Mechanism that causes plants to bloom when temperature rises identified

With parts of England enjoying a spectacular, but drought ridden spring, one asks what causes the timing of plants coming into bloom.

Flowering is activated by a special molecule, called Florigen. Florigen is activated by many signals, including the longer days of spring. Some plants rely more on temperature, others more on daylength to control key stages in their life cycle such as leaf emergence and flowering. This is reflected in the old saying "Ash before Oak, you're in for a soak; Oak before Ash, you're in for a splash."

With warm air, a control gene, called PIF4, activates the flowering pathway, but at lower temperatures the gene is unable to act.  

Hence climate change will lead to plants blooming earlier in the year.

http://www.physorg.com/news/2012-03-blooming-marvelous-climate-earlier.html