Abstract: A device for pressure-injecting a tree-treating liquid solution (such as an antibiotic, nutrient, or the like) into the trunk of a tree; the device comprising, essentially, an elongated, precisely tapered nozzle fixed on, and projecting from, a hand-manipulated carrier designed for use to forcefully thrust the nozzle--in effective jam-fitting and sealing relation--into a pre-drilled bore, of predetermined diameter, in the trunk of the tree, and to later remove the nozzle from such bore; the carrier having a passage therein leading at one end to communication with the nozzle, and means being provided to couple such passage at the other end with a source of the liquid solution delivered in metered quantity under pressure.