flowers of Castanospermum australe, photo by Geoff Stein, in Plantfiles, thanks Geoff
It's not often that I have to look twice at a potted plant in the grocery store. Same old, same old: Chinese evergreen, pothos, Dracaena, african violet....there is rarely a surprise among the disposable seasonal potted plants. The best I can hope for is a new cultivar of one of those standbys, or a plant marked for clearance but still on this side of the brink of compost. But one day as I idled in the checkout line, I saw a plant that I wasn't even sure was real.
"Pardon me, lady. You go ahead, I'm looking at this plant"
A two inch pot, and a stem sprouting from a bean — an oversized, preschooler's plastic play bean. It was green throughout, like no bean I'd ever seen. Actually, it looked like an avocado seed but weirdly green. The plant's leaves were clearly not avocado. I had to touch it to convince myself it was a real bean. And tug on the plant to believe it actually arose from the bean. Ok, it was real.
The tag said Lucky Bean Plant. Yeah, right. Probably in the same family as Lucky Bamboo (not really bamboo) and Lucky Nut (highly toxic!) and Siamese Lucky Plant (a lucky and exotic name, a marketing double whammy.) In a rare moment of self-restraint, I left the plant on the shelf, checked out, and went home to research the green oddity. A few keystrokes and clicks yielded a list of candidates: Saint Thomas bean vine, castor bean...aha, lucky bean, Castanospermum australe.
Yes, the bean is real. I imagined that a bean that big can only come from a tree, and this one does. It is known in its home country, Australia, as Moreton Bay Chestnut or black bean tree. C. australe is a tropical tree in the "bean and pea" (legume, Fabaceae) family, cousin to chickpeas and kin to kidney beans. That makes it also a relative of redbud, a tree familiar to many gardeners. As redbud bears clusters of flowers directly on its branches, so does Moreton Bay chestnut. The spring flowers (April in America, October in Australia) are tropically bright, a combo of red and yellow in each floret. Remarkably, it is the only species in its genus.
Moreton Bay Chestnut is used in tropical landscapes. Florida gardeners might plant this species, and have likely seen it used locally. This medium sized tree has attractive, dark green, glossy leaves on spreading branches. Admirers who step under the branches can view the vibrant blooms in spring, or the many creatures who visit the blossoms to drink their nectar. After the flowers fade, large pods develop. Each pod bears up to five of the nearly-golf-ball size seeds. Mojca Debevec, writing for the Australian National Botanic Gardens, says this tree has a strong root system; that indicates usefulness on banks, but could be problematic around hardscaping. Another mild caution is that the seeds (bean, nuts) contain toxic saponins. Aboriginal peoples used the nuts by processing them first, but fresh seeds could sicken animals or fish.
But back to that bizarre little plant...
The few Lucky Bean plants that I saw have long since gone home to lucky owners. I've been unable to find the plant at our local nurseries. Eldon Tropicals has Moreton Bay Chestnut listed in their tree selection. The plant is "available but currently unavailable," (whatever that means) at Amazon.com. My Aussie readers, if I have any, may find this plant easy to obtain.
Gardeners and visitors in Florida and southern California might look for mature trees nearby, and collect a few nuts. Plant the nuts in well draining potting mix. The green nut splits in the middle as does an avocado pit. Young Lucky Bean plants like steady moisture, rich but well draining potting mix, and bright light. The young tree can be kept for many years as a potted specimen. With excellent care, this potted curiosity from the grocery store might some day become the flowering tropical tree- if you are lucky.
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Australian National Botanic Garden, http://www.anbg.gov.au/gnp/interns-2002/castanospermum-australe.html , accessed 3-13-13
Eldon Tropicals, http://www.eldontropicals.com/TREES.html , accessed 3-13-13