Alison AplinManaging frost in your garden

It is the lack of through-breeze that is probably the most significant factor in whether a frost will settle in your garden. My former garden in the Clare Valley of South Australia is situated in a low lying pocket in a region that is relatively high in altitude. Because of the topography of the region, this garden is situated in a dumping ground for gale force winds from the west. In order to reduce the impact of these winds, windbreaks had to be planted along the western boundary.

Frost photo supplied by informed

Frost photo supplied by informed

Unfortunately this also reduced the through-breeze, with the frost settling more readily in such a garden, than maybe the garden next door which was left more exposed. Because this former garden experienced frosts as low as ­10ºC, the objective was to manage the frosts through wise plant selection while limiting the gale force winds, desiccating to an exposed garden.

It is remarkable how the canopy of trees can have a profound effect on air movement – even the framework of deciduous trees is better than nothing. Not only is this framework essential in a summer garden, especially for those further inland, but this framework also proved its worth in the garden over the years during winter.

frost on a spider's web

Under-planting beneath these trees in garden beds exposed to the east is more likely to be frost affected than those facing west. This is because the easterly facing areas thaw more quickly than on the opposing side, and it is the quick thaw from the sun that often causes damage to plants.

Frost damage is more likely to occur when the plants have been well irrigated in autumn, and even during dry winters. When nature is left to manage on its own, it is remarkable how effective this can be – we just need to be more observant of how this is being done.

Frost on black Ophiopogon Photo by wallygrom

Frost on black Ophiopogon Photo by wallygrom

The leaves of plants are full of cells. When these cells are full of water (following supplementary irrigation), it is this water that swells when frozen. If the cells are kept dry, as nature intended (when it doesn’t rain for instance), there is no water to freeze and hence swell and so the damage is significantly reduced.

‘Black frosts’ are far more damaging than the rime frosts that are more evident. These ‘black frosts’ are prevalent when drought is impending and are usually associated with a dry winter. Nature intended the affected areas to remain dry for a reason, so that the damage to the plants’ cells is reduced.

‘Black frosts’ are often not noticed until a few days later when a particular plant can appear blackened. Vehicles that are left out overnight will have ice on their windscreens whereas none will be evident on the ground in such a frost. They are always higher off the ground with the damage occurring above ground level. Don’t irrigate your garden in frost prone regions during winter – it is dry for a reason.

Another very important strategy to consider is how you irrigate and manage your garden during the growing season. In frost prone areas, it is essential to “harden” the plants leading up to winter. The best way to do this is to irrigate your garden very infrequently, say every 4 weeks, but for at least 3 hours at a time. This is the best way to harden the wood of susceptible plants, and it is remarkable how well this strategy works.

Once the night temperatures drop in autumn allow nature to take its course. If your garden needs extra water at this time, it is suggestive that you have chosen the wrong plants for your site which are not compatible with the climate, the soil or both. New plantings can be hand watered to get them through til winter sets in.

Gardening is not hard if you allow nature to have more control. The role of the gardener is really only to observe, and give a guiding hand where necessary. The sustainable garden isn’t heavily pruned or controlled in any way. It can still have its formal elements, but even these are more natural and uncontrived. Leave nature to take control and enjoy the pleasure of observing.

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Alison Aplin

About Alison Aplin

Alison is a passionate, multi award winning sustainable landscape designer, Horticulturist and arborist. She has been the owner and designer of 2 Ecotourism gardens that have both won significant awards. Her writing is based on knowledge, empirical learning which is essential to sustainable ethic, and a questioning mind leading to much research. Her articles are often controversial - with a disclaimer that she is responsible for the written matter, and not Garden Drum. A deeply caring person about the natural environment, Alison's writing endeavours to explain why sustainable landscapes are so important. Without people like her, they will be lost and gardens will become merely concrete

4 thoughts on “Managing frost in your garden

  1. This is very considerate and eventually labour-saving advice. And of course, a garden makes most sense if not impact when its inhabitants naturally belong there with regard to climate, soil and other general conditions, which also applies to “hardscape” material.

    Yet, we gardeners sometimes want to push boundaries and like to experiment but we then have to accept nature when things go wrong. And sometimes we curse prolonged observation periods as I did definitely during my recent 4-week spell in Germany. The ground was still completely frozen at a time when in other years the fruit trees would start to flower and the spring bulbs would have reached their peak. But it was extremely interesting to observe hitherto unknown mini frost pockets and also to realise that sun-facing sides can have severe disadvantages, too, where snow and ice melt first and frost then returns to uncovered areas. It feels a little awkward that you have to protect some plants from the very sun you have been desperately waiting for…

  2. Thanks for your feedback Bernhard.
    It does seem such a shame when that longed for sun, when seen early on a frosty morning can cause such damage to plants incorrectly placed. It is a learning curve for all of us.

  3. In Britain people plant to roll the frost down the hill, leaving a gap for it to pass through. This is because it will flow down like water, but is not a solution if you are gardening at the bottom of the hill! Again it is acknowledging nature’s role.

    • I totally agree with you Virginia. We also left openings within our very frost prone garden to try to allow the frost to maintain momentum down the hill. But as you state, it is the plants at the bottom of the hill that one needs to select very carefully.
      I have had people tell me that they shroud many of their plants during winter to stop frost damage. I like to enjoy a winter garden as much as any other time of the year. I personally really love the winter garden. If the plants are covered because of inappropriate plant selection, to me, it defeats the purpose of gardening. Gardens are for all seasons surely.

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