x1 is a log (fallen/severed trunk) or clipping or cut-flower of/from a plant of species x2, belonging to individual tree (precursor) x3 and leavinf behind remainder/stump/bulb x4.
Typically, this will refer to the main stem of the plant; what is left behind will, therefore, not have notable branches. Thus, a flower which is cut from the branch of rose would not qualify, but a flower cut from a dandelion would. Grass clippings (such as those eaten by a rabbit or those cut and collected while lawnmowing) qualify. May not apply to a plucked or uprooted plant left intact. For "log" specifically, use "ricystanyzilvi'u".