Those impossibly blue stars you see on roadside verges in July, carried on wiry zigzagging stems to a metre or more. It is a native British perennial, it makes a deep parsnip-like taproot, and it thrives in poor dry ground where almost nothing else bothers.The blue is as good as blue gets in a British plant. The catch is that you only get it in the morning. Each flower opens at dawn and closes by early afternoon, and every one lasts a single day, so a plant that looks spectacular at nine o'clock can look like a bundle of bare sticks at four. There are plenty of flowers behind it and the display runs June to September, but a visitor arriving after lunch will wonder what you were talking about.It is also frankly untidy. The habit is loose and zigzagging rather than shapely, which reads as authentic in a meadow and as scruffy in a tended border. The first year is a flat rosette of dandelion-like leaves and no flowers; from the second year on it flowers every summer. The young leaves are edible if bitter, and the roasted root is the original coffee substitute.