Cycas pruinosa

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Figure 1. C. pruinosa near Kununurra, WA.

The specific name, pruinosa, means covered with powder and aptly describes the blue-white ovules of this plant. Officially named in 1978, this unique Cycas is probably the nearest relative to the south-east Asian species of Cycas. J.R. Maconochie persistently mentions the pronounced revolute margins of the pinnae and although this does not make it definitely allied, my photos looking down into the female seeds show other similarities. For instance, the very ferruginous nature of the end of the megasporophyll. It is pinnate, dentate and has between 20 to 30 soft teeth of 25mm long. The apex does not sharply crown in the female as in Cycas media, but it is rather obtuse and to a point. Opening slowly it reveals the green four to a megasporophyll ovules with slightly oval shape. They mature to bluish-white and heavily dusted with powder. The seed development has C. revoluta similarities.

Figure 2. Male cones.

Furtherto this, the stout trunk which is from 60cm to 2.0m in height, is crowned with arching fronds, distinctly curved from the apex and V-shaped in cross-section. The colour of the pinnae and glaucous rachis is bluish grey in most specimens, but leaning toward the blue. The male cones are narrow, rather deltoid and about 50.0-60.0cm long. The heavily powdered female seed is about 40.0mm long and 35.0mm in diameter. Mature fronds are approximately 1.0m long and with an average of 120 pairs of pinnae on each rachis.

The newly emerging megasporophylls are rusty brown and when fully extended recurve backward having a coating of blue white powder on all seed ovules. The formation of seed and toothed megasporophylls in the apex of the female crown is very interesting and again has some likenesses to the exotic C. revoluta.

Good stands of this species can be found on the hillside above the car park at Lake Argyle in Western Australia. It is also found in valleys and surrounds in the area. The habitat seems to occupy an area from Argyle through Kununurra to the mouth of the Ord River districts, plus sightings mentioned by Maconochie being The Grotto, Carr Boyd Ranges, Kununurra, Ivanhoe Station, Middle Springs, Deception Ranges, south to Hall's Creek and Springvale Homestead. Sightings have been made in the sloping hill country. Up to the time of this writing this species is not common in cultivation. One very important feature not previously mentioned is the existence of two distinct colour forms of this Cycas growing in basically the same areas; one a definite glaucous blue, the other rather grey-green.

Figure 3. Cultivated plant, Katherine, NT.

The Napier Ranges are on the western edge of the Kimberleys, Western Australia, and a few hundred kilometres from the Argyle Gorge country. Nevertheless, there exists within this range a substantial colony of Cycas that with only a few minor differences is at least a form of Cycas pruinosa.

The basic geology of the area is limestone and in at least one situation an entire hillside has no other prominent vegetation except a large colony of these cycads. Spinifex provides the ground cover throughout much of this particular habitat and the plants grow between the exposed boulders and ridges of this very ancient reef. Apparently the exposed boulders have been weather-worn, lichen covered and badly discoloured by time. First reports were that the rocks were basalt but this has since been proven incorrect. Both blue and green forms of this Cycas are evident as has been seen in the Argyle and Ord River sightings. The largest plants observed are about 2.5 m tall and with stout caudices.

Ron Smith, nurseryman, mentions the pronounced visual similarities these plants have to the exotic Cycas revoluta; This being even more so in the green form. Apart from the now well known similarities of the narrow revolute pinnae and the 'nesting' crown habit of the megasporophylls, this Cycas produces many offshoots around the base of the caudex as is common in such exotic species as Cycas revoluta, C. circinalis and C. rumphii. Much of the seed now distributed throughout the nursery trade has come from this source and already the blue or green fronds are visible in resultant seedlings.

Contributed by:

L. P. Butt
D. Stallard (Figures 1&2.)
Gary Beaumont (Figure 3)

External Links:

Cycad Pages, IUCN, JSTOR, Trebrown

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