Rose Garden, Mirabell Gardens, Salzburg
Renovation of the historic rose garden with RETENTIS® successfully completed
The rose garden in Salzburg’s Mirabell Gardens has been completely renovated, and we at AgroBiogel were delighted to be part of this special project with our product RETENTIS®. As part of the renewal, around 2,400 new rose bushes and the new box hedge edgings were treated with RETENTIS®. For every rose, 100 grams of RETENTIS® were worked into the root zone to support a stable supply of water and nutrients in the first years.
After around three decades of use, the rose garden showed clear signs of wear. The soils were considered depleted, many rose bushes were over-aged and the soil was heavily overgrown with weeds. The existing plants were therefore cleared and the soil in the beds was removed completely. A special rose substrate was then brought in to form the new basis for the planting.
The redesign with new rose varieties, some of them insect-friendly, fresh box hedge edgings, decorative gravel and various ornamental perennials was carried out successfully. This has created the conditions for the rose garden to shine in full bloom again and delight visitors for many years to come.
The officials of the City of Salzburg emphasised the importance of this investment. The secured funding made it possible to restore this gem in the Mirabell Gardens to new splendour while creating a successful example of cooperation between the municipal gardens department and the construction department.
Modern irrigation and RETENTIS® for the best start
Hot summers in particular show how important green spaces are in urban areas. With new plants, a modern irrigation system and a well-thought-out soil concept, the rose garden has been made fit for the future. The redesigned area is an easily accessible place that both visitors to the city and the people of Salzburg should enjoy for a long time.
One technical focus of the renovation was the installation of an artificial irrigation system. The irrigation pipes were laid at a depth of around 30 centimetres. This position protects the pipes and at the same time encourages the roses to root deeply. Water is not only available right at the surface, but where the roots are meant to develop in the long term.
This is exactly where RETENTIS® from AgroBiogel comes in. The product was worked into the root zone of the around 2,400 roses and the new box hedge edgings. 100 grams of RETENTIS® were mixed in for every single rose. In total, around 240 kilograms of RETENTIS® were used for the roses alone. RETENTIS® stores water and nutrients in the soil and makes them available in the root zone. This supports the supply during the first, particularly sensitive years, while encouraging the plants to form deeper roots.
In this way, the critical initial phase after planting is supported. Combined with the fresh rose substrate and the new irrigation, very good conditions have been created for the plants to develop.
Historic structure and modern accessibility
Despite the extensive technical and horticultural renewal, the historic character of the rose garden has been preserved. The structure along Mirabell Palace was largely retained in line with the requirements of monument protection. Paths and beds kept their arrangement and position, so that the characteristic impression of the garden is maintained.
AgroBiogel and RETENTIS® as partners in this flagship project
We at AgroBiogel are proud to have contributed to this important project in the heart of Salzburg with RETENTIS®. The combination of a listed historic garden, climate-resilient planting, modern irrigation and innovative water storage technology shows how historic green spaces can be taken sustainably into the future.
We are particularly pleased that grünplan Landschaftsarchitekten deliberately integrated RETENTIS® into the planning and that we were able to attend the site meeting with all parties involved on Monday, 17 November 2025. The work was carried out by Jakel Grünbau in close cooperation with the dedicated team of the Stadtgärten Salzburg.
The rose garden in full development
A few months after replanting, the rose garden in the Mirabell Gardens is already showing its summer side. The roses have become established, the beds are densely planted and the historic garden once again presents itself as a colourful attraction in the middle of Salzburg.
The development over the first summer is particularly exciting for us. RETENTIS® was placed directly in the root zone at planting and remains effective there for the long term. There, it helps keep water in the soil available to plants for longer and improves conditions in the immediate root zone.
The current pictures from summer 2026 show how the newly planted rose beds have developed since the renovation.
Impressions from the rose garden in summer 2026
RETENTIS® supports the new roses and box hedge edgings in the rose garden of the Mirabell Gardens in the root zone over the long term. The project shows how soil water storage can be used as part of modern, climate-adapted green space planning.
If you are interested in using RETENTIS® in your own garden, landscaping or municipal greening projects, feel free to get in touch with us.
