2017 ASHS Annual Conference

Tagetes patula (marigold) is a beautiful ornamental plant with fine-textured, dark green foliage and yellow, orange, or bicolored flowers. The relative salt tolerance of eight marigold cultivars (‘Hot Pak Orange’, ‘Hot Pak Yellow’, ‘Hot Pak Gold’, ‘Taishan Orange’, ‘Taishan Yellow’, ‘Taishan Gold’, ‘Discovery Orange’, and ‘Discovery Yellow’) was evaluated in a greenhouse experiment. Plants were irrigated weekly with nutrient solution at electrical conductivity (EC) of 1.2 dS∙m^-1 (control) or saline solutions at EC of 3.0 or 6.0 dS∙m^-1 (EC 3 or EC 6). Marigold plants began to show foliar salt damage (leaf edge burn, necrosis) at six weeks after treatment. At harvest (eight weeks after treatment), ‘Hot Pak Gold’, ‘Hot Pak Yellow’, and ‘Taishan Orange’ plants in EC 6 all died, and the remaining five cultivars experienced severe foliar salt damage with visual score less than 2 (a scale of 0 to 5, with 0 = dead and 5 = excellent with no foliar damage). In EC 3, ‘Taishan Gold’ and ‘Taishan Orange’ plants showed moderate foliar damage with a visual score of 2.3 and 2.1, respectively, whereas the remaining six cultivars had slight or minimal foliar salt damage with visual scores around 4. Treatment EC 3 reduced the flower number of ‘Discovery Orange’, ‘Discovery Yellow’, ‘Hot Pak Gold’, and ‘Hot Pak Yellow’ by 53%, 29%, 50%, and 31%, respectively; whereas EC 6 decreased the flower number of ‘Discovery Orange’, ‘Discovery Yellow’, and ‘Hot Pak Yellow’ by 46%, 51%, and 53%, respectively. Saline solutions slightly reduced the flower number of ‘Hot Pak Orange’, ‘Taishan Gold’, ‘Taishan Orange’, and ‘Taishan Yellow’. In addition, both EC 3 and EC 6 did not reduce the shoot dry weight of all cultivars except ‘Hot Pak Yellow’. In summary, all marigold cultivars are moderately sensitive to salt.