In article , Eyebright
writes

days getting longer but the blue light is getting weaker until after
the middle of winter and thats what green plants feed on....hang on in
there until after the middle of winter which i recon to be valentines
day...thats the day in the UK the key goes into the ignition as far as
the growing season...only my opinion !

Yes, February 14th. could be described as middle of winter in UK, and a
good time to think about getting things started up in the garden. Winter
'officially' begins on December 21st, the Winter Solstice and ends on
March 21st, the Spring or Vernal Equinox. At the Equinox, either Spring
or Autumn, hours of daylight and darkness are equal, thus of importance
to gardeners and their plants.

Valentines Day also happens to be the anniversary of our wedding in
1953. It represents the start of a new marital year to us as well as a
new growing season, a sort of double celebration!
--
Alan & Joan Gould - North Lincs.