How to create a rain garden

What is a rain garden

A rain garden is a landscaped area that is specifically designed to capture and filter rainwater, helping to prevent it from running off into nearby waterways. Creating a rain garden in the UK can be a great way to improve water quality, conserve water, and add some beauty to your garden at the same time. Here is a guide on how to create a rain garden in the UK, including common mistakes to avoid and the benefits that a rain garden can bring.

How to create a rain garden

Choosing the right location

The first step in creating a rain garden is to choose the right location. The ideal location is a low-lying area that is close to a downspout or other source of rainwater. It should also be an area that is well-drained and where water can be easily directed away from the foundation of your house or other buildings.

When selecting a location for a rain garden, consider the following factors:

  • Drainage: Look for a low-lying area that can collect rainwater from roof gutters, downspouts, or other runoff sources.
  • Soil type: The soil in the rain garden area should be well-draining to ensure that water is not retained for extended periods.
  • Distance from runoff source: The rain garden should be located as close as possible to the source of the runoff to minimize the need for piping or diverting water.
  • Accessibility: The rain garden should be easy to access for maintenance and monitoring.
  • Avoid obstacles: Avoid placing the rain garden near buildings, underground utility lines, or other obstacles that may make it difficult to install and maintain.
  • Sunlight: The rain garden should receive at least 6 hours of sunlight per day to support the growth of native plants.
  • Size: The size of the rain garden should be proportional to the amount of runoff it will receive.
  • View: Consider the visibility of the rain garden from your home or other nearby structures, as well as the view it provides from your property

Designing the garden

Once you have chosen the right location, it is time to design the garden. The design should include a combination of shallow-rooted plants, such as grasses and wildflowers, and deeper-rooted plants, such as shrubs and trees. This will help to ensure that the garden can filter and absorb a wide range of pollutants from the rainwater.

When designing a rain garden, consider the following steps:

  • Determine runoff volume: Calculate the volume of water that will drain into the rain garden from your roof, driveway, or other hard surfaces.
  • Determine size: Based on the runoff volume, determine the size of the rain garden required to manage the runoff.
  • Shape: The rain garden should have a shallow depression in the center, with a slight slope towards the outer edges to allow water to drain away.
  • Choose plants: Select plants that are native to your area and can tolerate the range of soil moisture levels that occur in a rain garden.
  • Soil amendment: The soil in the rain garden should be amended with organic matter to improve its ability to absorb and retain water.
  • Edge treatment: The edges of the rain garden can be defined with rocks, bricks, or other materials to create a clean, finished look.
  • Maintenance: Plan for routine maintenance to remove debris, maintain plant health, and ensure the rain garden continues to function properly.

Installing the drainage system

To ensure that the garden can filter and absorb pollutants effectively, it is important to install a drainage system. This can be done by digging a shallow trench around the perimeter of the garden and filling it with gravel or other drainage materials.

To add drainage to a water garden, consider the following steps:

  • Prepare the site: Excavate the area for the water garden and level the site to create a shallow depression.
  • Select materials: Choose materials such as gravel, rocks, or perforated pipe to create a drainage layer in the bottom of the water garden.
  • Add drainage layer: Place the drainage material in the bottom of the water garden and compact it to ensure that it is level and stable.
  • Install plants: Choose plants that are native to your area and can tolerate a range of soil moisture levels.
  • Add soil: Fill the water garden with soil to a depth of at least 6 inches, being careful not to damage the drainage layer.
  • Mulch: Apply a layer of mulch to the surface of the water garden to reduce evaporation, control weeds, and conserve soil moisture.

Planting the garden

Once the drainage system is in place, it is time to start adding the plants. When choosing plants, it is important to select those that are well-suited to the local climate and that can tolerate occasional flooding.

When choosing plants for a water garden in the UK, consider the following:

  • Marginal Plants: These plants are suitable for planting in shallow water along the edge of the water garden. Examples include iris, water forget-me-not, and marsh marigold.
  • Oxygenating Plants: These plants release oxygen into the water and help to reduce algae growth. Examples include Canadian waterweed, hornwort, and water milfoil.
  • Floating Plants: These plants float on the surface of the water and provide shade and cover for fish and other aquatic life. Examples include water lilies and water hyacinth.
  • Bog Plants: These plants are suitable for planting in wet soil near the edge of the water garden. Examples include horsetail, sedges, and marsh marigold.

When planting in your water garden, consider these steps:

  • Choose plants: Based on the type of water garden and the amount of light it receives, select plants that are well-suited to your conditions.
  • Purchase plants: Purchase healthy, well-established plants from a reputable nursery.
  • Plant in pots: For larger plants, plant them in pots filled with aquatic soil and sink the pots into the water garden.
  • Submerge plants: For marginal and oxygenating plants, plant them in soil at the appropriate depth and partially submerge them in the water.
  • Float plants: For floating plants, simply place them on the surface of the water and allow them to float.
  • Provide support: For tall plants, such as water lilies, provide a stake or cage to support the plant as it grows.

Maintaining the garden

Once the rain garden is established, it is important to maintain it properly. This includes regular watering, fertilizing, and weeding. It is also important to check the drainage system regularly to ensure it is functioning properly.

Avoiding common mistakes

A common mistake that people make when creating a rain garden is choosing the wrong plants. Some plants, such as those with deep roots, may not be well-suited to a rain garden and may actually cause more harm than good. Another mistake for those looking how to create a rain garden is not ensuring the garden has a proper drainage system, the garden should be dug into a depression, and the soil should be amended to ensure water can drain away quickly.

Benefits & summary

Water gardens add beauty to your garden and benefit the environment. They do this by delaying the impact of rain on local river levels and requiring less water to maintain in times of drought. This helps to preserve these water bodies for other uses whilst adding a beautiful and naturally regulating addition to your garden.

13th February 2023
Tom McNamara


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