Newspaper article The Chronicle (Toowoomba, Australia)

Autumn Equinox Brings Seasonal Change

Newspaper article The Chronicle (Toowoomba, Australia)

Autumn Equinox Brings Seasonal Change

Article excerpt

ONE of the things I love most about living in a temperate climate is that we get to experience four traditional seasons.

You only need to look out the window at this time of year for a reminder - the leaves are turning - and while global warming will have an effect on our climate, it's reassuring to know that unless it can tilt the earth's axis, the timing of the seasons will remain constant for all the years to come.

Today, March 20, is the autumn equinox. It's the official start of the autumn season (March 1 is just for convenience), and in scientific terms, it means that the earth's poles are an equal distance from the sun.

Today we experience about 12 hours of day and 12 hours of night.

From today, the earth's South Pole will gradually tilt away from the sun, shortening our days until the winter solstice arrives on June 21.

Then the days will again grow longer until the summer solstice.

Then the ancient cycle will repeat. And repeat. And repeat. They say nothing in life is certain except death and taxes.

When Benjamin Franklin coined the phrase, he forgot about the seasons.

The role seasonal change has on plants is varied.

Flora originating from tropical climates tend to be responsive to periods of wet and dry.

Lots of Australian plants show these tendencies, and many of those indigenous to our area will flower and seed just prior to our wet season in summer.

Other plants respond primarily to temperature, needing a period of cold weather to initiate flowering (vernalisation).

Plants growing closer to the poles, however, tend to be responsive to day length.

The fancy term for this is "photoperiodism".

It's all still a bit of a mystery to scientists, so let's consider how it works in gardening terms: Photoperiodism basically means that some plants are long day length, forming flowers as the days grow longer, and some are short day length, forming flowers as the days grow shorter.

Others are day length neutral.

Onions illustrate this response to day length perfectly. Short day varieties form bulbs after the summer solstice as the days are getting shorter (and night grows longer). …

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