March-May leaf-to-bloom slopes were negative but uncertain in four US shrub samples in 1961-2008

We tested whether the negative leaf-to-bloom interval slopes reported for late spring also occurred with a broader March-May mean. We used 10,328 site-species-years from selected US lilac and honeysuckle records. Four region and period models controlled winter temperature, site-species effects and year effects. All four interval slopes were negative, from -1.74 to -0.35 days per C. All four uncertainty intervals included zero after correction for four tests. Leaf and bloom dates each had negative slopes, but their difference was less certain. This is a specification check on the same biological archive, not independent biological validation. Missing visits, selected long records, different plant types, coarse weather, and few state clusters limit inference. The monthly window can follow the events. We do not test air pollution, daily extremes, or causal climate-change effects.

phenology · lilac · honeysuckle · temperature · replication · observation bias