One of the most exciting features of The Spheres are the living walls. With more than 25,000 plants woven into 4,000 square feet of mesh, these vertical gardens are an innovative demonstration of biodiversity.
Choosing the Plants
From afar, the walls offer a rich canvas of color, and up close, they boast more than 200 different species of continuous plant coverage. Like most of The Spheres’ plants, the living walls highlight flora from the world’s cloud forests, chosen for their ability to thrive in conditions that are comfortable for people.
Similar to natural cloud forests, the living walls demonstrate vertical stratification, which is the phenomena that certain plant species thrive at certain heights. In general, light at the base of forests is limited compared to the canopy. The same concept applies to humidity, temperature, and nutrient availability. In designing the wall’s plant palate, the horticulture team considered this. The base of the walls feature plants that prefer lower light levels, cooler temperatures, and more water—plants found here include many ferns, cool growing orchids, and aroids.
Highlights of the walls include a number of Phragmipedium orchids, which naturally grow on vertical surfaces in Central and South America.
Additionally, one of the walls features pitcher plants—carnivorous plants that have adapted to grow modified leaves filled with water and digestive enzymes. A few different species are represented, each exhibiting variation in trap morphology.
Beneath the Greenery
Underneath all of the foliage, is an sophisticated irrigation system that efficiently recirculates nutrients and water. Irrigation supply is pumped to the very top of the walls and slowly percolates to the bottom, fertilizing and watering plants as it moves downwards. The wall is made of a Surface Mesh that spreads nutrients to all of plants that need it. Catch basins collect excess water, as it makes its way back to a central reservoir so the process can begin again. As a result, irrigation is simple and sustainable.
Putting It All Together
How do you grow a 4,000 square foot green wall? One piece at a time. These walls are the brainchild of Horticulture Program Manager Ben Eiben. Ben and the team assembled the living walls, first by growing plants on three-foot-long panels at the greenhouse. When the panels were ready, they were transported and attached to the growing surface at The Spheres. With this careful preparation, the team assembled The Spheres’ tallest living wall, which stands at 60 feet, in only two weeks.
In addition to being a creative way to display plants, green walls also provide many benefits including reducing urban heat islands, cleaning interior airspace, and providing natural cooling and insulation for buildings. These walls are just one of many natural spaces employees and visitors can look forward to seeing inside The Spheres this year. To learn more about all of the different plants and installations coming to The Spheres, check out @SeattleSpheres on Instagram.