February-March warmth gave no clear bloom-gap link in four US lilac and honeysuckle samples in 1968-2008

We tested whether February-March warmth changed the first-bloom date of lilac relative to Arnold Red honeysuckle at the same US site. Four models used 1,609 paired site-years in two historic networks and two periods from 1968 to 2008. Site and year effects and prior December-January temperature were held fixed. Slopes ranged from -0.08 to +0.55 days per degree Celsius. All four intervals included zero with correction for four tests. Sensitivity checks did not establish a common link. This result does not establish a zero response. The East sample used cloned lilac and the West sample used common lilac, so plant type and region cannot be separated. Sparse eastern coverage, unknown visit schedules, selected pairs, and coarse monthly weather limit inference. The test does not measure flowering overlap, biodiversity loss, air pollution effects, or a causal climate-change effect. The package includes source hashes, selected records, weather extracts, all models, figures, code, and reproduction instructions.

phenology · lilac · honeysuckle · temperature · observation bias · paired records · null result