subject: Prevent Frost Damage To Plants [print this page] A frost occurs when the temperature drops below 32 degrees Fahrenheit or 0 degrees centigrade. It is destructive to plants in two ways, water is rendered unavailable to plant roots and the cells of sensitive plants are ruptured. These dangers are linked with the severity and duration of your frost as well as the constitution of the plant, in Britain we leave our Roses vulnerable over winter, whereas in some parts of Scadinavia and N. America straw or sacking protection is crucial.
Late spring frosts which occur after growth has started are essentially the most harmful of all. The danger signs are clear skies during the evening, a northerly wind which decreases at dusk and a settled dry period during the previous few days. The danger to a plant is reduced if there are overhanging branches above, other plants around, heavy soil below and the coast nearby. In frost-prone locations avoid planting fruit trees and delicate shrubs. Provide some form of winter protection for choice specimens.
Frost pocket: A frost pocket is an area this is abnormally prone to early autumn and late spring frosts. It occurs where a solid barrier exists on a sloping position, replace this with an open barrier which allows air through. A frost pocket is also formed in a hollow at the bottom of a sloping site.
Wind: The spectacular effects of a gale are renowned, broken branches , knocked-over pots etc. But the effects of persistent winds are less renowned, lop-sided plants due to the death of buds on the windward side, and small growth due to the cooling and drying effect on the growing point. On exposed sites a windbreak may be necessary, but never use a dense screen. A wall or closed fence will create down-draughts on iether side and plants can be harmed. A hedge, on the other hand, will gently reduce wind speed for a distance of 15 - 30 times its height.
Rainfall: The average annual rainfall is 34 inches in England. Unlike some other areas of the globe there is no distinct rainy season, but October to January are nomally the wettest period. The driest region is the Thames Estuary (20 inches), the wettest spots are the mountains of Wales and Scotland (175 inches). The U.K record, however, belongs in the Lake District (275 inches) in 1954 at Springkling Tarn.
A drought is a period of 15 consecutive days without measurable rainfall, and droughts do occur at fairly regular intervals in Britain. Thorough watering is critical at such times, otherwise plants will suffer or die. Snow is a mixed blessing, a blanket of snow can protect plants which might otherwise be affected by arctic-like winds, but heavy snowfalls can damage or break the branches of evergreens.
Altitude: The height of your garden has an effect on the general climate. For every 600 ft. increase in altitude, the average annual temperature drops by 2 degrees and the start of your growing season is delayed by 3 days. Solar energy decreases whereas both rainfall and wing speed increase.
