Ill weeds grow apace.

Harmful tendencies, bad habits, or troublesome people may spread and strengthen quickly when nothing checks them. The image contrasts the vigor of unwanted weeds with the effort usually needed to cultivate desirable growth.

The saying is often used as a cynical warning that what is damaging or undesirable can flourish with alarming ease. It can also express frustration when misconduct or disorder seems to multiply faster than remedies or improvements.

Use it figuratively when undesirable behavior, problems, or influences are rapidly increasing. Its gardening metaphor gives the remark a proverbial, mildly condemnatory tone; avoid applying it to people, as calling people “weeds” can sound dehumanizing or needlessly harsh.