These lovely snowdrops popped up in my southwestern Ontario garden (zone 6b) in February, 2016.

Ever wonder how plants know when to start growing again in the spring? We know that temperature and light have something to do with it. Well, scientists led by the University of Cambridge have discovered the real mechanics behind what stimulates plant growth: a ‘thermometer’ molecule. Science Daily reported October, 2016, that:

” Researchers have revealed that molecules called phytochromes — used by plants to detect light during the day — actually change their function in darkness to become cellular temperature gauges that measure the heat of the night.

At night, these molecules change states, and the pace at which they change is “directly proportional to temperature” say scientists, who compare phytochromes to mercury in a thermometer. The warmer it is, the faster the molecular change — stimulating plant growth.”

So now you have the science behind the old British spring-predicting rhyme:

Oak before Ash, we’ll have a splash,

Ash before Oak, we’re in for a soak.

Lead researcher Dr. Philip Wigge of Cambridge’s Sainsbury Laboratory explained “Oak trees rely much more on temperature, likely using phytochromes as thermometers to dictate development, whereas Ash trees rely on measuring day length to determine their seasonal timing. A warmer spring, and consequently a higher likeliness of a hot summer, will result in Oak leafing before Ash. A cold spring will see the opposite. As the British know only too well, a colder summer is likely to be a rain-soaked one.”

For more spring gardening tips about heat (or lack thereof), check out Warming Up To The Why Of Gardening, which covers a variety of hot gardening tips (literally) from why mulch disappears faster on a sunny flower bed than a shady one to why heat is so important for growing tomatoes.