Forget me not, when you can't forget about it as it is prolific at seeding itself around the garden, once you have it you will never lose it. Although you can restrict the seeding by cutting the flower spikes off as soon as the blooms fade. Even doing this there will still be some seeds escaping. Pesky plant. Of course there new plants can always just be removed and discarded. On the plus side it does provide early colour in the garden in the spring and need little or no attention except when preventing seeding.
Again below the foliage is quite easy to recognise and shows itself well before the end of the season so any unwanted plants can be removed.