Saturday, 17 July 2010

Rising from the Dead*


Plants cope with drought in lots of different ways. Some have thick protective skins, others store water in succulent stems or leaves, and many are covered in hairs to reduce evaporation.

A few plants allow themselves to ‘die’, and then spring back to life when the rains come. Of course they don’t really die, but botanists do call them Resurrection Plants.

The most commonly encountered Resurrection Plants are mosses and lichens, like the ones growing on paths, rocks or even your roof at home. They spend much of their time in a dried out state, swelling back to life and colour when it rains (or you pour water on them).

What they do is allow their stems and leaves to lose water and the cells go into a dormancy state – their metabolism is slowed right down and they can survive in this state for up to years.

There are also various flowering plants and ferns that do this, including several species of the Australian Pincushion Lily (Borya) and Rock Ferns (Cheilanthes). The Rock Felt-fern (Pyrosia rupestris) is succulent, has a thick coating of hairs and can be resurrected.

Better known around the world is the Rose of Jericho, also called Siempre Viva (i.e. everlasting), Rosa Mariae, Dinosaur Plant or simply Resurrection Plant. These names seem to refer to a number of different plants, including in North America a selaginella – a plant closely related to ferns – sometimes called the False Rose of Jericho.

The ‘true’ Rose of Jericho is Anastatica hierochuntica, found in deserts throughout the Middle East, including the Sahara, where it rolls around in the wind when dry. It’s also a Tumble Weed. If wetted, it will expand from the size of a small fist to about 15 cm wide.

Unlike the ‘false’ Rose of Jericho, this plant is probably not really a true Resurrection Plant in that when dried all the leaves fall off and just the stems curl up holding seeds inside. It does uncurl when wet, but generally the seeds germinate rather than the stems springing to life.

Anastatica is in the cabbage and mustard family, the Brassicaceae. Presumably the name Rose of Jericho refers to the beauty of it coming back to life. Certainly it looks nothing like a rose.

Image: The ‘true’ Rose of Jericho in its dried state, photo by Nikswieweg - Klaus Polak (copied from http://www.types-of-flowers.org/rose-of-jericho.html).

*This Passion for Plants posting will also appear on the ABC Sydney website (under 'Weekends' or search 'gardening'), and is the gist of my 702AM radio interview with Simon Marnie on Saturday morning, between 9-10 am.

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