Plant growth retardants for introduction of native Reichardia tingitana

The adaptation of native plants to increase the diversity of marketable ornamental species and to preserve nature has been mainly focused on trees, shrubs and perennial plants, and less so on annual plants. Reichardia tingitana is a native plant of the southeast of the Iberian Peninsula, which produces attractive flowers from March to June. This plant produces stems, which are very tall and sinuous, with one terminal inflorescence. These two last features detract from the plant's use as a bedding plant. The ability of paclobutrazol (PBZ) and ethephon (ETH) to control the growth and development of the aerial part of this plant was investigated. PBZ (0.2, 0.3, 0.4 and 0.5 mg/pot) and ETH (25, 50, 75 and 100 mg/pot) doses were applied as a single soil drench 25 days after transplantation into 11 cm phi plastic pots. The most effective treatments were 0.5 mg/plant for PBZ and 100 mg/plant for ETH, which reduced plant height by 73.1 % and 50.3 %, respectively. PBZ (greater than or equal to0.2 mg) and ETH (greater than or equal to25 mg) significantly reduced plant width, aerial part dry weight, number of flowering stems and number of inflorescences per plant. None of the PBZ doses altered the inflorescence diameter, although all ETH doses reduced this parameter. PBZ (greater than or equal to0.4 mg) and particularly ETH (greater than or equal to50 mg) delayed the beginning of flowering. The results suggested that both PBZ and ETH could well be used to control the stem height of Reichardia tingitana and improve its ornamental value. However, we suggest future studies should look into the effect of time of application on plant height in an attempt to produce compact plants. Such studies will be able to determine the optimal relation between rates, moment of application and desirable plant height.