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  Eur.J.Hortic.Sci. 80 (2) 87-93 | DOI: 10.17660/eJHS.2015/80.2.7
ISSN 1611-4426 print and 1611-4434 online | © ISHS 2015 | European Journal of Horticultural Science | Original article

Effect of paclobutrazol in potted plants of four cultivars of Dianthus barbatus × chinensis

A. Lenzi, M. Nannicini, P. Mazzeo and A. Baldi
Department of Agrifood Production and Environmental Sciences (DISPAA), University of Florence, Italy

Dianthus barbatus × chinensis is a perennial herb derived from the interspecific cross between Sweet Williams (D. barbatus L.) and China pink (D. chinensis L.). At present cultivated as a cut flower, it could be potential as a flowering potted plant, but height control should be performed. In this study, the possibility to reduce plant height by the use of paclobutrazol (triazole; PBZ) was investigated in four cultivars. In addition, the effect of PBZ on flowering (inflorescence number and size, and flowering time) and on leaf colour was evaluated. Two experiments were carried out in different seasons (corresponding to autumn potting and summer potting, respectively) and PBZ was applied as a substrate drench at different dosages: 0.5, 1, and 2 mg per pot for autumn-potted plants; 0.25, 0.5, and 1 mg per pot for summer-potted plants. Paclobutrazol resulted to be effective in controlling plant height in all the studied cultivars without producing any toxicity symptoms. Neither effect of PBZ on number and size of inflorescences, nor on flowering time was observed. On the contrary, PBZ enhanced leaf colour.

Keywords Dianthus spp., flowering pot plant, leaf SPAD, PBZ, plant growth retardant, plant height control

Significance of this study

What is already known on this subject?

  • It was previously demonstrated that PBZ is effective in controlling plant height and enhancing colour of a large number of floriculture crops. However, different species have their own needs as to way of application (spray or substrate drench) and appropriate dosage.
What are the new findings?
  • The study showed that PBZ as a substrate drench reduces plant height and enhances foliage colour in potted Dianthus barbatus × chinensis, a species at present cultivated as a cut flower. Appropriate dosage ranges from 0.5 to 1 mg a.i. per pot depending on pot size, cultivar and season.
What is the expected impact on horticulture?
  • The ornamental plant market is characterized by being eager for novelties. Therefore, the use of Dianthus barbatus × chinensis as a new flowering pot crop, which is made possible by height control, may represent an opportunity for growers.

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Received: 10 July 2014 | Revised: 14 October 2014 | Accepted: 18 November 2014 | Published: 22 April 2015 | Available online: 22 April 2015

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