Plants not tricked, just pressing on

A109 Light Utility Helicopter flight with mayor Gisborne City from the air in November 2023.

Opinion

I wish to correct some misunderstandings about late flowering/fruiting in trees and plants.

Plants are not “fooled” into thinking spring has arrived — they are simply continuing to make the most of favourable conditions to reproduce.

The key word is “continue”.

The seasonal behaviour of plants, and indeed, insects and higher animals, is locked into their genes.

Plants respond to both external and internal factors — temperature, day-length and sunlight for instance, as well as attack by disease or other organisms, browsing or grazing and so on. The response is controlled by plant hormones which govern all the major functions of growth.

A plant will continue to grow, flower and fruit so long as hormone production is not changed by certain “triggers” such as a shortening of day length, or a drop in temperature.

Gisborne has been enjoying very warm days and clear skies, producing long sunlit days.

In an average year the temperature would have dropped by now, cloudy conditions would have shortened the length of daylight, and there may even have been a frost or two. This would have triggered hormone responses to send trees and plants into winter hibernation.

Instead, plants have simply continued to use the mild autumn to maximise growth and seed production.

Insects such as ants and flies have done the same, getting in more breeding cycles to ensure the success of their species.

The current flowering and fruiting is not the same thing as the early arrival of spring, when plants respond by coming out of their genetically programmed and hormone-induced dormant period.

An early burst of spring can be devastating for some species caught by a return of cold weather and frosts, with the resultant damage to flower and leaf buds.

Worldwide, climate change is affecting plants and animals and many organisms are genetically unable to adapt to the scale of these environmental changes.

Roger Handford