I do know how to water the soft tree ferns

I acutally do know how to best water the soft tree ferns [Dicksonia antarctica]. Their "truck" is not a trunk at all, just a pile of root matter, which can soak up an amazing amount of water. the shape of the fronds and the way they branch also aid the collection of rain water. So the best place to water these ferns is at the crown, where the fronds grow out of this "trunk" (aka aerial root).

"The funnel-shaped rosette of fronds of D. antarctica may harvest rainfall and make it accessible to aerial roots situated at the base of fronds. This process may maintain favourable water relations independently of a subterranean root system. This proposed strategy of water acquisition is unique for a fern species and may eliminate a need for soil moisture competition with surrounding plant species."

... from Ecophysiology of the Soft Tree Fern, Dicksonia antarctica Labill by HUNT M.A.; DAVIDSON N.J.; UNWIN G.L. & CLOSE D.C.