The 4th of July cutoff date is not because of any danger of poisoning. The eight to ten weeks of harvesting has passed and the plant now needs to feed the roots and prepare for next years production. The quality of the stalks usually has deteriorated as well but are not dangerous. The flower stalks have no effect on the plants edibility. They are removed so the plant can use its energy to produce stalks instead of seeds.
The 4th of July cutoff date is not because of any danger of poisoning. The eight to ten weeks of harvesting has passed and the plant now needs to feed the roots and prepare for next years production. The quality of the stalks usually has deteriorated as well but are not dangerous. The flower stalks have no effect on the plants edibility. They are removed so the plant can use its energy to produce stalks instead of seeds.