The Collaborative International Dictionary
Phytogeography \Phy`to*ge*og"ra*phy\, n. [Phyto- + geography.] The geographical distribution of plants.
Wiktionary
n. (context biology English) The science that studies the geographical distribution of plants; geobotany
Wikipedia
Phytogeography (from Greek φυτό, phyto = plant and γεωγραφία, "geography" meaning also distribution) or botanical geography is the branch of biogeography that is concerned with the geographic distribution of plant species and their influence on the earth's surface. Phytogeography is concerned with all aspects of plant distribution, from the controls on the distribution of individual species ranges (at both large and small scales, see species distribution) to the factors that govern the composition of entire communities and floras. Geobotany, by contrast, focuses on the geographic space's influence on plants.