Answer: Broccoli is a member of the cabbage or cole family. Cole crops are cool weather vegetables, growing best when daytime temperatures are between 65 and 80 F. Warmer temperatures will cause bolting, which is what is happening to your plants. There's no way to stop them from bolting once the process has begun. Cole crops are tolerant of really cool temperatures so starting yours outdoors in March or in September will allow them to grow to maturity without bolting.
Better luck with your next crop!
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