How do plants cope with cold winters

A.� It varies from plant to plant, but one rather good analogy that has been used is that of a business. Some plants have built up enough stocks before the arrival of winter that they can afford to shut down altogether until better weather arrives while others scale down production during the leanest months.

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A. According to scientists, the crucial temperature for plants is five degrees Celcius, or 41degrees Fahrenheit. When the thermometer goes below this most plants slow their metabolic rate right down and become dormant.

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A. The evergreens are the plants that continue to function, albeit at a reduced level, through the winter. To do this they need to be able to transpire, to allow water and waste products to evaporate through the leaves. That's not to say they don't shed their leaves, they do, they just do it constantly throughout the year.

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Deciduous plants shed their leaves because they are going into dormancy and don't want to lose moisture while they are shutting down for the winter. Their leaves also tend to be more delicate than those of the evergreens and when they die could spread disease to the rest of the plant if they stayed on it.

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A.� There are often casualties, especially if a particularly mild autumn has encouraged the early development of buds, but Mother Nature has�come up with ingenious methods to ensure they survive the winter.

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Many alpines have hairy leaves that form tight, protective clusters around the buds inside. Perhaps the most remarkable though is the rhododrendron, who actually free dry their buds like we do instant coffee. The sap is drained out of the bud as soon as the cold weather sets. Then when spring arrives and the sap begins to rise again the buds are rapidly rehydrated, causing them to burst open.

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A.� Freezing is one of the greatest threat to plants. Above the surface the water in plant cells solidifies and causes those cells to rupture. Below the surface, especially with evergreens in containers, a frozen root ball means the plants can't get the water it needs, causing a drought in effect.

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