The trunk of a tree fern is really just tough compressed roots growing downward through dead organic material left behind by earlier growth. The foliage and terminal shoot high on top is just like any other fern that never leaves the ground. Because such a trunk is porous, it is ideal for epiphytic plants that, in the wild, mostly cling onto trees instead of growing on the shadier forest floor. Even though most epiphytic plants are able to cling to just about anything, many prefer tree fern trunks because they can actually root into them.
The shaggy trunks of Tasmanian tree fern, Dicksonia antarctica, take decades to grow tall enough for smaller plants to be visible below the lush foliage, but are plump enough to host a rowdy party of clinging epiphytes. Most get only about four or five feet tall, with the foliage standing a few feet higher, although some old specimens in Golden Gate Park are more than fifteen feet tall, and very old specimens in their native Tasmania can get nearly fifty feet tall.
The big lacy leaves spread about six feet wide, and can reach twice as wide in shadier spots. Shade also makes the foliage darker rich green. Like almost all ferns, Tasmanian tree fern like relatively rich soil and regular watering. Unlike other tree ferns though, it tolerates frost.