May Frosts?

Last night the temperature failed to fall below 13 Celsius (55F), the mildest night since 16th October. No doubt the Garden Centres will increase their sales of bedding plants, helped by the occurrence of the holiday weekend. However, before last night, there were 2 nights with ground frost. In this part of the country, there has only been 1 May during the last 20 years when ground frost was not reported, and in 2 years there were damaging air frosts with the temperature falling below minus 1 Celsius (30F). A few years ago, a well-respected local gardener said 'never put in frost-prone plants before 17th May'. Good advice, well received.