June Flowering Phenology

by Carl Strang

Already by this point in the season it is clear that first flowering dates are converging, the differences among years becoming smaller by the month. Nevertheless, this year’s median June difference from last year (among 69 species) was 14 days, a full 2 weeks later (the May difference was 24 days).

Staghorn sumac first opened flowers on June 14 at Mayslake Forest Preserve this year.

Staghorn sumac first opened flowers on June 14 at Mayslake Forest Preserve this year.

Musk thistle, less desirable in the landscape but beautiful nevertheless, first bloomed on the same day.

Musk thistle, less desirable in the landscape but beautiful nevertheless, first bloomed on the same day.

Last year was an anomaly, a hot dry spring following a mild winter. When this year’s first flower dates are compared to those for the previous 3 years, the differences are much less. Flowers appeared a median 1.5 days earlier than in 2011 (62 species), 5 days later than in 2010 (45 species), and 4 days earlier than in 2009 (50 species).

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