or pre-e·mer·gent

[pree-i-mur-juh nt]
adjective Horticulture.
  1. of or relating to seedlings before they emerge or appear above ground: a preemergent weed-killer.
  1. a preemergence chemical, as a herbicide.

Origin of preemergent

First recorded in 1955–60; pre- + emergent Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018