Blechnum palmiforme is probably the best of all the Blechnums in my opnion. Whilst not strictly categorised as a tree fern, this Blechnum certainly forms a stout black trunk over time (which the Albatross are known to nest in!).
Aspect: This evergreen fern is more than happy in full sun.
Hardiness: There is no doubt that this is a much hardier fern than it’s near cousin, Blechnum cycadifolium. In my opinion it is definitely hardy to around -6 celsius and maybe below this for short periods.