Thunbergia Alata

I am finding this difficult to answer from the UK, as these are grown as annuals over here. However, my book says to trim it to fit the available space, after flowering if it has flowered on the previous year's growth, or in late winter or early spring if it has flowered on the current year's growth. I do hope that this info. helps you. Maybe it would be a good idea to check with your local Nursery?