A method of growing plants in a coherent growth substrate product is provided and includes: providing at least one coherent growth substrate product comprising man-made vitreous fibres (MMVF) bonded with a cured aqueous binder composition; positioning one or more seeds, seedlings, cuttings or plants in contact with the growth substrate product; and irrigating the growth substrate product. The aqueous binder composition prior to curing includes a component (i) in the form of one or more oxidized lignins, a component (ii) in the form of one or more cross-linkers, and a component (iii) in the form of one or more plasticizers.