You will first notice the large floret....then when it starts to slightly move into seperated florets it is time.......they should be ready now..........don't wait for yellow pieces and then yellow flowers as the taste changes.................cut the florets on a SLANT on the stem....leave as much stem on a slant as possible as the stem will produce smaller but still delicious floret pieces of broccoli not as big as the first head..........do not take them into the house yet.....................have a big clean bucket or hugh metal pot filled with ice cold water and 1/2 salt..................have the water filled up to the top you can do this outside on the cement or driveway as when I did this to super clean them hundreds of tiny black bugs came rushing out and going over the side of the container as they don't like the cold water and salt...............I did this mix one more time....................and then rinsed it well again with very cold water..........then I took them apart.............and checked each one just incase..........I am suspecting our cauliflower also is going to have this same problem If you don't have salt.................a little white vinegar would also work..............but you have to rinse several times to get this out. This vinegar method withcold water can be used for store bought lettuce to prevent illness. must rinse several times
