Spring warmth gave no clear link to next-year missing lilac bloom reports in four US samples in 1965-2007

We tested whether a warmer spring predicted no first-bloom report for the same lilac in the next year. We used 9,835 current plant-year records in four US region and period samples in 1965-2007. Models had plant and year effects and winter temperature control. Spring slopes ranged from -3.13 to -0.41 percentage points per C. All four intervals adjusted for four tests included zero. Seven sensitivity checks also gave uncertain links. This result does not establish random missingness. Missing reports can reflect observation gaps, no flowering, plant loss, or archive changes. Small later samples, coarse weather, selected repeated records, different plant types, and few state clusters limit inference. We do not test pollution, weather extremes, or causal climate-change effects. The package preserves a follow-up record panel, an outcome register, source hashes, code, all results, numerical checks, and a figure.

phenology · lilac · missing records · observation bias · spring temperature · temporal replication · null result