Posted: 01/11/2013 at 07:53
Personally with Tree Ferns I wrap with fleece when it is forecast to be minus temperatures only. An old duvet over the frowns when it is forecasr below -5C is all that is needed to keep the fronds from browning - I am not as mild as coastal Devon but milder than a lot of the UK.
You have quite a mix of plants next to each other, am guessing in pots as they have different needs:
Phormium - well draining but damp soil, sun to part shadeTrachycarpus - Very well draining soil, full sun
Bamboo - moist soil, sun to semi-shade
Acer japonica - moist well draining soil, out of the wind, semi-shade
Dicksonia antartica - damp soil, semi-shade
Heuchera - damp soil, semi-shade