Sunday, July 1, 2012

Dicksonia antarctica, a fern of The Tertiary

Dicksonia antarctica tree fern is native from the Australian states of New South Wales, Tasmania and Victoria. One of the most widely cultivated tree fern by gardeners around the world. Grows seamlessly into any type of soil, both acid and calcareous, provided with a good drainage, a substrate rich in well-decomposed organic matter and a constant supply of moisture in the soil and in the air. It lives well in shade or partial shade of trees, as in the wild is a fern understory. It originated in the tropical forests of the Tertiary with a warm and permanently moist.

Dicksonia antarctica new frond in early May. This and the following photographs were taken in the magnificent botanical garden called the Huerto del cura, part of the immense palm grove of Elche, located in the province of Alicante. All new fronds of ferns as they display  take this spiral form that follows the Fibonacci mathematical sequence. (I recommend enlarge photos with a double click)

Dicksonia antarctica about 25 years in the shadow of the beautiful palm trees from around the world that form the collection of this botanical garden. On arriving, is a small oasis of tranquility amid the bustle of the city of Elche. It live in complete harmony hundreds of species of palms, Strelitzia, cycads, zamias and cactus.

 Dicksonia antarctica trunk is actually a rhizome along with the dried remains of the petioles of old fronds. The 90 inches of the trunk give us an approximate age of 25 years, as this fern grows very slowly between 3'5 and 5 centimeters per year, somewhat faster in the wild where it can easily reach 15 -20 meters height.

Dicksonia antarctica crown with sprouting new fronds spring.

 Another Dicksonia antarctica slightly younger than the previous one with a trunk about 50 inches.

Fern crown before. The fronds may be sterile or fertile and are springing alternately at different times of year.

The fronds have a very short petiole and an ovate-lanceolate tripinnate blade formed by narrow and lanceolate pinnae.

 Dicksonia antarctica pinnae are also subdivided into lanceolate pinnules, inserted obliquely on the rachis of the pinna with a very short petiole.

 The pinnules are subdivided into their small sessile lobes, ie without petiole, finished in a very fine tip oriented toward the apex of the pinna.

 Underside of a pinna with mature sori covered by a bilobed indusium which are situated on the edge of the lobes of pinnulae.

Same seen from above sori nearer. The indusium is up leaving mature sporangia hovering about to unfold and disperse the spores.

Details of the sori of Dicksonia antarctica.

Already deployed and empty sporangium after dispersion of spores. It is very striking is the large number of cells in the ring.

 Spores of Dicksonia antarctica with a nice golden brown and measures quite large.

1 comment:

  1. Thank you for the excellent photographs and description.