The present invention relates to a method for promoting growth of plants. Particularly, the method of the present invention features overexpression of a calcineurin B-like (CBL) interacting protein kinase15 (CIPK15) having an isoleucine (Ile) residue at position 48 (e.g. a CIPK15 from rice) in plants which can promote growth of the plants. The present invention also relates to a recombinant construct comprising a nucleic acid encoding the CIPK15 operably linked to a promoter. The present invention further relates to a transgenic plant overexpressing the CIPK15 exhibiting improved growth compared to a non-transgenic plant counterpart.