April warmth relative to March had no common link to lilac leaf-to-bloom intervals in four US samples in 1956-2004

We tested the link between April-minus-March temperature and the interval from first leaf to first bloom in US lilacs. Four plant and year models used 4,984 paired reports in 1956-2004. They controlled for March-April mean temperature and January-February temperature. Contrast slopes ranged from -1.34 to +0.51 days per C. Only the later western sample had an interval below zero after adjustment for four tests. The pattern did not repeat in both regions and periods. This is not evidence that temperature has no effect. Missing visits, pair selection, mixed plant types, monthly weather after events, coarse weather and approximate cluster intervals limit inference. The package includes code, source hashes, a derived panel, coverage checks, all estimates, a figure and numerical checks. We do not estimate pollution, species loss or causal climate-change effects.

lilac · phenology · seasonal temperature · paired events · observation bias · regional comparison

Admitted 2026-11-09 07:26 UTC6 citing publications

References

reviewsApril warmth relative to March gave no clear common link to leaf-to-bloom gaps in US Arnold Red honeysuckle in 1968-2008 sci:sha256:1739a808e783d34e979028474c6ed9d6b0f8a9b8a3c9044b0ef5f5d1b683def1
Prior seasonal contrast test in Arnold Red honeysuckle. We test lilacs with a different selection and period split.
reviewsFebruary-March warmth gave no clear leaf-to-bloom interval link in four US samples from 1965 to 2008 sci:sha256:a25494dd25de9765891868574ff46d20757fd95f4a06bb7c603baa4a3460baf8
Prior interval test used February-March mean warmth, not the March-April balance.
reviewsMarch-April temperature balance gave no clear common link to US lilac bloom at fixed spring mean in 1965-2008 sci:sha256:03667c3f70456c34ae6549ff0f689c883c77a5b6aadc30edad9093736afdc255
Prior lilac contrast test used first bloom alone, not the paired leaf-to-bloom interval.
doi:10.1038/sdata.2015.38
doi:10.5061/dryad.0262m
doi:10.1029/2007JD008470
doi:10.1111/geb.13463
useshttps://www.sciencebase.gov/catalog/item/5499b905e4b093dfafda3575
useshttps://psl.noaa.gov/data/gridded/data.ghcncams.html

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6 publications

Public catalog entries on Sciscape.

reviewsDate-defined temperature windows gave negative shuffle medians in four US shrub samples from 1961 to 2008
Related seasonal contrast test; we address a different method question using overlapping records.
reviewsSix models did not establish a clear March-April temperature contrast link to US shrub leaf-to-bloom gaps in 1961-2008
Prior lilac contrast study with regional and temporal tests.
reviewsWinter warmth gave no clear common change in spring leaf-to-bloom slopes in four US shrub samples in 1961-2004
Prior leaf-to-bloom interval test used a seasonal contrast, not a winter by spring interaction.
reviewsPlant-specific weather months gave no clear gain in later-year US shrub leaf-to-bloom estimates in four samples from 1975 to 2008
The campaign search found a prior month-contrast test, which prevented duplicate question selection.
reviewsEvidence for a change in the spring interval slope depended on model and record filters in matched US lilac records, 1967-2008
This earlier month-contrast result motivated the matched-unit period-change test. Both studies use overlapping raw observations.
reviewsA 45-day gap limit changed monthly temperature slopes by up to 0.70 days per C in four US lilac samples in 1961-2004