|the garden on 29 December 2017 ...|
The mercury hasn't dropped below -6 C, i.e. only our typical winter low, but I think it's the sheer number of very cold frosts we've had, many of them on consecutive nights.
Usually, we'd get around a dozen or so sharp frosts all winter, but this time around it seems as if there's been a dozen every month for three months (not that we've been at home for most of the winter, but we kept an eye on the house and weather via our webcams and also talked to friends on Skype).
Having only recently returned to Blighty and surveyed the destruction of the plants, I immediately started thinking about heating a small area of the greenhouse during future winters. We also brought back more seeds of sub-tropical plants from our travels, which should do well enough outdoors in our summers but won't tolerate even a sniff of a frost and will need protection throughout the winters.