Blue Pea Green
Made with the flowers of the Clitorea ternatea
Our handmade watercolours are all available on our Etsy store.
This may be a more familiar plant to people, as the flowers of the blue pea vine are popular as a source of blue food colouring! There is a hawker store at Marine Parade Food Centre that we sometimes visit, that sells delicious nasi lemak served with blue rice grains dyed with this plant. But the lemak of the rice comes from the addition of coconut milk, as the flowers do not impart a taste.
We have quite a few of these vines growing around our studio garden. Since it is a climber, it requires a fence to support the twirly branches, extending into areas with more sunlight. An interesting fact about this plant is that it is a type of legume that has the capability to form root nodules (spot them in the picture on the left!), in which certain bacteria in the soil works with it to “fix” nitrogen from the air into a more accessible form. When mulched back into soil, it should help make the soil more fertile to support other plants.
It may be surprising that the pigments from this plant comes out green instead of the characteristic blue. It is because during the pigment extraction process, we use an alkali which shifts the colour towards a green. The blue pea colour is sensitive to pH changes; adding a little lemon juice on the ink turns it into a bright pink, whereas with baking soda it will become a teal green. When blended with a pinch of indigo blue, the blue pea green gives a deeper, more luscious green that is reminiscent of green leaves in a forest.
