But it is essential. At this time of year the new fronds are a mass of tightly coiled, hairy, brown constructions in the centre of the previous year's fronds. If they freeze hard, they die. But if they dry out they also die. Providing the apical meristem, buried deeply at the top of the tree fern 'trunk', survives, new fronds will develop and thrust their way through the remains. But you'll lose the early flush for that year - and it's usually the best one.
So, some mornings, when the temperature edges up to around 4-5C or slightly more, the centre gets a soaking. So that this....
|Tight furled young fronds of Dicksonia antarctica|
|Opening frond of Dicksonia antarctica|
...and flush to produce another year's shuttlecock of fronds.
|Emerging fronds of Dicksonia antarctica in May 2011|