grass, weeds
稂 centers on unwanted vegetation: grass or weeds that grow where they are not wanted, often in cultivated fields.
稂 combines 禾 (grain) with 良, which likely acts as a phonetic component. The character originally referred to a specific kind of weed that resembles grain, hence the grain radical.
The grain radical 禾 on the left suggests a plant, and the right side 良 looks like a good plant, but together they mean weeds—the unwanted plants that look like grain but are not.
For ロウ, imagine a row of weeds growing among the grain: row -> ロウ, and you need to pull them out.