heliotrope vs perennial

heliotrope

noun
  • A plant that turns so that it faces the sun. 

  • A light purple or violet colour. 

  • Particularly, a purple-flowered plant of the species Heliotropium arborescens. 

  • A bloodstone (a variety of quartz). 

  • An instrument, employed in triangulation, that uses a mirror to reflect sunlight toward another, very distant, surveyor. 

  • The fragrance of heliotrope flowers. 

adj
  • Light purple or violet. 

  • Keeping one’s face turned toward the sun. 

perennial

noun
  • A plant that is active throughout the year, or has a life cycle of more than two growing seasons. 

  • A thing that lasts forever. 

  • A person or thing (such as a problem) that appears or returns regularly. 

adj
  • Lasting or remaining active throughout the year, or all the time. 

  • Appearing or recurring again and again; recurrent. 

  • Continuing without cessation or intermission for several years, or for an undetermined or infinite period; neverending or never failing; perpetual, unceasing. 

  • Of a plant: active throughout the year, or having a life cycle of more than two growing seasons. 

  • Appearing again each year; annual. 

How often have the words heliotrope and perennial occurred in a corpus of books? (source: Google Ngram Viewer )