You better can be very careful with eating flowers. The flowers used for garnish are indeed not always edible and some are treated with PESTICIDES!!
Best is not to eat the whole flower but only the petals.
More NON-edible ones: Mistletoe, Lantana, Anemone,Mirabillis, foxgloves, Daffodils, Azalea, Colchicum(winter crocus, Iris, Helleborus, Clematis, buttercup, Oleander, Wisteria but there are many more.