I use the descriptors established by the International Institute of Phytogenetic Resources for the oca (Oxalis tuberosa) profiles on this site. They define three flower forms: round, starlike, and pentagonal. Here is what each of them looks like:
Round is defined as 75% or greater overlap of the petals.
|Round oca flower|
Starlike is defined as >50% to <75% overlap of the petals.
|Starlike oca flower|
Pentagonal is defined as 25 to 30% overlap of the petals.
|Pentagonal oca flower|
If it seems strange to you that there are undefined gaps between 30 and 50% and between 0 and 25%, join the club. Maybe those degrees of overlap just don’t occur.
Those are all pretty straightforward, but sometimes they make classification difficult. The following picture shows a six-petaled oca flower. I have also seen flowers with seven petals. Some varieties produce frequent double flowers as well.
|This is apparently hexagonal.|
Most appropriately, it is just a variant of the pentagonal type, I suppose.
Oca seeds and tubers are sometimes available in our seed shop.