Abstract: The effect of mulch and bulb size on the growth of onion was studied using four mulch treatments, viz., non-mulch i.e. control, ridge method of mulch, straw and black polyethylene mulch; and five different sizes of seed bulbs, viz., very small (0.5 g), small (1.0 g), medium (1.5 g), large (2.5 g) and very large (4.5 g). Mulching and bulb size had significant effect on plant height, leaf number, pseudostem diameter, root number and length. The interaction effect of mulch and bulb size was significant in plant height, root length and root number but it was non-significant in leaf number and pseudostem diameter.