I once planted some blue poppy seeds in a pot. One seeding came up. It definitely wasn't a poppy. Someone who knew more than me, (which includes most people), said it was a chive ...
In reply to Billysdad:
Never mind. With planting seedlings Sometimes it can be easyer to plant seeds and seedlings in a particular spot
with me cause I plant wildflower seeds I have to try to keep an eye on what seedlings are and arnt from the seed iv down cause wild plants can come up anywhere even near spots you plant a particular seed or even a seedling for that matter and try to keep other wild seedlings away from the spot I planted a seedling and re plant it away from the spot. when the seed you planted in that exact spot germinates and grows into a young seedling you can watch it grow.
Sometimes it can help to know what the seed looks like for example cornflower seedlings look different to Sunflower seeds and cowslip. And if you see a seedling Germanate out of the seed and it’s the same seed you planted and in the same spot you planted it that can be helpful if you want to know if the seedling is from the seed you planted or is a different seedling.