British Columbia: Windmill Palm moldy?

I winterized my windmill palm this year by wrapping it in burlap, I then stuck a small plastic bag (loosely) on the top so the rain wouldn't drip inside and freeze. When I unwrapped the palm, the leaves looked dead and moldy? I don't know what I did wrong. The inside has new growth coming, so I am just going to cut all the dead leaves off and hopefully it will come back. Just trying to figure out what to do next year?

 

The best place to get advice for that is at www.cloudforest.com and click on Northwest Palms. There are folk who grow them all over the Lower Mainland very successfully, and know all the tricks to growing them well. I am under the impression they don't like to be wrapped the whole winter, especially with plastic. I've never protected mine at all, even though I've only had seedlings. The ones I left in pots obviously died, but the ones inground sailed through the last two winters no problem. I've since left that place, but I visit there often, and the Trachycarpus have done very well. Of course, I got my seedlings for free, whereas you most likely bought yours, and would like to protect your investment.