First-to-full bloom gaps had uncertain warmth links in four US samples from 1965 to 2008

We tested whether spring warmth was linked to a shorter time from first bloom to full bloom. We used 15,153 paired lilac and honeysuckle records from US sites in 1965-2008. Four East/West and early/late models included plant and year effects. All four adjusted gap intervals included zero. Slopes ranged from -0.378 to +0.256 days per C of March-April warmth. A separate reporting test used 16,075 first-bloom records. In the West, full-bloom reporting fell by about 0.9 and 1.1 percentage points per C in the two periods. Both main adjusted intervals excluded zero. The later result became uncertain with plant trends, and April-only tests were uncertain in both periods. Missing reports cannot distinguish missed visits from failure to reach full bloom. Selected planted shrubs, different taxa, coarse weather, missing visits, and approximate cluster intervals limit inference. This is not a causal climate-change or pollution test. The package includes source hashes, code, a derived panel, all estimates, eight numerical checks, and two figures.

phenology · full bloom · observation bias · spring temperature · lilac · honeysuckle · regional replication · null result