In extended use: the treatment of a plant with a beneficial substance. Also concrete: a substance for treating a plant. Obsolete.

= medication, n. 1a 1b.

A protective agent or device; spec. a substance that protects against disease, injury, or pests.

A washing with some liquid for the purpose of producing a particular effect; a liquid preparation used… A liquid preparation used to protect plants…

A substance which protects plants from damage caused by an insecticide or herbicide.