Australian Tree Fern. This is the hardiest variety of tree fern available and can survive outdoors in a sheltered site. Protect with fleece and straw during winter. Beautiful deep green ferny fronds unfurl from spidery knuckles in spring and summer. With age it grows a trunk that can reach 3m+. Best in moist, humus rich soil in part shade and a sheltered location. These have two stout trunks growing together, 6ft + 2ft.