09 December 2009

Gardening Under Glass - The Second of a Runaway Series on My Work Rotation in Indoor Display

Plants of Historic Interest in the Conservatory: Encephalartos woodii

When most people hear that term, their automatic response is, "Gesundheit". No, it's not a nasal condition, or any other kind of condition for that matter. Encephalartos woodii is an important plant in the collection at Longwood. It's a cycad of the family Cycadaceae, ancestors of which were probably munched by dinosaurs.

In LA, Sago Palms - also of the cycad family - are as common as traffic jams on the 405, so when I saw this one in the conservatory my first thought was, "Oh, a cycad", and went on my merry way. Little did I know that I was soon to learn this is no ordinary cycad!

It's called Wood's Cycad after a man named John Medley Wood (1827-1915) who was a curator at the botanic garden in Durban, Africa and who discovered the species in 1895. The solitary clump he found on a steep south-facing slope in KwaZulu-Natal turned out to be the only one in existence. It consisted of 4 stems with a few offsets at the base. One of the offsets collected went to Kew (naturally) with the others being planted at the garden in Durban. Two of the larger trunks were likewise transplanted to Durban in 1907. Sometime between 1907 - 1912, one of the remaining two trunks died and the last one was removed and sent to Pretoria in 1916. Since the only known plants of this species are now in cultivation and none have been found in the wild, it is considered extinct in nature.

Here's the other fascinating tid-bit: this cycad is dioecious (totally, dude) meaning there are separate male and female plants. The plants in existence today are all male. No females are to be found anywhere. This means that asexual propagation is the only way to reproduce this plant.

Now, I know what you're thinking. You're thinking those darn botanists should have left well enough alone and not removed the plant from the wild and just let it do it's thing, pop out some pups and make more plants the way nature intended. In this day of sustainability and preservation, environmental groups would have lobbied and protested and that likely would have been the case. It would also be likely that within a short period of time the plant would be completely extinct. So, moving it to cultivation probably saved it.

Isn't that splendid!?

So how many are there now, you ask? In over 100 years of propagating this plant by pups, those whose job it is to guess, estimate only about 500 plants are believed to exist in botanic gardens and private collections around the world.

Some mad plant scientists out there are playing around with tissue culture in the hopes of producing a female, but this is tricky. Remember, this plant was probably around when the dinosaurs roamed and since every offspring in the world now is a clone of the original one found in the wild, there are innumerable potential infections or diseases that could be affecting the tissue and in order for this method of propagation to be successful you must use sterile tissue.

Good luck with that, I say.

Some other lab-type people decided to try a more natural route and have begun to cross E. woodii with its closest known relative, E. natalensis. The thought here is that the hybrid generation will be 50% E. woodii. A female hybrid would be pollinated with pollen from the E. woodii to produce a second generation hybrid that is 75% E. woodii. The hope is that within five generations, they will have a plant that is genetically 97% pure E. woodii.

The plant here at Longwood was accessioned in 1969 and was acquired by the garden's first director, Dr. Russell J. Seibert (who was the director of the LA Arboretum from 1950 - 1955; what a coinkydink!), following his trip to Africa in 1963. It's believed the offset still growing here at Longwood was from the original plant brought in from the wild. There is an infamous story that some years ago, a student was sent to clean the dead fronds from the plant and succeeded in removing all the pups that had been produced, thus eliminating the immediate opportunity to propagate this plant and increase Longwood's collection. Consequently, most students are afraid to go near it!

The cones - called strobili - on this thing are massive, potentially reaching a good 47" long and 10" in diameter. Late last week one of the cones got too heavy and snapped. The broken piece was carefully removed from the nest of foliage and saved for teaching purposes.

Each of the scales, or structures composing the cones, contain the sporangia which in turn contain the spores or what those who don't give a hoot about botanical accuracy might call pollen. The lower surface looks like a sponge, with lots of tiny pores. If you were to snap one off and shake it - as I did - you'll see the yellowish powder float out.

The end of the cone where the break occurred looked like a sunflower, with all the scales arranged spirally around the axis.

You have to admit, it's pretty cool.

The lesson I took away from the bit of research I did was that sometimes extreme measures are required to save a species from extinction and that someone needs to run, not walk, over to Guest Services and get thee some signage so that the people who casually wander by this amazing plant will be able to read its history.
Lucky you, because next time you're over in the conservatory admiring this rare cycad you can stop someone and ask them if they know how unique the Encephalartos woodii is. Just don't be surprised if they hand you a Kleenex!

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