Frost detector - WORKS.

       "Oca is a common root crop in the southern hemisphere, but is less common here.  Although the tubers are small, they are plentiful and easy to cultivate, requiring very little care once planted.
Oca (Oxalis tuberosa) is a staple crop of the ancient Peruvians as they will grow at high altitude on relatively poor, acidic soils at low temperatures and in high rainfall areas."

       It also mentioned not being frost hardy; elsewhere, it implied using the frosted tops as a clue to harvest.
       T B H this bed was almost fallow this year; sane for these Oca volunteers +  a few missed Garlic.
       You'll maybe see the Oca crop - eventually.