Render of the Narikala Ridge planting in bloom adjacent to the Sololaki neighborhood.

Because of the limited soil depths and steep cliffs, mid-century foresters used dynamite to create planting pockets on the ridge.

The Narikala Ridge area includes the historic city wall, cliffs and a tourist trail from the Betlemi Stairs. Hikers pass through the different patches as they ascend the stairs.

Drone photo showing the cascading patches of Cedar Forest, Silver Forest, Flowering Thicket and Tbilisi Chapparal.

At the Okrokana South Slope, a previous plantation of cypress and cedar is interplanted with Prunus dulcis and Cotinus coggygria nurse plants.

Okrokana South Slope planting. After removal of diseased pines, meadows species composition changed.

Workers at Kakhetis Karibche nursery prepare seedlings for the project

View of Kakhetis Karibche Nursery where seedlings are grown for the project.

© George Kolbaia

Annotated drone image of the Tbilisi Urban Forest scope and adjacent National Botanical Garden. Areas include Narikala Ridge, Mtatsminda East Face, and Okrokana South Slope.

Section of the "planting pocket" of the original Soviet era pine plantation with new, biodiverse interplantings. Diagram of "nurse planting" surrounding a sapling.

Annotated drone photo of the forest patch distribution along the Narikala Ridge. Cedar Forest, Flowering Thicket, Silver Forest, Tbilisi Chaparral.

Diagram of implementation of the forest patches, trees and shrubs and site plan

Diagrams of species mix and growth simulation diagrams

Tbilisi Urban Forest aims to improve biodiversity habitat, build resilience to climate change, and provide new recreational opportunities for citizens and tourists. In the mid-20th century, Soviet planners planted pine monocultures to reduce erosion and cool the city. The aging plantations suffered significant die-off from pests and fungi, posing a fire hazard and public safety risk. The design and research team selected two pilot areas: The Narikala Ridge is a north-facing cliffside bridging the historic city center to the National Botanical Garden of Georgia, and Okrokana, a south-facing slope in a peri-urban settlement in the hills above Tbilisi to test new approaches to afforestation.

Ruderal adapted the work of environmental scientists to create detailed spatial plans for coherent “patches” of plant communities keyed to different soil and slope conditions. The patches integrate existing trees with new saplings, shrubs, and specimen trees that are grafted into the microtopography and soil pockets carved out for the initial pine plantations of the mid-20th century. The species diversity and vertical heterogeneity of the plantings provide cover for wildlife.
The scale and complexity of the project required new tools to manage the large spatial dataset and model typical scenarios. Ruderal developed a parametric planting design tool in Grasshopper that reconciles typical planting conditions with precise site-specific spatial data. The tool allows designers to rapidly visualize the patches at different scales, adapt and optimize species mixes relative to nursery inventory, and simulate the interaction of diverse species over time. Ruderal will adapt the work from the pilot project to the remaining territory and other afforestation projects in Europe and beyond.

The saplings, shrubs, and specimen trees for the project are propagated in Georgian nurseries and collected from local seed stocks, unlike other municipal projects that rely on imported trees and shrubs. By using local species and seed stocks, the project links the city to the surrounding ecological context and supports a growing network of native plant nurseries. Drawing from this network of local nurseries, rather than importing species from abroad, significantly reduces the project’s carbon footprint.

The afforestation approach includes an additional layer of “nurse plants” to increase the new seedlings' survival rate. Each new sapling is surrounded and supported by nurse plant seedlings (mainly Cotinus coggygria) that provide shade, shelter from the wind, and protection from herbivores and improve the soil quality by adding organic matter and nutrients. Additionally, the faster-growing nurse plants provide the first visual evidence of the project’s scale and effect. After one year, the irrigation and planting project has seen nascent plant communities emerge, including planted and volunteer species suppressed by the former pine canopy.