We’re all getting used to the local effects of global warming − garden crocuses and primulas coming up earlier and earlier (they’re flowering already in my garden).

This past fortnight I’ve realized that my efforts to earth up the rhubarb to protect it from frost weren’t working, as frost or no it was cheerfully and energetically pushing up new leaves on long thin red petioles, the leaf-stalks that greengrocers see as  rhubarb.

But I’ve never seen a pond growing over with blanket-weed in January before. Generally it’s an effect seen late in summer, the tangled green mat forming in a rather nutrient-rich (eutrophicated) lowland pond. Each green thread is a flexible cylinder consisting of a single row of plant cells inside their thick cellulose cell walls, with amazingly elegant green spiral chloroplasts inside, hence the apposite and beautiful name of the genus, Spirogyra, drawn and carefully labelled in millions of high school biology exercise books. The strands grow like crazy in warm ponds and ditches, benefiting from the excess of nutrients from runoff in agricultural areas or indeed from towns. The blanket can blot out light from the deeper parts of a pond, killing other organisms living there. But warm enough for blanket-weed in January? That’s something new.