58:4 The bracha over fragrant grasses and plants is “Borei isvei vesamim,” that G-d created fragrant grasses. (Here, the Kitzur Shulchan Aruch has a grammatical note explaining the pronunciation of the words in this bracha.) The difference between a tree and a plant for our purposes is that a tree is perennial, produces leaves, and has a firm stem. If the stem is soft, the bracha is “isvei vesamim.”
58:5 The bracha on something fragrant that is from neither a tree nor a plant, such as musk, is “Borei minei besamim,” that G-d created different types of fragrant things. The Kitzur Shulchan Aruch expresses an opinion that this would be the appropriate bracha to recite over aromatic dried mushrooms.