When you wake on a winter morning and look out onto your garden, a crystallised sheet of white may be spread across the ground. If you live in a colder place this frost might extend upwards and over all your plants in a hoar frost – when I lived in Armidale NSW I saw such an icy spectacle one morning and was entranced. Then went back inside to my heated house!
Recently my comparatively warmish patch in Bellerive has shuddered with occasional sharp cold snaps – which always leads to blue sky gorgeous days. A superficial layer of frost remained on one particular morning until almost 10am. I scurried out to take the photo and then back inside to stay warm. Only the ground was white while my plants seemed undisturbed.
Usually, white across the ground means that the surrounding plants will be affected. If some of their cells have frozen and then thawed, the sight can be a sad one – limp, lost looking plants. Usually as the day warms they bounce back, but not always. Sometimes sufficient cell life or plant structure is killed off and the plant will die.
This website explains that during a frost ‘ice crystals form on the surface of the plant (“white”). The water in between plant cells freezes and draws water out of surrounding cells to form more ice’.
If you think of a plant’s operating systems, these include Xylem and Phloem channels which bring nutrients and water up from the ground and distribute the sugar and mineral effects of sunlight and photosynthesis down from the leaves through the plant to the roots.
This system operates in a vacuum and if a bubble of air gets in or the gases or liquids can’t move because some cells are frozen for too long, the chain of action gets broken and there is no way in the world the plant can remove the air bubble or restart the flows. That means death.
West of Hobart , the town of New Norfolk is nestled in a stunningly beautiful part of the Derwent Valley. Friend V has suffered many plant losses over the past weeks due to heavy frost in the Fairview area. Vi ‘s photograph’s show the remains of a recent frost. The crystallisation around plant leaves is clearly evident on part of her arum lilies and geraniums.
The wilting below is clear on other arum lily leaves with some leaves curling up in horror.
New shoots on the passionfruit vine are softly frosted; soft to the eye and very hard on the plant.
It is the flowers of her white flowering daisy that have been affected; they look wet and limp.
Sister J sent me a sad story telling photograph of her jasmine showing frost burnt leaves.
Mostly these plants will go on to thrive. However in a climate of increasingly severe contrasts – from temperatures in the minus degrees in winter to the plus 40 degrees in summer, I suspect we will all need to reconsider which plants will be able to live here in southern Tasmania. Wishing and hoping that the climate will return to the more moderate nature of the past will probably become increasingly foolish.