N-(2-Chloro-4-pyridyl)ureas represented by the formula (I): ##STR1## wherein R.sub.1 represents hydrogen or alkyl, R.sub.2 represents an aromatic group, especially phenyl, which may be substituted by alkyl, alkoxyl, hydroxyl or halogen, and X is oxygen or sulfur, and acid addition salts thereof, useful as plant growth regulators, are disclosed. Method of making and using same and agricultural compositions thereof are also disclosed.