Q: I planted my ‘Packman’ broccoli plants on February 22. They are only a foot high but have already gone to seed. I feel cheated!
A: Broccoli plants flower and make seed (bolt) when the young plants are exposed to warm, then cold, then warm temperatures. On February 22 and 23, we had temperatures in the low seventies. The high was thirty eight degrees on March 1 and was seventy eight degrees on March 13. Temperatures since then have rattled around between forty and eighty degrees.
Faced with that rollercoaster ride of highs and lows, your broccoli sensed that spring was coming fast and that they’d better get busy and reproduce.
Try again this fall by starting seed indoors in early August and planting them outdoors in mid September. If it is still hot then, shade the plants with a white sheet. For a spring crop, try planting in a spot that gets morning sun but afternoon shade.