The late-flowering phenotype of mutations in the LUMINIDEPENDENS (LD) gene and the late flowering caused by the naturally occurring dominant gene FRIGIDA (FRI) are suppressed in the Landsberg erecta (Ler) strain of Arabidopsis thaliana. This suppression is dependent on a locus on chromosome 5 designated FLC. Of the ecotypes tested, only the Ler strain contains the suppressor allele of FLC; ld mutations and FRI cause late flowering in the other genetic backgrounds. The allele at FLC also has a moderate effect on flowering time in the absence of FRI or ld mutations. The flowering time effects of FLC are gene dosage dependent.