Coles Nurseries managing director James Coles said winter has not hit yet and if cold weather does not arrive "there is the risk of more pests and diseases later down the line".
Palmstead Nurseries marketing manager Nick Coslett said it is still "extremely mild". Plants have been confused by the mild weather and were later to lose their leaves this autumn, he added.
Crowders Nurseries owner Robert Crowder said he wants a prolonged period of cold to kill pests and diseases, but it has not come yet. "It's great for working at the moment but we don't want the while winter mild."
Johnsons of Whixley director Andrew Richardson said the mild weather has been "conducive to getting plants in the ground". He added: "It has been mild and wet and we've not had any winter frosts so the problem on the nursery is with spraying and cultural issues."
The Met Office said autumn temperatures were 0.6 degsC higher than the 1981-2010 average at 10 degsC. Rainfall was 88 per cent of average. UK mean temperature was 8.2 degsC in November, 2 degsC above the 1981-2010 long-term average, making it the third warmest November since 1910. The south was 3 degsC above average. The UK overall had 145 per cent of average rainfall, concentrated in the north.