Hi Miss Dewi...Anything, plant or animal, that is prolific reproduces well with a great many offspring! I think you're correct about heirloom plants. As far as I know they are plants that are true varieties, that have existed for a long time and have not been altered by breeding them to other plants etc. Lots of people are working hard to save plants that are original to an area but which have fallen out of favor because the hybrid plants are more disease resistant, "prolific" and otherwise desirable to gardeners. I'm sure someone else can add information to this discussion. SandyO CH #1146 of the moderate persuasion, old as dirt and somewhat of an heirloom