Sunday, July 13, 2008

A living fossil

A cycad was one of the first plants we bought for the garden and was also the most expensive.

In the first year we thought we'd lost it but fortunately in the second year it responded by producing a new set of leaves. Each year, at about this time, another new set of leaves appear from the centre and within weeks grow to full size. Our cycad enjoys shade and protection from the elements.

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This year's new leaves

What is a cycad?

Cycads are a small group of plants with many unique features, an ancient origin and a very long history. Cycads are known to have lived in the Permian era, over 200 million years ago - even before the dinosaurs roamed the earth. Although once abundant across the globe, the cycads are now greatly reduced in both numbers and distribution. There are now about 250 species in 11 genera, compared to possibly 300,000 species of flowering plants, the group that now geographical range.

The very large divided leaves means that cycad plants resemble palms or tree-ferns in overall appearance. Cycads, however, differ greatly in almost all aspects of detailed structure and reproductive behaviour. Cycad plants are dioecious (i.e. male and female reproductive structures are borne on separate plants), and reproduction is by seeds, which are produced on open carpophylls or seed-bearing leaves. Although technically woody plants, unlike other woody plants, cycads possess a pachycaul stem. This is a thick, soft stem or trunk made up of mostly storage tissue with very little true wood. Within the trunk, leaf traces or veins leading to leaves arise at a point opposite the attachment of the leaf, and circle the trunk within the storage tissue. These are known as with girdling leaf traces, and occur in some ferns but no other seed plants. The coralloid roots of cycads are also characteristics not seen in other seed plants, and the cycads lack the axillary buds seen in other seed plants.

We have no idea whether ours is a male or a female plant and since nobody else nearby has a similar plant we probably will never find out.

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