Effects of peat moss, cocopeat and licorice residues on geranium growth characteristics (Pelargonium × hortorum ‘Ringo 2000 Deep Red’)

Geranium is one of the most important potted and bedding ornamental plants that selection and construction of a suitable growing medium is important for success in any stage of its production. In order to determine a suitable pot mixture for geranium, the effect of peat moss, cocopeat and licorice root residue in soil-based mixtures (50% by volume, including soil and perlite in a ratio of 5:2), an experiment with 6 treatments (50% by volume) including peat moss (P50), cocopeat (C50), licorice root residue (L50), peat + cocopeat (P25C25), peat + licorice residue (P25L25) and cocopeat + licorice residue (C25L25) was performed. The results showed that the highest values of plant height, shoot fresh weight, shoot dry weight, number of leaves, average leaf area, number of inflorescences, petiole length and apparent quality rating were belonged to P50 treatment. The highest values of root fresh and dry weight  and root volume were obtained in P25C25 mixture. The highest leaf area ratio (LAR) and relative leaf water content (RWC) were belonged to P50 treatment and the highest amount of chlorophyll was belonged to P25L25 mixture. In general, the best vegetative and flowering performance of plants were observed in P50 treatment (containing loamy soil (35%), perlite (15%) and peat moss (50%)) and then in P25C25 treatment. Therefore, with little access to peat moss, less than 50% of peat moss can be replaced with cocopeat, and more cocopeat has a negative effect on plant growth. Licorice residue had a negative effect on most of the measured indices.