a disposable dispensing capsule for a plant injectable liquid composition includes a flexible cap hermetically sealed to a receptacle . the capsule is pressurized when the cap is forcibly flexed inwardly . in one embodiment flexure and thereby pressurization are maintained by an interference fit between a spindle in the receptacle and a socket depending downwardly from the cap central portion . in another embodiment flexure is maintained by engagement of hook - shaped posts in the receptacle with a lip in a collar depending downwardly from the cap central portion .