Friday, 4 May 2012

What is this plant with beans called?

It's just down the street, on the corner, and I walk past it every day. In early springtime there is a flood of yellow flowers. These have now mostly morphed into these bean-like pods hanging off the plant. A few of the flowers remain, but most of them were pollinated by insects, probably bees, and have turned into pods full of seeds.

The reason I took this photo is not just to find out what the plant is called. It's also because of the recent story about the vanilla bean market, which is unhealthy globally giving Australian vanilla growers opportunities to make some extra money. I wrote about vanilla in 2010 through a contact at the University of Western Sydney and so I keep an eye open for stories about this strange pod.

Just growing the beans themselves is a challenge, especially at pollination. Vanilla is an orchid and commercial vanilla is pollinated manually. In their native Mexico, vanilla flowers can be pollinated by a bee of the Melapona family, but the main countries producing vanilla are Madagascar and India. Regular European honey bees cannot negotiate the vanilla flower's complex shape. Getting vanilla flowers to produce beans is a fraught process.

When stressed, which can be done by withholding water from the vanilla vine, racemes emerge in the axils at the base of the leaves. Each raceme produces 15 to 30 flowers and if they are not pollinated immediately the flowers die. Every day only one flower opens on the raceme. Fussy flowers!

But the yellow flowers down the street from my place are not fussy at all and respond plentifully to the ministrations of regular European honey bees. The pods emerge well before summer. No doubt vanilla growers would love it if their plants were as easy to make fruit as this one. Do you know what it is?

[UPDATE 4.25pm:] It's a weed called Easter cassia.

2 comments:

Cathy Clarke said...

Did you get a response on the name of this plant? I have the same plant at my unit and need to find out the name. Phil (cpclarke@gmail.com)

Princeshwy said...

I have one yoo I want to know if I can eat it