Peas had been shown to be true-breeding (all offspring will have the same characteristic generation after generation).
Peas exhibit a variety of contrasting traits (purple vs. white flowers; round vs. wrinkled seeds).
The shape of the pea flower protected it from foreign pollen. Peas usually reproduce by self-pollination, in which pollen produced by a flower fertilizes eggs in the same flower.
Pea plants grow quickly and do not require much space.