Blossom from the easy-to-grow butterfly pea plant adds an amazing azure hue to food and drink
Having grown up in southeast Asia, I am perpetually fascinated by which normal, everyday ingredient from my childhood, from goji berries to coconut oil and turmeric, is going to be the next to be suddenly catapulted to luxury status in the west by our hunger for food trends and a good dose of “superfood” marketing. Now it seems there is indeed a new Asian kid on the food trend block and, strangely, it also lives a secret double life as a beautiful and easy-to-grow conservatory plant: the butterfly pea.
If you are looking for a stunning, exotic climber for a warm, bright spot indoors, which also just so happens to provide you with a trendy new ingredient (minus the eye-watering price tag), now is the time to order your seeds.
The butterfly pea or blue pea Clitoria ternatea is a delicate, spindly vine native to southeast Asia. Imagine a sweet pea plant, with leaves and stems shrunk down to half the size, then add the striking, lobed flowers in the most intense of all blues. In Malaysia, Singapore, Thailand and Indonesia, these are used as a traditional food dye. Despite being tasteless, it adds a vibrant azure hue to everything from teas and lemonade-like drinks, to cakes, confectionary and steamed rice.
This is thanks to a group of water-soluble pigments called anthocyanins, the same group of chemicals that give black grapes and blueberries their colour. The shade provided from the leaves, however, is much more intense, so much so that most western visitors I know assume it to be the result of artificial food colouring.
In the age of Instagram, when restaurants live and die by how dazzling their online images are, I have seen the obscure local herb my grandma used to grow popping up on posh London menus and being used to dye everything, from lattes and chia puddings to smoothies, bright blue.
To use it at home, just dry the blossom on a windowsill for a day or two and add them into any water-based liquid, either hot milk, water or cream, or even an alcoholic drink, at room temperature, for them to instantly give up their colour. Curiously, as with many anthocyanins, the colour varies with pH, so you can make a gin and tonic that swirls from peacock blue to bright purple as the acid tonic water hits the flower-infused gin in the glass.
The plants are easy to grow, provided you can submit to their one non-negotiable demand: heat. They need to be kept at at least 20C, but ideally 25C. Trust me, I have tried these outdoors in the UK and they just stop growing – they look perfectly healthy come November, but they are the exact same size they were when I planted them out in May. I sow them in a heated propagator in early March from seeds bought online, and plant them about five to a 30cm pot that I place in the sunniest spot I have indoors, right up against a south-facing window to ensure maximum light. From then on all they need is the support of bamboo canes to climb up and a weekly dose of dilute plant food throughout the summer – and they will reward you with stunning flowers and magic G&Ts come summer.