April Flowering Phenology

by Carl Strang

April was a cooler, more seasonable month than March, which had remarkably early flowering dates for the early plants (recap: March had medians of 32 days earlier than in 2009, 21 days earlier than 2010, and 31.5 days earlier than last year). Since flowering is related to cumulative soil warming, I expected April to show a continuation of the early season, though not necessarily as dramatic. Such was indeed the case.

Ohio buckeye was the most representative plant in April, blooming 25 days earlier than in 2009, 13 days earlier than in 2010, and 30 days earlier than last year.

The plants that bloomed in April this year at Mayslake Forest Preserve were a median 24 days earlier than in 2009 (25 species, range 14 to 55 days earlier), 13 days earlier than in 2010 (25 species, range 3 to 47 days earlier), and 27 days earlier than last year (31 species, range 12 to 37 days earlier).

Wayfaring tree bloomed 31 days earlier than last year, when I first found the plant on the preserve.

I don’t find every plant every year, but the sample size is large enough to be representative.

Pussytoes wasn’t included in any comparisons this year, because I did not find it until this spring. There may be only one tiny colony on the entire preserve.

So, plants continue to bloom 2-4 weeks early this year. The difference should decline each month, as soil heat approaches its effective maximum while later-season plants come into play.


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