Persian lilac vs bead tree

Persian lilac

noun
  • Syringa × persica, a shrub in the olive family (Oleaceae) 

  • Melia azedarach, a tree in the mahogany family (Meliaceae) 

bead tree

noun
  • Melia azedarach, a deciduous or semi-evergreen tree with poisonous fruit, native to India, Southeast Asia, and northern Australia. 

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