By Larry Hodgson
December 21st is the first day of winter, right? (Or the first day of summer in the Southern Hemisphere*.) Well, maybe. It depends on your definition of winter … and of the other seasons.
*Sorry, Aussies and Kiwis. I’ll be sticking with Northern Hemisphere definitions in the rest of this article, but … at least I did think of you!
December 21st is indeed the first day of winter according to astronomical reckoning. It’s the winter solstice, the shortest day of the year. From there on, day lengths will increase daily.
Astronomically, the spring equinox is around March 21st and initiates the spring season, then the summer solstice takes place around June 21st, launching summer, while the autumn equinox occurs near September 22nd. These are the seasons I was taught in school.
But you can’t necessarily garden according to the astronomical seasons.
Meteorological Seasons
In many temperate climates, it’s already been too cold to garden for weeks, if not a month or more before December 21st. So, winter is already here.
And “spring flowers” may well be in bloom before March 21st, even though it has just turned spring, astronomically speaking.
Most gardeners would also agree that summer—the warm to hot season where you don’t need a coat in order to garden—starts long before June 21st.
As for the astronomical autumn, September 22nd: many of us only use that date to decide when to put our short-day houseplants, like poinsettias, Thanksgiving cactus and Christmas kalanchoes where they won’t receive artificial light at night. In the garden, most of our “fall flowers” have been in bloom for weeks!
That’s why temperate climate gardeners instead tend to use, instinctively, the meteorological seasons. But you may not even have known such a calendar exists, even though it was officially defined in 1780 by the Societas Meteorologica Palatina, an early international organization for meteorology. It defined the seasons as lasting three months and linked them to the Gregorian calendar. Ever since, professional meteorologists all over the world have used this definition. And it goes as follows:
Spring: March 1st to May 31st
Summer: June 1st to August 31st
Autumn (fall): September 1st to November 30th
Winter: December 1st to February 28th (February 29th in a leap year)
To me, as a gardener, that makes much more sense. Although, where I live, March 1st is still pretty darn cold, you can see plants budding up through the snow and, indoors, houseplants are usually already springing into full growth by then, so that feels like spring to me. And I’ll have already been “summer gardening” since about … the beginning of meteorological summer (June 1st). Plus, I bring my houseplants indoors around September 1st, at the beginning of the meteorological autumn, when colder nights threaten, signaling to me the end of summer.
December 1st as the first day of meteorological winter, however, is about a month late where I live in Canada, as I can usually expect snow about November 1st. (Canadian Thanksgiving is held on the 2nd Monday of October rather than on the 4th Thursday of November as in the USA, so we can party hearty without our anoraks, tuques and mukluks.) Still, mentally, I can make December 1st work for me as the first day of winter.
And I figure most gardeners in temperate climates also unconsciously use the meteorological calendar. It’s just so much more practical than the astrological one!
Other Climates
In tropical areas, there are usually (except at high altitudes) only two seasons, wet (rainy or monsoon) and dry and they may, depending on the country, be called winter or summer, although traditions vary.
By almost any definition, though, it’s winter now in the Northern Hemisphere and our outdoor plants are dormant and indoor ones are holding on, waiting for longer days. So, we gardeners have a bit of a break, but I do have to warn you, with days that start lengthening tomorrow … spring is coming!