How can I help proctect the above from frost.I have several Japanese plaintains which I wrap in straw and cage with chicken wire. I live Stafford Staffordshire, frosts in Febuary can drop to minus 10-15 degrees.The above is protected behind south facing fence.
Well it's probably ok. However, the more overhead layers, with air in between, the better. You'll only need a few layers of fleece in the worst weather. What you must also protect is the pot it's in. If you've protected the plantains (I presume you mean bananas?), then the monkey puzzle won't present a problem. Once established, they're very hardy.