grass tree vs tree heath

grass tree

noun
  • A New Zealand shrub of the genus Dracophyllum, that grows up to 12 m high and found throughout in drier climates and at higher altitudes, with slender erect or spreading branches. Rigid, leathery grass-like leaves are usually crowded towards the tip of the branchlets. Also called spiderwood. 

  • Dasylirion longissimum (family Asparagaceae, Mexican grass tree) 

  • Richea pandanifolia (family Ericaceae, giant grass tree). 

  • Any of various small trees of the family Xanthorrhoeaceae (especially of the genus Xanthorrhoea), having a thick trunk crowned with a dense tuft of pendulous, grass-like leaves. 

  • Dracophyllum (family Ericaceae), a genus of about 100 species. 

tree heath

noun
  • Dracophyllum arboreum (Chatham tree heath) 

  • The flowering plant Erica arborea, native to east Africa and the Mediterranean. 

  • Erica scoparia (green heath, besom heath, broom heath) 

  • especially Trochocarpa laurina of Australia and New Zealand. 

  • Other plants of genus Erica of similar habit 

  • Ecological domains characterized by large numbers of such species of ericaceous plants. 

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