This year we have experienced severe frosts which have caused extensive damage to a number of seemingly frost-hardy plants.
Frosts occur on cloudless nights when the clear skies allow heat to be lost rapidly from the soil and plants.
Windless nights increase the chance of frost because there is no mixing of the cold air near ground level with the warmer air which is higher up.
Frost injury occurs not when the water inside the plant's tissues freeze but when it thaws.
The rate at which temperatures rise on frosty mornings affects the level of damage as does the number of hours air temperatures are below freezing.
Water stressed plants or those that are unhealthy for any reason are more prone to frost damage.
When the water in the soil freezes it becomes unavailable to plants. If a frosty night is followed by a clear sunny day the leaves lose water through transpiration though the soil may remain frozen.
This frost injury is called desiccation as the plant can become quite dehydrated.
During severe frosts soil particles can be pushed apart by expanding ice, resulting in the roots of some plants snapping and causing the plant to rise out of the ground.
There are a few precautions you can take to minimise frost damage to your plants.
A simple method to protect small shrubs and precious perennials is to cover them with hessian, old bed sheets or similar.
For larger plants such as citrus trees a protective structure around or over them can be made by attaching hessian or polyethylene sheeting to three or four stakes fixed firmly in the ground close to the plant.
The stakes should be a little taller than the top of the plant so as not to allow the material to come into contact with the foliage.
There are also some very effective inexpensive, lightweight frost cloths available from most plant centres and hardware stores.
Remember to remove the covering the next morning.
Mulching can be equally effective during frosts as it is during hot weather. Straw or other fibrous materials which have good insulation properties will protect the crowns of perennials or the roots of evergreen trees and shrubs.
Frost-tender plants growing in containers can be protected by moving them to a permanent sheltered position for the duration of winter.
Damp soils retain more heat during the day and more readily conduct heat to the surface. Heat conduction is better in compacted soils.
Another action that can be taken when a frost occurs is to spray a fine mist of water over the plants before the rays of the morning sun strike them.
This should gradually melt any ice that has formed and help the plants survive the damaging period of thawing.
Should any foliage be burnt by frost do not prune this damage off the plant. Instead wait until the danger of frosts has passed as these injured leaves and stems will help protect the plant should further frosts occur.
September 11,12: Launceston Horticultural Society's Early Spring Show featuring daffodils and camellias, Evandale Memorial Hall, 8 High Street, Evandale. Saturday 2-5pm, Sunday 9am-4pm.
September 21: Australian Plants Society Tasmania meeting, Max Fry Hall, Gorge Rd, Trevallyn, 7.30pm. David Marrison speaking on the Royal Tasmanian Botanic Gardens' native plant section re-development.
September 25: Westbury Garden Club Spring Flower Show, Westbury Town Hall, Lyall St, Westbury, 1pm-4pm. Official opening 2pm. Entry $2. Afternoon tea $5.
October 1, 2, 3: Devonport Orchid Society Inc. Annual Spring Orchid Show Spectacular, Maidstone Park Memorial Hall, Main Rd, Spreyton.