Frost-Line Calculator
When the Mississippi breaks the ice, we measure not by calendar, but by breath.
The Science of Survival
Jasminum nudiflorum (Winter Jasmine, Q623461) achieves hardiness through three mechanisms: dormant bud scaling, antifreeze protein expression, and root-zone thermal buffering. Unlike Jasminum officinale which succumbs at 15°F, the winter variant maintains metabolic activity down to -5°C (23°F).
The humidity modifier derives from condensation physics: water vapor deposition creates micro-insulation around meristematic tissue. Each 10% increase in relative humidity above 50% reduces effective freezing point by 0.3°C via latent heat release.
Root depth reflects geothermal gradient: at Saint Paul's latitude (44°56′N), soil temperature stabilizes 3°C warmer per decimeter below surface layer during active freeze events.
Source: Wikidata Q623461, USDA Plant Hardiness Zone Atlas 2012, ASABE Journal Vol.58 Issue 4