Optimizing marigold (Tagetes erecta L.) petal and pigment yield

African marigold (Tagetes erecta L.) flower pigments can be extracted and used as a natural food additive to color egg yolks orange and poultry skin yellow. Five cultivars were examined for their ability to be grown commercially and mechanically harvested. 'E-1236' was consistently a top producer for three seasons in terms of flower number, flower diameter, plant and flower canopy height, plant stand, and fresh flower, dried flower, and dried petal yield. E-1236 produced the greatest quantity of lutein, a carotenoid pigment, in 1998 (22.0 kg ha(-1)), and E-1236 and 'Orange Lady' both produced the greatest quantities in 1999 (20.7 and 21.3 kg ha(-1), respectively). Transplanted rather than direct-seeded plants produced two more harvests in a single season resulting in greater amounts of lutein production by transplants. In 1998, one mid-season ammonium nitrate application (28 kg ha(-1)) resulted in larger flower diameters with direct-seeded plants but did not affect dried petal yield. Plants were hedge trimmed in 1999 to mimic mechanical harvesting; this resulted in a 45 to 55% reduction in flower harvest data compared with hand-harvested flowers. Of the cultivars tested, Orange Lady produced the greatest quantity of lutein (10.6 kg ha(-1)) when hedge trimmed.