My seasonal correspondent (in that he emails me seasonally, about seasons), Rick Kemp, asked me a few weeks ago whether I thought 1 March was the first day of Autumn.
Rick has thought longer about seasons that me and I'm aways eager to hear his views. As always, he was diplomatic. He knows I favour seasons based on climatic and environmental changes, while he, on balance, prefers what he calls solar seasons (seasons based on distance of the earth from the sun).
I should stress that Rick's solar seasons are not your run-of-the-mill four seasons. He would prefer a series of transition periods between each of our classic seasons, resulting in maybe eight recognisable units. But that's for another day.
The last email, in late February, was all about when autumn starts in Sydney. Rick first presented the case for tradition, at least in Australia, where autumn starts on 1 March.
Our calendars say it's autumn so it must be. April and May are the autumn months. More interestingly, Rick observes some of the 'indicator plants' of autumn are doing there thing. Sasanqua camellias are starting to flower, Freesia leaves are emerging from the soil and autumn crocus are blooming. I noticed myself that Plane Trees leaves are browning at the edges, getting ready for their autumn drop.
Alternatively, using Rick's 'solar seasons', autumn (or the transition season leading to autumn) has already started with the rapid shortening of photoperiod, particularly in the afternoon. Rick feels there is less need of a shoulder season between summer and autumn than there is between winter and spring.
The third alternative, and my preference at the moment, is that summer continues until the end of March and we have a short autumn in Sydney, from April to May. As Rick noted, it still feels like summer. In many Northern Hemisphere countries the Equinox (around 21 March) is used for the start of autumn so in that system there are plenty more weeks of summer left. In Australia, we now finish Daylight Savings on the first Sunday in April so that's a very neat place to finish summer.
I will admit that a week or so ago the mornings began to get a little crisper and the heavy humidity of high summer seemed to have passed, but I'm wary of these temporary weather fluctuations. The heavy rains in early February created a distinctive climatic feel for us in Sydney this year, and who knows what is around the corner in March. Also, are we experiencing a kind of 'shoulder' period similar to early December?
Maybe it doesn't matter, but at the very least I'm observing plants and animals more closely, and I'm judging seasonal changes more by the environment and climate than the cadences of a calendar.
Image: The first sasanqua camellia flowers for 2010 in my own garden. For more on seasons see previous postings.