The Rain Garden

The climate is changing and rainfall is becoming more frequent and intense. Our Raingarden is an experimental garden adapted to meet the challenge of heavy rainfall events and to monitor their impact.

The Changing Climate

In Scotland, heavy rainfall is becoming more frequent and intense.

 

Rainfall in the Garden 1977-2017

This graph shows the upward trend in rainfall over the last 40 years.  With climate change likely to alter rainfall patterns and bring more heavy downpours, we expect flood risk to increase in the future.

Our Raingarden

The Botanics' Raingarden measures 20 metres long by seven metres wide and is located at the southside of the Garden.  It is a shallow planted basin that naturally allows rainwater to drain into the ground. 

The Garden's existing soil has been mixed with compost made on site as well as sand and fine gravel to a specified particle range size. The composition has been specifically developed for use in the Raingarden to allow for water infiltration but also to provide organic material and nutrients to support the plants.

The Raingarden features a selection of Scottish native plants and non-native plants many of which are known to soak up water and thrive in boggy areas. Plantings include primulas and hostas as well as the rare Alpine Sow Thistle Cicerbita alpina which can only be found on four sites in Scotland and is part of a conservation programme at RBGE.

The location, known previously as the Birch Lawn, had suffered historically from waterlogged lawns, submerged tree and shrub roots and flooded paths.  Teams from RBGE and Heriot-Watt University will be using the Raingarden as a living laboratory, investigating the plants best placed to help the Raingarden thrive and monitoring how it performs during different rainfall events.

 

 

Plants and Biodiversity

The Raingarden features a selection of Scottish native and non-native plants.

The selected Scottish native plants include: Succisa pratensis, Anthyllis vulneraria, Filipendula ulmaria, Knautia arvensis, Cicerbita alpina and Festuca altissima.

The selected non-native plants include: Aruncus gombalanus (China), Gunnera manicata (Brazil), Ligularia fischeri (E Asia), Aquilegia Formosa (Western N America), Primula poissonii (China), Rodgersia pinnata (China) and Hosta sieboldiana (Japan).

A number of established native and non-native trees were already growing at the Birch Lawn, including: Alnus glutinosa (native), Betula pendula (native), Corylus avelana (native), Quercus robur 'filicifolia' (cultivar of a native species), Alnus japonica (Japan), Alnus rubra (N America), Betula alleghaniensis (NE North America), Betula papyrifera (N North America), Betula nigra (USA), Corylussie boldiana (Japan, Korea), and Populus alba (S and central Europe).

As well as capturing water runoff, this shrub and perennial mix is perfect for encouraging and attracting a great diversity of wildlife to the area. The diversity of flowers will provide nectar sources for insects and bees. Leaving stems of the perennials and grasses standing over winter will provide a home for many invertebrates, as well as food for seed eating birds.

 

Raingarden Design Features

Raingarden design features

 

Edinburgh Adapts

This project was developed by the Heriot-Watt University and RBGE as part of the Edinburgh Adapts - driving adaptation actions for the capital project, which aims to help the city adapt to the challenges of a changing climate.

 

Further Reading

The Raingarden was created in partnership with