They are the traditional sign that the icy gusts of winter are easing and summer’s warm breath is only a few months away. But this year there are almost none to be seen.

Spring bulbs that would usually have caused thousands of flower beds to burst into colour last month have been delayed by up to six weeks because of the unusually cold winter, leaving many gardeners to guess whether spring, marked by today’s equinox, has really sprung. An average mean temperature for March of 2.4C (36F) — about 4C below that for recent years — has meant that many early flowerers such as daffodils, crocuses and hyacinths have kept their buds firmly closed.

At the opening of the Spring Bulb Festival at Kew Gardens visitors were disappointed to find that only a handful of the 100,000 February Gold daffodils that normally line the boardwalk were out.

Common crocuses, which would normally have finished by the middle of March, are just starting to bloom, and hyacinths, which would also usually be out, are only now appearing above ground, and are this year expected to flower through until mid-April.

“There have been no substantial mild periods this winter and as a result not the requisite number of days above 6C which are necessary to stimulate plant growth,” Nigel Taylor, the curator of Kew Gardens, said. “With the exception of one warm period at the end of January, it has been continuously cold since November.”

“The lack of precipitation, particularly in the South East, has also meant that the plants have not benefited from the insulating effects of snow, which would usually act as a blanket and protect bulbs underground from cooling down too much.”

The late arrival of spring may have a silver lining. Experts suggested that some aphids and other sap-sucking bugs may have been killed off by the long winter. Bulb varieties that usually flower separately will now bloom together and provide an extra spectacle.

The Met Office said that the slow arrival of warmer weather did not indicate any trend towards seasons being delayed. The last eight winters had simply been unusually mild and the colder temperatures this year had been a result of weather being blown in from the North East, across Siberia, rather than the South West, over the Atlantic Ocean, it said.

“People have been lulled into a false sense of security. It is not unusual to have temperatures this low in March,” a spokesman said. The average temperature for March for the eight years before 2006 was 6.1C, some 1.4C higher than the 30-year average.

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