The blackthorn’s breaking bud, camellias are blooming and Magnolia soulangina is opening globes of gleaming alabaster petals… so there’s a frost on the way
This year the spring has come early: sadly we may be paying for balmy March days earlier on and a warm winter. After the soaking last year trees and shrubs have made up growth which was suppressed in the almost forgotten eighteen month drought and laid down flowerbuds like never before – but what looks like being one of the most spectacular springs for many years might be cut down before it barely starts.
In Germany wine growers are fretting as the grapes are emerging a month early – they could either have a marvellous vintage or none at all.
Fragile flowers are often destroyed by a cutting East wind with below zero temperatures, turning them brown and dying overnight just as they begin to unfurl. Usually buds are safe if unopened, but pollen may still be killed. Frost damage also allows entry to damaged plant tissues by infections such as Monila or Botrytis.
Stone fruits, including plums and cherries as well as the more obviously tender peaches and apricots are vulnerable, as are blackcurrant bushes. Frost damage in barely opened blackcurrant flowers leads to ‘runoff’, when fruits appear to set but drop within a few weeks.
Limiting frost damage is never easy – on mature trees practically impossible – but home growers can protect seedlings or smaller bushes with horticultural fleece, netting or other covering material.. At this time of year the earth is warm enough from increased day-length to protect covered plants from all except the most severe convection frosts,when cold air plummets down from a clear sky. Still air means cold sinks rapidly, while even a small breeze can ward off the worst of the cold. Victorian gardeners had ingenious method of protecting crops from using angled tiles to top walls and deflect frost outwards, thus maximising the heat stored in the bricks, or having a wire at the top of the wall from which netting could be suspended to protect espaliered trees behind it.
Will Sunday night be as bad as the weather-forecasters prophecy? watch this space….