch of common speedwell last year.

Even more intriguing is this one:

Clearly a member of genus Senecio, this single plant keyed to butterweed. It is blooming close to the center of the preserve, so I am not sure how it got there. Butterweed is not native, and apparently is not commonly encountered in northeast Illinois, though DuPage Forest Preserve District botanist Scott Kobal tells me he has found it much more frequently in recent years.

Returning to the species for which I had flowering dates in 2009, I had to divide them into two groups. I was out of town for significant portions of May, and so found 16 species blooming profusely that had begun in my absences. The dates I was able to record for them certainly were later than their actual first flower dates must have been. The median was 3 days earlier than in 2009, range 15 days earlier to 5 days later.

Of more interest were the 20 species for which my 2010 first flower dates were reasonably close to the actual. There the range was 4-23 days earlier, with a median of 13. At least so far, 2010 flower phenology continues to be significantly ahead of 2009.

Curiously, migrant bird arrivals do not show the same pattern. The 15 species whose May arrival dates I can compare reasonably between years all appeared later in 2010 than in 2009. The range was 3-15 days later, with a median of 8 days. No explanation immediately comes to mind.



  1. George Kish said,

    June 10, 2010 at 12:23 pm

    I am very interested in your phenology observations. Have you considered registering your datasets with the USA-National Phenology Network ( As you may know, the USA-National Phenology Network is a consortium of federal and state agencies, universities, and non-profit groups studying the relation between the timing of biological events and climate changes.

    • natureinquiries said,

      June 11, 2010 at 5:58 am

      Thanks, George. I’ll check it out. If data entry takes much time, I may have to wait until a less hectic season to catch up.

      • George Kish said,

        June 11, 2010 at 8:26 am

        If you already have data in a spreadsheet, the National Coordinating office of the USA-NPN can assist you with entering your data sets in a secure location on the USA-NPN server. If you have your data in field books, an intern working with me can help you to get your data into a digital form. One of the functions of the USA-NPN is to encourage phenology observers like yourself to add your voice to a national network so we can all try to learn how climate affects biological events.

  2. June 10, 2010 at 7:10 pm

    Hi Carl. I agree with Scott Kobal… Senecio glabellus has increased dramatically in hte past few years. I monitor mitigation sites in northern Indiana regularly. This year, I saw this weed at every single one of my sites, including sites where I had not previously seen it. It is considered a native species in southern Indiana and further south, where it is a species of floodplains. In some places south of Indianapolis, it turns agricultural fields a glowing yellow in the spring. Watch for it to continue to increase up here.

    • natureinquiries said,

      June 11, 2010 at 5:57 am

      Interesting. Thanks, Scott.

  3. June 17, 2010 at 1:10 pm

    […] can pursue. I have been sharing my phenology observations at Mayslake Forest Preserve for first flowers, first fruits, and spring arrivals of migrant birds. Today I would like to look at results […]

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