Red sky at night, it’s coriander time. Mine has come up from seeds from coriander I grew in Spring. You can sow it direct in the soil or in pots and transplant it. Pots give it a bit more protection from slugs and snails which seem to like it. I think of it as the fresh herb alternative to basil when the first frosts come and turn the basil plants brown overnight. Don’t be disheartened if you’ve had nothing but flowers from your coriander, it’s a timing thing.