On 29/12/2020 16:24, David wrote:
We have two apple and two plum trees in plastic pots,as a holding position
until we plant them out.

Planted (I think) around August from smaller pots.

The ground now is very wet after all the rain, but not frozen.
I understand that dormant fruit trees can be planted out almost any time
the ground isn't frozen.
However I may be wrong.

Trees in pots have done OK over previous years, so I think that they are
safe from cold and frosty weather.

The dilemma is if it is better to wait until the ground dries out a bit,
or if it is better to plant now and remove any risk of frost getting to
the pots.

Three pots are 13" internal diameter and the fourth is 18".

The trees are small enough that I could bring them under cover (plastic
roof with the sides open to the elements) but I'm not sure that this is
necessary.

Coastal East Anglia so generally quite mild.

I doubt most deciduous trees would suffer any damage at all from frozen
roots, but they should not be disturbed:
https://www.ashridgetrees.co.uk/blog/caring-for-bareroot-plants-in-cold-weather

In my opinion, far greater damage would be done by planting in
waterlogged soil. The roots would probably survive a week in soaking wet
soil, but after that all bets are off.

This ref tends to disagree somewhat about frozen roots:
https://www.keepers-nursery.co.uk/helpdesk/fruit-tree-advice/what-to-do-when-you-receive-your-trees,
but does make the point that you should not plant out in waterlogged
soil: "... Waterlogging is often a more serious problem. If your soil is
prone to waterlogging it is best to plant in late winter/early spring
when the ground is starting to dry out. "

I would wait, and give the pots some protection - perhaps wrap them in
bubble polythene.

--

Jeff