The optimal time to prune evergreen plants is after the beginning of May, once they begin to grow strongly.
Gardening expert Helen Yemm makes her comments in the Daily Telegraph, explaining that the new growth on such flora has a tendency to be sensitive to frost and that British nights are not warm enough for them until this time.
She adds that horticulturalists will rarely kill a shrub by pruning them too hard, but notes that it is possible to "upset them and make them temporarily hideous" if they are cut back to a great extent.
Concluding, Ms Yemm explains that the majority of ceanothus plants do not respond well to major pruning and require regular smaller trimming after flowering to help them flourish to their full potential.
Meanwhile, online gardening resource Doctor Greenfingers states that March is the ideal time to prune back roses, early-blooming shrubs and large-flowered clematis.