What about the bolting of the spring onions sown in autumn?

It means it's mature. It blossoms and bears fruit.

The main reasons for the early bolting of shallots are that the seeds or seedlings of shallots have passed vernalization at low temperature, the seeds are stored for too long, the seeds are sown too early in early spring, and the plants are weakened by extensive management and high temperature and drought, which will all lead to the early bolting of shallots. Therefore, strengthening this measure can effectively prevent the early bolting, flowering and fruiting of shallots, and improve the quality of shallots.