Spring’s vernal wonders

SPRING in Ireland is not like spring anywhere else in the world. Because of our position out in the Atlantic at a latitude of over 50 degrees north it arrives late and in a rush.

Four key factors control its advance — air temperature, soil temperature, day length and soil moisture content.

The relationship between air temperature and soil temperature is quite complicated. In general soil temperature lags behind mean daily air temperature by three or four weeks in spring. However, the difference is not constant. What holds back the soil temperature is cold nights, often dropping to below zero. However, as spring progresses the nights rapidly get shorter, their influence wanes and the soil begins to catch up with the air.