How to recognise it
Cold temperatures, and particularly frost, can cause a wide range of symptoms, to the extreme that the plant may simply collapse and die with no prior warning.
Leaves grow with yellow edges (eg anenomes, sweet peas), almost white (eg many bedding plants) or white banded (eg narcissus). Dry areas on the leaf can develop and evergreen foliage may brown completely. Some leaves may redden in response to cold temperatures, which is sometimes seen as an advantage.
Where frost has been present leaves can be puckered, withered or discoloured (often blackened) with a silvery appearance on the lower leaf surface. Petals can also be withered or discoloured and may start to rot.
On stems, brown dry patches can develop (particularly on Acer spp.) and they may eventually blacken, wither and crack or split (which can lead to die back of the stem). If moisture then accumulates in the crack and freezes again this could lead to the death of the whole plant.
Frost may also lead to plants being lifted as the frozen soil forces the plant upwards. This can happen, for example, with overwintered vegetable crops.
Potato tubers, particularly those in storage, can acquire chilling injuries which appear as small blackish patches on the flesh, although these can equally be caused by other problems such as viruses.
What causes it
Generally a sudden cold snap in autumn or spring, or particularly low winter temperatures. It may also be caused by keeping plants in the wrong environmental conditions over winter (eg leaving tender plants outside).
Why it’s a problem
Low temperatures slow down the plant’s growth.
Frost can cause additional problems, such as above ground parts of sensitive plants collapsing altogether (due to ice forming in the plant cells and ‘bursting’ them as it expands). Less sensitive plants will only be affected in the buds and developing leaves.
In severe cases the whole plant can be killed.
Where you are likely to find it
All plants could potentially be affected by this, although they vary markedly in their tolerance of low temperatures. Seedlings and young plants are particularly vulnerable.
How to prevent it
Ensure that you know the temperatures which your plants can withstand and move those which are not frost tolerant indoors either permanently over the winter or whenever there is a chance of frost. Select plants which are appropriate for your area, eg later flowering fruit trees and bushes.
Be aware of frost pockets and exposed locations and avoid planting more tender plants in those areas.
Physical protection can help plants survive very low temperatures or frost. This can take many forms such as fleece, straw insulation, cold frames, cloches or earthing up. On a professional scale heaters can be used to protect blossoms on valuable trees in orchards.
Be careful not to walk on frosted lawns as you will cause more damage to the grass plants than the frost will.
How to get rid of it
When entire plants are affected they will not recover. If only some leaves are affected these can be picked off and composted (so long as no diseases are present).
Is it good for anything?!
Yes, it can turn your garden into a winter wonderland, with frost glittering off grasses and the enhanced colours the cold brings to some plants (eg the blue tinged foliage of Cedrus deodara ‘Feeling Blue’).
Other useful information
Most spring frosts are ground frosts, therefore shelter belts, although effective to reduce wind and air frosts, provide no protection from spring frosts.