These are my observations at Jungle Heights

-My Garden

"But anyone who practices organic gardening knows that it is made up of a huge volume of hints, tips, ideas and practices—some of which, when tried, work and some don't, despite the fact that the organic gardener just down the road did exactly the same thing and got incredible results. " 

Perelandra Garden Workbook

C. australis is commonly known as the Rough Tree Fern due to the presence of adventitious roots, tubercles (knobbly bits) and masses of hair-like scales on its ‘trunk’. The horticultural appeal of C. australis is not only due to its beautiful looks but also because it is an extremely hardy species, even capable of tolerating direct sun when the roots are wet. It is also a robust tub plant and is unusual in that it is tolerant of salty winds. C. australis is thus a popular, cold-hardy tree-fern, adaptable to a variety of climates and soils.

C. cooperi is quite distinctive from C. australis in that it has a more slender trunk with distinctive "coin spots" where old fronds have broken off the trunk. C. cooperi fronds are bright green and lacy and tend to be very fast growing.

- Tropicbreeze / Australia

How Do I Grow my Tree Ferns

I learned from in passing conversation that the fern stalk, particularly the fuzzy part must be watered every day, as the fuzzy parts (I'm sure I'll eventually learn the technical name for that) are actually part of it's roots (besides that particular designation -fuzz and root). Since I've adopted that method the Fern is absolutely in the top of the vigorous growing plants in the garden.
Having said that, I have been observing closely the number of fronds produced at a time, when the fronds suddenly change from 2 to 3 in quick succession (for a fern) to one at a time and a noticeable slow-down in the vigor. It appears to be directly related to that watering technique, and when a couple of days go by, or it is particularly hot and the water dispensed was probably insufficient will have rather immediate effects on the growth behavior.

Here is my theory that is directly tied to that water intake: I noticed that one week was forecast to have rain every day here (in fact none of them did) the fern slowed in growth for a couple of weeks after, producing only 1 frond, and then that took twice as long as the previous watering pattern of "fuzz everyday". I observed was that the trunk tightened up in the area the fronds came from, retarding the fronds exit. In fact, one frond actually became stuck n the passage, and when it finally emerged, it was malformed and stunted. By keeping the fuzz well watered it acts a bit like a sponge, and expands and swells relaxing the exit area where the new fronds emerge. I suspect this reaction is probably a coded emergency factor in the plant, perhaps bracing itself for a dry period??! conjecture, but it seems plausible. Since that observation I've been ever vigilant about watering the center trunk area, often when exceeding 90F two to three times a day with about 1 gallon of water each time. This has resulted in that continued swelling of the exit area, followed by a counter clockwise rapid production of fronds most noticeably 2 to 3 in rapid succession. Each frond faces each other and grows in the opposite direction of the last frond, maintaining a counter clockwise rotation.

Sunlight also plays an important role, and I've noticed a difference in frond production when the sun shifts from the spring to summer position. The older the Fern gets, the better it seems to be at tolerating more direct sunlight.

It's taken me a couple of times to get it right with the fern tree, and in fact had given up on them for a while until I found a scragly fern tree at home depot that was in the liquidation pile. 

I planted the fern by the pond, building up a special section with a stone border, to ensure good drainage. The first year and a half the fern seem to be doing reasonably well, adjusting the watering amounts several times. After losing my first fern tree from over watering I think. I over compensated on this one too much, and nearly lost this one by not watering enough.

THEN, the most important care technique was revealed to me as PalmBob talked about in his comments. Watering the trunk daily, keeping it moist. This turned out to be the holy grail in terms of growth behavior I've seen. In spite of a rare hard freeze this spring, damaging the bird of paradise that is adjacent to the fern tree, the fern tree itself did not flinch, wilt or otherwise display any distress. This is not to say that I don't pamper it when I know what the low temperatures are going to be, but the freeze took us all by surprise. 

Watering the trunk, or keeping it moist daily resulted in almost immediate changes in the growth behavior. From last fall, to this summer the fern has doubled it's size several times! The fronds, or fiddles now stretch to 10 feet in the air, 2 1/2 feet wide. Taking quite a few pictures, I'm smiling this month looking through pictures of May, thinking then, just how awesome and big the fern was. It's twice the size now, and the trunk is now 1 1/2 feet tall, having started the year with no measurable trunk.

I've noticed that after the third year or so, the plant seems to toughen up a bit.

*** When planting the fern tree, plant shallow, build up the area with a leaf mold potting soil that can be purchased at nurseries. Ensure that the trunk is well above the soil line. Even though it requires watering daily, it will not survive if the trunk is encased in soil.****

It still amazes me how something so simple as keeping the trunk moist makes such a profound difference. I soak the trunk every day when it's in the 90's, at least a gallon of water or more. It is my opinion that this also facilitates the fiddles being able to clear the trunk area faster and with more ease. When the trunk is not damp, it tightens up the area where the fiddles grow out, slowing down the process. Of course, this is just my experience on my one large fern tree.