Euphorbia marginata vs snow-on-the-mountain

Euphorbia marginata

snow-on-the-mountain

noun

  • A small shrub in the family Euphorbiaceae, having white-margined leaves and white flowers; Euphorbia marginata. 

How often have the words Euphorbia marginata and snow-on-the-mountain occurred in a corpus of books? (source: Google Ngram Viewer )