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A large number of shrubs and trees, some large and mature, appear to have died this winter. These losses are far greater than are usually seen even in Britain's coldest weather and will be a surprise to many gardeners.
It seems the December cold snap is responsible. Research during the last century showed much colder winters than this one, for example 1962/63, killed fewer plants. In those cases the extreme cold had followed a gradual cooling through the autumn until extremes set in after Christmas. However, in years when November was mild and temperatures plunged in December, the rapid change wiped out large numbers of plants believed to be hardy.
A paper, published in 1982, following an extremely cold December of 1981, showed that many varieties of roses and even privet hedges were killed. Not surprisingly figs and mature bay trees also died. Among the casualties listed was ceonothus, otherwise known as the California lilac, whose blue flowers light up many suburban gardens in the late spring. This year many mature specimens, up to 3 metres tall, stand black and apparently dead.
What seems to be the cause of these widespread fatalities is that plants have still lots of sap in their stems and leaves after a mild November and have not fully become dormant. The sudden December freeze kills them. One bright spot recorded is that some specimens pronounced "dead" in 1982 were still alive below ground and produced new shoots when all hope had been lost.
