Previous summer warmth gave no clear link to next spring lilac bloom in four US samples in 1965-2008

We tested whether warmth in the previous July and August was linked to next spring first bloom after current winter and spring controls. Four US region and period fits used 9,015 repeated lilac records in 1965-2008, with plant and year effects. Previous-summer slopes ranged from -0.082 to +0.639 days per C. All four intervals included zero after correction for four tests. Plant trends, curved current weather, flag exclusion, and a longer previous-summer window also gave uncertain slopes. This does not exclude a summer effect on flower formation or timing. Broad intervals, coarse weather, selected plants, unknown visits, different plant types by region, and few state clusters limit inference. The study does not measure pollution, community diversity, or causal climate-change effects. The package includes a raw-data rebuild, exact source hashes, derived panels, code, all estimates, numerical checks, and a figure.

phenology · lilac · previous summer · temperature · observation bias · regional replication · null result