I moved to India a few years back and started a small community farm. Planted broccoli 4 weeks ago. Plants have grown about 12 in tall and look very healthy, yet no florets have shown up. Temp here is around 72F/45F and we have been irrigating regularly. We are only using organic fertilizers – cow dung manure and humus.
We had great broccoli harvest a couple of years ago, then it faded a bit last year, and nothing yet this year.
Our Cauliflower crop has also failed – most of the plants have prematurely flowered sparsely and seeding…. very disheartening.
Broccoli and cauliflower sometimes do not form flower heads when the soil is too rich in nitrogen. Compost the cow dung before you use it or do not use manure at all–use instead well-aged compost that contains no manure. Manure is very rich in nitrogen. Other reasons for flower heads not to form would be cold temperatures (do not plant too early when temperatures are below 50F), water stress–too much or too little, and weed competition.