Growth and flowering of Doritaenopsis queen beer 'Mantefon' as affected by different potting substrates

To assess the growth and flowering of the Doritaenopsis orchid in alternative substrates, Doritaenopsis Queen Beer 'Mantefon' was grown for 15 months in four different substrates; a commercial 100% Chilean sphagnum moss (S), peat moss (P), medium-grade Douglas fir bark mixed with P with a 3:7 ratio (v/v) (BP), and S and P mixes (SP) with a 4:6 ratio (v/v). Physical (porosity and water holding capacity) and chemical (pH and EC) properties of the four substrates were investigated. SP substrate had significantly higher substrate volumetric water content (VWC) than the other three substrates only for the first 3 days after fertigation, and only the BP substrate maintained lower air space than the other substrates. Although there was no relevant growth responses to VWC and air space changes, a better growth in shoots and fastened flowering of Doritaenopsis 'Mantefon' occurred in plants grown in the P substrate, which could be attributed to providing better contact of terrestrial roots to the substrate enabling enough water and nutrient supply, along with a proper pH range of 6.15. At 15 months after transplanting, plants grown in the P and BP substrates had larger leaves and a greater shoot dry weight than the plants grown in the S and SP substrates. Plants grown in the P substrate produced 2.75 flower spikes, whereas the plants grown in the S, BP, and SP substrates produced 2.00 to 2.33 flower spikes. Plants grown in the P, BP, S, and SP substrates produced a third flower spike, being 67%, 33%, 17%, and 8%, respectively. There was no significant difference in the total number of flowers, while the total numbers of buds were 32.3, 23.4, 23.0, and 19.7 in plants grown in the P, S, BP, and SP substrates, respectively. Time to visible flower spike was shortened in plants grown in the P substrate compared to the plants grown in other substrates. With these results, using alternative substrates including peat moss for Doritaenopsis cultivation, growers may be able to promote leaf growth and flower spike induction with lower expenses on substrate costs, resulting in a high quality production of Doritaenopsis 'Mantefon' with more profit.