Spring warmth slopes for early-to-mid green-up included zero in four eastern US camera samples in 2008-2023

We tested whether warm springs shorten early-to-mid canopy green-up in 200 camera-years from 30 eastern US cameras in 2008-2023. Separate models for two regions and two periods controlled camera effects, year effects and winter temperature. All four estimated March-May temperature slopes were negative, from -1.951 to -0.515 days per C, but all ordinary and four-test confidence intervals included zero. All fitted precision, coverage, trend and threshold checks also included zero. Conditional ranges from source date intervals permitted either slope sign in every primary sample. These data do not establish a repeated shortening or its absence. The early southern sample has only three spatial clusters. Selected views, coarse weather, date error and missing seasons limit inference. No causal climate effect, pollution effect or biodiversity loss was tested. Code, aggregate evidence, source hashes and external retrieval instructions are included.