A living median strip along the A33 for a healthier highway

Along 7.9 kilometres of the German A33 motorway near Bielefeld, 11,500 m² of Sedum blankets bring greenery back to the road. This low-maintenance solution prevents weed growth, filters exhaust gases and adds colour to the drive.

Low maintenance greenery

No mowing, watering or pruning needed throughout the year.

Filters exhaust gases naturally

Sedum absorbs air pollutants from heavy car traffic.

Supports biodiversity

Flowers attract bees and insects, even along motorways.

Greening the median of the A33

As far as the eye can see: a lush carpet of Sedum vegetation covers the median strip of the A33 motorway near Bielefeld, Germany. Over a stretch of 7.9 kilometres between Ummeln and Steinhagen, 11,500 square metres of pre-cultivated Sempergreen Sedum-mix blankets have been installed on the central reservation between the carriageways. This extensive greening effort not only enhances the visual experience for drivers but also keeps invasive species out and offers practical and ecological benefits for the long term.

Turning a median into a living landscape

The aim of this project was to turn the central reservation of a busy German autobahn into a visually appealing and ecologically functional green space—without increasing maintenance costs. Road planners were searching for a ground cover that could suppress weed growth, remain tidy year-round, and eliminate the need for mowing, pruning or irrigation. After several years of experimentation with different planting methods, the answer came in the form of Sedum vegetation blankets of Sempergreen.

Why Sedum works so well here

These low-growing succulent plants, often referred to as stonecrops, are known for their incredible resilience. Among them is Sedum acre or biting stonecrop—a native species that thrives in poor soil conditions. Unlike many other plants, Sedum stores water and nutrients in its thick leaves, not in its roots. This adaptation makes them highly drought-tolerant and ideal for environments where access is limited, such as motorway medians.

It all comes down to the layering

Holger Neisser, landscape contractor and sales representative at IGG, explains the ecological value of this solution.

Pre-cultivated and ready to roll

The vegetation blankets themselves are grown by Sempergreen in the Netherlands, where up to seven different Sedum species are cultivated together on coconut fibre mats. These mats are pre-cultivated for months on open fields, ensuring a healthy and dense plant coverage, at least 90% at the time of delivery. Once mature, they are harvested and rolled up in lengths of up to 50 metres, ready to be installed just like turf rolls.

Large-scale installation with precision

For the A33 project, a total of 11,500 square metres of Sedum blankets were laid over a 7.9 km stretch between Ummeln and Steinhagen. The installation was carried out by Internationale Geotextil GmbH, with a five-person crew working on-site for an entire month. Each 1.2 metre-wide mat was laid perpendicular to the direction of traffic and anchored between the concrete supports of the median strip using wire pins.

Engineered for performance

What makes this installation truly unique is the engineered structure underneath the vegetation. A carefully layered build-up begins with existing drainage pipes, which must remain accessible and cannot be sealed with concrete. These are first covered with sand, then 20 cm of coarse gravel. On top of this sits a geotextile fleece, followed by a mineral wool mat that acts as a lightweight, absorbent growing medium. The final layer is the Sedum blanket itself. According to Holger Neisser from IGG: “It all comes down to the layering.”

No chance for weeds, but room for biodiversity

This smart layering makes it virtually impossible for invasive species, grasses or even trees like birch, willow or elder to establish. The poor-nutrient conditions that deter other species create the perfect niche for Sedum to thrive. Even in a harsh environment like a highway median, the plants flourish and attract pollinators such as bees when in bloom.

A model for green infrastructure

This project is a perfect example of how nature-inclusive design can be applied to hard infrastructure. The A33 green median adds colour, absorbs vehicle emissions, and supports urban biodiversity. As Holger Neisser puts it, the project is “a small mosaic tile returned to nature by the motorway builders.”

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Roadside Greening

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