March Flowering Phenology

by Carl Strang

This was by far the warmest March on record in northeast Illinois. As a result, I have enough phenology data to begin posting results a month ahead of my usual start. Today I will focus on first flower dates at Mayslake Forest Preserve.

The first white trout lily flowered on March 21. That was 22 days earlier than last year, 15 days earlier than in 2010, and 26 days earlier than in 2009.

My records only go back to 2009, but this year’s early dates were impressive nevertheless. Compared to last year, first flowering dates for the 20 species that bloomed in March ranged from 4 days later to 63 days earlier, with a median of 31.5 days earlier. A month early!

Wood anemone bloomed 17, 20 and 39 days earlier than in 2011, 2010 and 2009 respectively.

Factors other than seasonal warmth come into play when considering first flower dates on a particular site. The wood anemone in the previous photo is a case in point. At Mayslake that species grows only in a part of the savanna that had been thick with buckthorn and honeysuckle brush until the winter of 2008-9. The brush was cleared that winter, and part of that year’s much later blooming probably can be attributed to recovery from several years’ suppression by the shady brush.

Small-flowered buttercup bloomed 43, 15 and 37 days earlier than in 2011, 2010 and 2009 respectively.

Another factor to consider is human error. Small-flowered buttercup occurs as widely scattered individuals and thus is not very common at Mayslake. The flowers are relatively small, so I don’t spot them unless I am right on top of the plant. Data for this species therefore are a little less reliable than for more conspicuous and common ones like the trout lily at the top.

Compared to 2010, first flower dates in 2012 so far (21 species) ranged from 1 to 79 days earlier, with a median of 21 days earlier. Compared to 2009, first flower dates in 2012 so far (16 species; I do not have dates for all species each year) ranged from 15 to 60 days earlier, with a median of 32 days earlier.

It will be interesting to see how well this early phenology holds in the coming months.

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