Seventy-nine recombinant backcross substitution lines from a cross between Brassica oleracea var. italica and Brassica oleracea var. alboglabra were grown in field trials over five years along with the alboglabra recurrent parent. Plants were scored for the days from sowing to the opening of the first flower, and lines that flowered significantly earlier or later than the recurrent parent were identified. Based on the lengths of the substitutions, evidence for 11 QTL on chromosomes O1, O2, O3, O5 and O9 was found, five of which mapped to similar regions to five of the six found in a previous analysis of doubled haploid lines from the same cross. Several of the QTL were linked closely in repulsion.