A bit of the devil in it, to keep the devil off it

In a world ruled by natural selection, plants have evolved many methods to escape being eaten by herbivores. These little tricks take many forms, from poisons like deadly nightshade, to spikes on cacti. At the U of M Conservatory Greenhouse I've noticed one particular plant that displays an unusual trick to fool animals that would otherwise eat it in its youth.

The leaves of the juvenile lancewood plant from New Zealand are about as photogenic as they are appetizing -- in other words, not at all! The serrated leaves are stiff and barbed. They also appear to be dead, with a desiccated brownish color. But as the plant grows taller, up to 60 feet, it completely changes its form of its leaves, and the trunk grows multiple branches forming a lollipop shaped canopy.

The tender green leaves of the mature tree appear similar to eucalyptus leaves, with smooth edges. These tender mature leaves are well above the reach of grazing animals like the giant 12-ft moa bird that roamed New Zealand before human settlement. This rare bird likely drove the evolution of this plant.

Serrated leaves of the immature Pseudopanax ferox (toothed lancewood tree)

Unphotogenic and appearing to be dead, this youngster will change its shape

On the New Zealand trail: mature to the left, juvenile to the right

Native to New Zealand, there are several species of Pseudopanax. They thrive in a moist cool climate. Recently, I had the opportunity to see them in the wild along the trails in New Zealand, and recognized a few different species. Another species, Pseudopanax crassifolius, has leaves with fewer toothed serrations, greener leaves, and red stripes.

This ability to shape-shift as the plant matures is called heteroblastic development. According to Wikipedia the switch from juvenile to mature leaf forms is an age-dependent genetic switch.

Pseudopanax crassifolius (lancewood tree, juvenile leaf)

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