Abstract
Roses are increasingly being grown in soilless systems to increase productivity and reduce the challenges associated with soil-based cultivation. This study investigates the effects of using cocopeat and volcanic tuff substrates, the particle size of tuff, and substrate depth on the growth and flower quality of roses (Rosa hybrida L. cv. top secret) grown under greenhouse conditions. The treatments were cocopeat, tuff, cocopeat-tuff mixture, and tuff of particle size of 2 to 4 mm, 0 to 4 mm, and 0 to 8 mm at depths of 20 cm and 40 cm. The results showed that cocopeat had the highest water-holding capacity and photosynthetic rate. Tuff substrates had higher chlorophyll content throughout the growing season. Although flower numbers per plant in cocopeat and tuff from 0 to 8 mm at a depth of 20 cm were statistically similar, tuff from 0 to 8 mm had longer flowering stems and larger post-harvest flower diameters than cocopeat. An increase in the tuff depth from 20 to 40 cm decreased the flower number and main stem diameter. In conclusion, while cocopeat promotes rapid initial growth, volcanic tuff substrates, particularly tuff from 0 to 8 mm at a depth of 20 cm, provide long-term benefits for flower quality and plant health.