EFFECT OF CULTIVAR, TIMING, GROWTH RETARDANTS, POTTING TYPE ON POTTED SUNFLOWERS PRODUCTION

Abstract

Flowering pot plants represent one of the most interesting and promising typologies of ornamental productions, and frequently new species or products are selected for marketing. The use of sunflower as flowering pot plant, thought quite unusual for this species, could represent a powerful innovation, also in view of the positive trend shown in the last years by the production of sunflower as cut flower. On the other hand, as for any new product, there is a lack of information about the cultivation technique and the appropriate technology for getting best results in producing high quality potted sunflower. The aim of this work was to expand our knowledge on the cultural requirements of Helianthus annuus L. when grown as flowering pot plant and to characterise four genotypes (‘Big Smile’, ‘Pacino’, ‘Sunspot’ and ‘Teddy Bear’) selected for pot cultivation, by evaluating growth and ornamental parameters. We investigated the effect of different sowing periods (early spring, mid spring, late spring), container size (12 or 16 cm diameter), product typology (single or multiple plant per pot) and growth retardants (paclobutrazol and flurprimidol) on plant height and diameter, and on blooming period and ornamental characteristics of the flower. Results have shown that early sowing induces precocious blooming and reduced plant size in all tested genotypes with respect to late sowing date. Also container size affected plant growth, in particular plants grown in larger pots showed more compact habitus and a slight earliness in blooming. Growing multiple plants per pot resulted in a reduced size of each single plant, but the aesthetic value of the whole pot was increased. Our experiments indicated that the four genotypes tested, gave best results if treated with growth retardants which not only reduce plant height, but also increase plant uniformity. Between the two compounds tested, pacrobutrazol (used as a soil drench) was more effective then flurprimidol (used as foliar spray) in reducing size, without negative effects on crop quality.