I know not a UK native, but I sowed some crimson clover in my wildflower area last year because much favoured by honey bees (although my bees showed no interest), also because I love the folour. I left the plants to set seed but disappointed that they have not seeded again this year. Is this because UK conditions are not suitable for Mediterranian plants? However, I am wondering if they could have cross pollinated with my native red clover? It seems to me that this year's red clover is a bit different: it stands more upright and more of the leaves are zonal than I remember. But the colour is still red, not crimson.