Cycas bynoe

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Figure 1. Male in front,female at rear.

This species has invalidly been recorded as Cycas burnsii by a botanical field worker. A great deal of research into the Northern Territory cycads is in progress by the Dept. of Natural Science, so correct nomenclature is imminent.

First knowledge of the existence of the 'Bynoe/Cox Peninsula' species was from an enthusiast in South Africa who had received seed labelled 'Cox Peninsula'. The Darwin Study Group of the Society for Growing Australian Plants, reports that the species in question grows right along the Cox Peninsula west of Darwin and is probably a form of

Cycas armstrongii. Other reports suggest that it could be a natural hybrid of C. armstrongii and

C. calcicola as it displays similarities of both. However, further to this comes information that the larger caudex and growing habits are reminiscent of the Northern Territory giant

C. angulata. Out of so much supposition must eventually come more investigation and more clarity.

Don Stallard, local cycad enthusiast, noted that the first specimens he saw growing, amongst the sand-dunes just back from the beach, and further reports from other sources endorse this. Photos received also show branching trunks on some plants. Referring to field reports sent in June 1987, the details are given below. Approximately 20km west-northwest of Darwin, back of the beach on the Cox Peninsula. The terrain is a typical tropical medium woodland with average rainfall of 1500mm per annum, soil grey brown and sandy, scrub cover being Pandanus, Eucalyptus and Planchonia. The distance from the beach about 100m. Along this beach head the Cycas are growing in scattered groups within a community, preference being for damper fresh water areas in the proximity of large shade trees. Deciduous as in Cycas armstrongii some with new fronds developing. The site had no new sporophyll apparent and no male cones were seen. Very brown tomentum covered back of rachis/petiole and very short pinnae right to the leafbase. Some without hair on the petiole but always on the leafbase. Leaf fronds average 1.10m, the maximum being 1.25m, rachis length average 82.0cm, maximum 92.0cm. Spines up to 40, two to four every 2.50cm, spines located the full length of the petiole. Pinnae average 108 to 113 pairs, length at the top average 6. 0 to 8.5cm, middle 13.0 to 15.0cm, bottom average 9.0cm. Colour of the fronds grey/blue underside and dull, greenish/blue on the top, some having green mottling. All pinnae curved downwards slightly, 5.0m m wide smooth on the margins.

Trunk caudices seen average 2.5m tall, to maximum of 5.0m. Diameter average 15.0cm to 40.Ocm. At least four were branching, and fifteen were suckering. The specimen data shown as maximum represents a plant of exceptional size and branching.

Figure 2. Mature male cone.

Generally the 'Cox Peninsula' species is well distributed and in some cases over many hectares is the predominant plant. Since 1987, further trekking around Cox Peninsula and Bynoe Harbour show sightings and populations of this Cycas throughout the Peninsula and right around Bynoe Harbour following the coast and extending inland possibly to the Darwin River, thence south around Fog Bay and crossing the Finniss River. Sightings cease here, but sightings of a very similar cycad have been seen in the Peppimentari area and Wingate Ranges, which are at least visually similar to the large 'Cox/Fog Bay' species. Recent information from Sharon Chirgwin states: "The Fog Bay/Bynoe Harbour species which may superficially resemble C. armstrongii on closer examination has narrower pinnae, curved at the edges and is so profusely coated with tomentum that young pinnae appear white; This group grows right down to the high tide mark, often in swampy positions, but shows some variation according to locality and environmental conditions. It is often covered with a local orchid, Dendrobium affine. This last fascinating bit of information shows what could be learned if the community at large were not always burning-off our cycads. The Darwin orchid is on the endangered species list. It was once known as Dendrobium dicuphum which is now relegated to synonymy, and now correctly D. affine. In unburned areas like coastal strips, cycads are probable hosts for many such thing.

Figure 3.

Contributed by:

L.P. Butt
Jim Christie (Figure 1.)
K Rathie (Figure 2.)
D. Stallard (Figure 3. from Palms & Cycads No. 27, Apr-Jun 1990).

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