This is controlled by two recessive genes, fn, and fna.
They are interactive -fn or fna alone gives two flowers, fn fna together gives two or more flowers. However, the genes may be incompletely expressed; flower number is also influenced by environmental conditions.
|#1836, a tall multiflowered pea from Greece, showing repeated double flowering nodes|
It would be nice to get both fn and fna - I will probably need to cross a number of multiflowered lines to see if I have both genes...