The weather has been unusually gloomy, and the poor light has resulted in some of the spring-sown crops being a week or so later than usual. They will quickly catch up as soon as we get some sun. We are getting some warm days but don’t be fooled: It may be warm in your greenhouse mid-day but the important thing is the night temperature – critically the temperature at dawn when plants set their programme for the day.
There’s a good Hardiness Ratings sheet on the RHS website – click here. https://www.rhs.org.uk/plants/trials-awards/award-of-garden-merit/rhs-hardiness-rating