July Flowering Phenology

by Carl Strang

Before July, first flower dates had been running about 2 weeks early this year. Past experience led me to expect that the interval would drop as the summer progressed. So, what actually happened at Mayslake Forest Preserve?

Compared to last year, 37 species bloomed a median 10 days earlier in July, a week less than June’s difference. The range was 48 days earlier to 22 days later. The gap with 2010, which also had been a relatively early year, was down to a median 6.5 days earlier in July (vs. 8 for June), the range for 30 species was 32 days earlier to 28 days later. The difference was back up, to 12.5 days, in the comparison to 2009 (28 species, range 39 days earlier to 20 days later). That difference was 19 days in June.

Blue vervain was the most representative species in July, blooming 13 days earlier than last year, 10 days earlier than in 2010, and 13 days earlier than in 2009.

Naturally I expect the difference to drop still more in August.


1 Comment

  1. Sam Droege said,

    August 10, 2012 at 7:17 am


    Just wanted to say that I enjoy your posts and the insights that come from tracking phenology and natural history …. keep up the good work! sam

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