April Flower Phenology

by Carl Strang

We finally got some flowers in April, so it is possible to quantify how late this spring has been compared to recent years. It should be no surprise that this is the latest spring of the last 5, at least as measured by first flower dates at Mayslake Forest Preserve. It also should be no surprise that the biggest contrast is between this year and last. For the 13 species of plants I could compare, the median difference was more than a month, with 2013’s median 34 days later than that for 2012.

Bloodroot hit the median exactly, blooming 34 days later this year than last.

Bloodroot hit the median exactly, blooming 34 days later this year than last.

The smallest difference was between 2013 and 2011 (the year of the Snowmageddon blizzard). Twelve species bloomed a median 4.5 days later this year.

Common blue violets flowered 4 days later this year than in 2011.

Common blue violets flowered 4 days later this year than in 2011.

Looking back at 2010, the difference is another big one, at 17 days (11 species).

Trout lilies hit the median, 17 days later in 2013 than in 2010.

Trout lilies hit the median, 17 days later in 2013 than in 2010.

Finally we go back to 2009, my first spring at Mayslake. It seems we have alternated early and late years, as the difference again is smaller. Nine species of plants bloomed a median 5 days later in 2013 than in 2009.

The representative example in this comparison is cutleaf toothwort, right on the 5-day median difference.

The representative example in this comparison is cutleaf toothwort, right on the 5-day median difference.

If 2013 runs true to form, there will be a gradual convergence of dates as the spring and summer progress.

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