Dandelion
Taraxacum officinale
Why did they choose the dandelion? Even though it has milky sap there is no part of this plant that is toxic (unless it has been poisoned with things like weed killer) (Many plants that have milky sap are toxic.) One can eat:
The leaves are somewhat bitter if picked at the wrong time of the year or the growing conditions are not right. They are best if picked in the cool seasons or if they grow in the shade. They make a nutritious addition to a salad. The salad will taste much better if there are non bitter greens in it too.
The roots are good cooked like carrots. Some peoples favorite way to eat them is to parch and grind them to use instead of coffee. The bitters are thought to make it to be good for liver, gallbladder, spleen and kidney ailments. Because of it's high iron content it is a good blood builder.
Some say the sap will remove warts.
Perhaps that is why the ancient languages called this plant the disorder (tarax) remedy (ac) to make our modern botanical name Taraxacum.
Dining on the Wilds video course has much more information about Dandelions.