The Study of Plant Selection and Application on Indirect Green Facade in Taipei City
Date Issued
2015
Date
2015
Author(s)
Hung, Pei-Rong
Abstract
This study aims to select plant species that adapt well to urban environments in Taiwan for use on indirect green façade and develop relevant techniques in the installation of indirect green facade. Preliminary study was conducted to survey existing green facades in Taipei for the plant status and problems observed with solutions recommended. In addition, selections of plants for use on an indirect green façade were made based on plant adaptability to light and requirements for supporting device. Finally, effects of fertilization frequency on plant growth on an indirect green façade were investigated. Twenty-one green facades in Taipei were surveyed for plant species used, growth status, growing conditions, construction methods, and substrate conditions. The results were presented in three groups based on overall scores for aesthetic effects: Excellent (>80), fair (60-80), poor (<60). Twelve species including Ficus vaccinioides Hemsl. ex King, Schefflera arboricola ‘Trinette’, Asparagus densiflorus (Kunth) Jessop, Nephrolepis exaltata, Syzygium buxifolium Hook. et Arn., Syrgonium podophyllum schott., Rhoeo spathacea Stearn., Codiaeum variegatum Bl., Dracaena marginata Lam. ‘tricolor’, Terminalia catappa L., Ipomoea digitata L., and Ficus pumila L. received an excellent score. Five species including Dracaena reflexa Lam. ‘Variegata’, Duranta erect L., Setcreasea purpurea Boom., Pogostemon cablin (Blanco) Benth. ‘Variegata’, and Clerodendrum ×speciosum received a fair score. Five species including, Stromanthe sanguinea Sond. ‘Tricolor’, Dregea volubilis (L. f.) Benth., and Lonicera japonica Thunb. received a poor score. Some common problems seen in green façade include poor plant adaptability, insufficient light at the upper level due to rain shelter, and unacceptably low soil EC. Most green façades face the problems of lower soil EC and media water content at the upper level than the lower level. For the study of green façade plant adaptability to light, 5 tested plants were grown on the sunny side (236.8 µmol·m^-2·s^-1 with 100% transmittance) and shady side (53.5µmol·m^-2·s^-1with 23% transmittance) of façade. The results showed that Thunbergia grandiflora Roxb., Clerodendrum ×speciosum and Pyrostegia venusta (Ker-Gawl) Miers adapt well to high light while Passiflora edulis Sims. showed some potential. Thunbergia grandiflora Roxb. grew vigorously with leaf reacting prominently to light which yielded outstanding visual effect. Clerodendrum ×speciosum and Pyrostegia venusta (Ker-Gawl) Miers showed moderate growth with leaf reacting less prominently to light; these plants had fast coverage which helped to enhance the visual effect. Thunbergia grandiflora Roxb. also grew well under shady conditions whereas Clerodendrum ×speciosum and Pyrostegia venusta (Ker-Gawl) Miers had some potential. Trachelospermum asiaticum Nakai ‘Tricolor’grew slowly with sluggish reaction to light making it unable to cling to supporting mesh and resulted in poor coverage, thus was not suggested for use in indirect green façade. When using plants with decent potential, increasing plant number along with proper grooming and pruning and regular maintenance can increase coverage and enhance ornamental effect. In terms of requirement for supporting device, tested plants Passiflora edulis Sims., Pyrostegia venusta (Ker-Gawl) Miers (Tendrillar plant), Thunbergia grandiflora Roxb., Clerodendrum ×speciosum, Clitoria ternatea L. and Tristellateia australasiae A. Richard (Twiner) were allowed to climb up 4.5 cm、6.5 cm、8 cm and 12.5 cm mesh. The results indicated that tendrillar climbers are more sensitive to mesh size as shown in Passiflora edulis Sims. where the plant grew faster as the mesh size increased. Pyrostegia venusta (Ker-Gawl) Miers prefers smaller mesh as it exhibited fast growth when first planted. Thunbergia grandiflora Roxb., Clerodendrum ×speciosum, Clitoria ternatea L., and Tristellateia australasiae A. Richard showed no significant difference in growth rate and coverage when planted on the façade with four different mesh sizes. After evaluating the ornamental and visual effects, plant growth and physiological state of the six climbers, 6.5 cm mesh was found to be the most versatile. To find an optimal fertilization schedule, Thunbergia grandiflora Roxb. and Clerodendrum thomsoniae Balf. f. were planted in the winter with 100% transmittance and in the spring with 23% transmittance. Fertilizers used in the study were Peters Solution 20N-8.8P-16.6K and slow-release 13N-4.8P-10.8K Hi-Control S101. Four treatments and a control (no fertilization) were carried out. In HC treatment, 25 g/pot Hi-Control was applied quarterly. In HC+1P treatment, 25 g/pot Hi-Control was applied quarterly with 2000 mg L^-1Peters applied once weekly (500 mL/pot). In HC+2P treatment, 25 g/pot Hi-Control was applied quarterly with 2000 mg L^ -1 Peters applied twice weekly (500 mL/pot). The results showed that Thunbergia grandiflora Roxb. in the control group had stunted growth. HP+1P treatment promoted fast growth and coverage and showed some flowering with excellent ornamental effect. Subsequent fertilization was switched to HC treatment to maintain quality of the façade. Clerodendrum thomsoniae Balf. f. without fertilization (control) underperformed in growth, but some ornamental effect was evident nevertheless. HC+2P resulted in the best growth and ornamental effect for Clerodendrum thomsoniae Balf. f. with subsequent fertilization switched to HC to lower the cost of maintenance. To sum up above studies, when installing a three-dimensional green façade, the whole visual effect is affected by plant characteristics, lighting conditions, media, and maintenance management. In Taipei, when selecting plant species for indirect green façade, Thunbergia grandiflora Roxb., Clerodendrum ×speciosum, and Pyrostegia venusta (Ker-Gawl) Miers can be grown in high-light locations whereas Thunbergia grandiflora Roxb. can be grown in low-light locations. When using potential species in either high-light or low-light areas, attention must be paid to adjust the number of plants and pruning and grooming. Appropriate mesh size should be used when growing twiner climbers. When in doubt, 6.5 cm mesh size is suggested. During slow-growth season or in shady areas, fertilization frequency should be increased until full plant coverage is reached, after which fertilization frequency can be lowered. Overall, proper selection of suitable plants with supporting devices along with attentive management of fertilization will ensure the successful installation of indirect green façade.
Subjects
Green wall
Light intensity
Mesh size
The frequency of fertilization
Type
thesis
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