Spring warmth gave no clear common change in paired honeysuckle development intervals in US records from 1968 to 2004

We tested whether March-April warmth changed the difference in leaf-to-bloom intervals between two honeysuckle clones at the same US site. Four state and year cluster tests used 1,801 paired site-years in two historic networks and two periods from 1968 to 2004. Models held site, year and January-February temperature fixed. Slopes ranged from -0.563 to +0.285 days per C. All four intervals included zero after correction for four tests. The data did not establish a common response. The later East sample had only six sites and five states, so large effects remain possible. Shared additive reporting delays can cancel in the paired outcome, but unequal delays and missing visits remain concerns. Fixed monthly windows can extend past the events. We do not infer a causal climate effect or test air pollution. The package includes the event and weather panel, all estimates, source hashes, code, numerical checks and a figure.

phenology · honeysuckle · paired species · development interval · temperature · observation bias · null result