This genus offers some marvelous options for tree fern enthusiasts, whether new to the experience or experts in the genre, gardening in Zones 9 and 10 as well as those with a dedication to enjoying and overwintering them in Zone 8. Named for James Dickson (1738-1822), the genus has 22 species from montane tropical sites in the South Pacific with temperate relatives native to New Zealand and Australia. The type species is from the island of Saint Helena, which is probably better known for its association with Napoleon's final exile than for its botanical wonders.
With spreading canopies of bipinnate-pinnatifid to quadripinnate, leathery, 6- to 8-ft. (1.8- to 2.4-m) fronds, dick-
sonias are recognized by the hairy aspect of their skeletal support structure as well as a complete lack of scales. Trunks are slow growing and slender in their basic vascular structure, but are broadened significantly by the bundles of roots that extend in a linear cloak from the trunk's apex to water and nutrients in the ground below.
Spores are carried in miniature cups along the frond's margins, but are relatively short-lived and for best results should be sown as soon as practical after ripening. Logs from the trunks of Dicksonia antarctica are propagated much as one would root cuttings, albeit of a size well beyond the traditional concept of cutting material. Britain's Martin Rickard (2000), an experienced and successful tree fern propagator, recommends sinking
logs in moist soil (no deeper than necessary to keep them upright) and shade. Daily and thorough watering of the "trunks" is mandatory. Once they are rooted, they are ready for Zone 9 or 10 garden sites. Elsewhere they need winter protection, which can be provided by an insulated wrap. An easy option, when they are juveniles, is to cultivate them in pots. These can be carted for the winter into a cool greenhouse or sheltered garden location until such time as the tree and con
tainer outgrow and outweigh you, the gardener. By this stage, with a trunk of 2 ft. (60 cm) or more, they should be ready for a year-round garden site with a protective winter embalmment.
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