I have about 8 broccoli plants. They were all planted about the same time and were the same size. A few weeks later some have nothing, some have broccoli flowers about the size of a toddlers fist and 2 of them had small broccoli flowers but have now sprouted and grown yellow flowers having gone to seed I presume.

What could cause this difference? Should I chop down the ones with the yellow flowers or is there still hope for them?

Thanks.

I LOVE broccoli that I grow myself! Here's information from Mother Earth News --

Harvesting and Storing Broccoli

Harvest broccoli heads when the florets around the edges of the head begin to show slight loosening, but when the beads in most of the crown are still tight.

Cut the stems at an angle — this will keep water from pooling inside the cut stem and causing rot. Refrigerate the cut heads immediately. To get top home-preserved quality, steam-blanch broccoli before freezing it. Continue to water the plants after harvest, as most varieties will produce secondary heads.

Watch broccoli raab closely, and harvest just as the first flowers show their yellow petals. Sprouting broccoli and broccoli raab are also cut-and-come-again crops that produce a second flush of buds after the first ones have been harvested.

When plants are spaced 18 inches apart, average yields are about 1 pound of broccoli per foot of row. Three to four plants per person is sufficient for fresh summer eating, but you should triple that number if you want a freezer crop for winter.

From How Stuff Works --

Harvesting Broccoli

Time planting to harvest during cold weather. Transplants can be harvested in 40 to 80 days, depending on the variety. Harvesting can continue over a relatively long period. When it is well developed, cut off the central head with five to six inches of stem. Harvest before the head begins to loosen and separate. If small yellow flowers have started to show, it's past the good eating stage.