Stormwater Planters

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A building displaces all the water that used to fall on the ground at its location. With nowhere to go, rainwater hitting the roof gets funnelled together and a concentrated stream rushes down the drainpipes. You can help reduce flash flooding and have that water work for you with a stormwater planter.

A stormwater planter is a planter that is watered by and helps slow down the flow of stormwater, which is what we call precipitation once it lands (on a building, pavement, other structure, or the ground). Drainpipes are redirected into the planter, where the water spreads across the surface of the soil and then slowly soaks in. Some models are completely filled with substrate, others have tanks at the bottom that hold extra water. Plants are watered by the drainpipe, while the plant roots and the substrate help to filter and slow the water. Extra water collects in the tank and is slowly released over time. This helps keep excess water out of the drains during a storm, with all the benefits of plants on top. Stormwater planters are excellent options for small spaces and can be home-made.

What are we learning? How are we adapting?

The best plant choices and designs for stormwater planters are still being studied. We are trialling two methods on one building at RBGE.

Pathway planters:

These planters are designed by the company SUDSPlanter, and are part of the Climate Ready Craigleith initiative in partnership with Scottish Water. Sensors within the planters take soil moisture readings at four different depths, and that data is being studied by PhD student Isla Kendall to understand how different plant communities in the stormwater planters influence the flow of water. The two silver boxes intercepting the drainpipe above and below the planters are inflow and outflow meters, precisely monitoring how the planters change the flow of water. After a storm event, water is captured within the planter and nothing exits for a period of several hours, lessening the inflow on our rivers and helping to prevent combined sewer overflows. How might the impact of water surges change if there were stormwater planters on drainpipes all throughout the city?

As part of Climate Ready Craigleith with Scottish Water, residents of the Craigleith neighborhood of Edinburgh received planters customized with one of three plant mixes: aesthetic, wildlife friendly, or utility. Planters can be used by residents and businesses for a variety of purposes, but all contribute to responsible water use within the city. Scottish Water and RBGE’s research into these planters is ongoing.

The sides of these planters are timberclad using larch wood felled at our Benmore location due to phytophthora vulnerability. Climate change does not just affect how and when we get storms – climate change also affects the movement of pests and diseases. Our environment remains deeply connected in many ways.

East Gate planter:

The crossover of nature (“green”) and the built environment (“grey”) can be the messy middle. The East Gate cottage is a listed building, with cast iron drainpipes. While retrofitting cast iron pipes is entirely possible, it can be a longer process. Instead, we are employing a different method of water management to cascade into the beautiful stormwater planters: a rain chain. Rain chains are simple devices that redirect water flow off a roof in much the same way as a spoon placed into a water pitcher. The water flows off the roof, down the chain, and into the plants. Our chain is made of stainless steel. Watch the water dance down the links, and listen for the gentle soothing sound.

Back planters:

Which stormwater planter design is best? ‘Best’ can mean many different things with a feature that accomplishes so much: stormwater detention, beautification, pollinator resources, biodiversity. The two back planters, originally featured at COP26, are a water-suspension system planted with a native species plant mix, installed in early 2024. Stormwater passes through the drainpipe and directly into a stony soil, watering the plants and being filtered by their roots and substrate. In this system, the substrate runs all the way to the bottom and excess water fills the spaces in between the soil grains.

These planters include one of our ten Scottish Plant Recovery project species: the nationally rare and endangered alpine blue-sow-thistle, which prefers this consistently wet but free-draining soil.

Plant species:
- Luzula sylvatica (wood rush)
- Rumex acetosa (broad-leaved sorrel/garden sorrel)
- Salix lanata (woolly willow)
- Cicerbita alpina (alpine blue-sow-thistle)
- Deschampsia cespitosa (tufted hairgrass)
- Trollius europaeus (globeflower)
- Ligusticum scoticum (Scots loveage)
Publications and Further Information:

Craigleith Flooding Project Sees Residents Helping to Capture Rainwater - Scottish Water

Royal Botanic collaboration delivers sustainable drainage insights | SuDSPlanter®