Abstract Five cultivars of Alstroemeria have been grown in three computer-controlled greenhouse compartments for 3 consecutive years and their flowering response to soil cooling and supplementary lighting has been examined. The following treatment combinations were used: (1) uncooled soil; (2) soil cooling; (3) soil cooling with supplementary lighting. Long days were provided in all treatment combinations from September until December. Plant response to the different treatments was cultivar dependent. Soil cooling (13–15°C) resulted in lower total shoot production for cultivars ‘Annabel’, ‘Mona Lisa’ and ‘Yellow King’, but the percentage of flowering shoots increased in ‘Annabel’, ‘Mona Lisa’ and ‘Red Sunset’. Supplementary lighting had a significant effect on the flowering percentage in ‘Annabel’, ‘Mona Lisa’, ‘Red Sunset’ and ‘Yellow King’. The total number of flowering shoots increased for all cultivars while the number of cymes per inflorescence increased only for ‘Mona Lisa’, ‘Red Sunset’ and ‘Yellow King’.