RAIN GARDENS

An investment in your home, your water, your health and your future

A rain garden is a depressed area in the landscape that collects rainwater from a roof, driveway or street and allows it to soak into the ground.  These gardens are an easy and effective tool that we can use to help reduce stormwater runoff from residential properties. Planted with grasses, herbs and flowering perennials, rain gardens can be a cost-effective and a beautiful way to reduce runoff from your property, These gardens are strategically placed to intercept pollutant laden stormwater runoff until it can be fully absorbed into the ground.  Native flowering plants, herbs for cooking and medicinal purposes for you and your natural ecosystem in your area.


The water slowly infiltrates into the underlying soil. Rain gardens can come in all different shapes and sizes but are best when planted with native plants that are indigenous to your area.  These beautiful plants require little maintenance once established, have deep roots that soak up lots of water, provide food and habitat to you and the wildlife

BUILD YOUR RAIN GARDEN YOURSELF

Installing a rain garden on your property is something that most homeowners can do all by themselves while making an impact on water quality and nature. A rain garden is an investment in your home, your water, your health and your future.

Choosing a location: Choosing a rain garden location is very important and there are many things to consider. The rain garden should be located in a place that can collect as much impervious area (driveway, roof, sidewalks) runoff as possible. The best areas are generally where water naturally drains but doesn’t hold water. It should also be located at least 5’-15’ away from your home. Other things to consider are existing tree roots, groundwater table, retaining walls, utilities, overflow and setbacks/easements.  Imagine the water draining off the roof into the spouts and the water from surfaces that have collected pollutants from cars, fires planting chemicals.  As the water falls it is best to collect the flow using a dry rock river stream bed that would clean and carry the water to the rain garden. 

Sizing the rain garden: You will want to base the surface area of your rain garden on the contributing drainage area to the rain garden. You will also want to consider the infiltration rate and depth of the rain garden.

Soil Infiltration test.  This is very important if you do not know the composition of your soil.  If you have clay soil it does not drain and therefore a rain garden in a different location would be better or other rain saving techniques could be implemented, as everything helps.

Excavate the rain garden: This is where you may want to enlist in a little help. When digging to your desired depth remember that your topsoil can be amended and reused in the rain garden or spread on your property. The subsoil can be used to create the rain garden berm, amended and spread on your property, or hauled off site. Your rain garden depth will likely be between 18”-36” deep, with 6” ponding area and 12”-30” of soil amendments.

Call Dig Alert to verify no utilities are under the ground: This may be the most important step. 

Fill the rain garden with soil media mix: The soil mix placed back in the excavated rain garden, or hole at this point, should consist of ~ 50% sand, 25% topsoil, and 25% compost. Additional sand can always be added to the mix but limiting your clay content in the mix is very important. The mix should have very little clay as it impedes water from infiltrating into the rain garden and into the earth.

 

Plant and mulch: This is the fun part, choosing your plants and planting.  Remember to consider the direction the rain garden faces as the south facing slope will typically receive the most sun and heat. Consider how the plants handle water as the middle of the rain garden may be slightly wetter than the outer edges. Remember, native plants are always your best option when planting because they need little maintenance once established, will love the growing conditions, and offer benefits to wildlife all while being beautiful additions to your landscaping. 

Maintenance. Rain garden require about as much maintenance as a standard landscaped bed. In the first year weeding, watering, and raking mulch is about the extent of the maintenance for your rain garden. You may have to tweak the rain garden a bit as you see how it functions throughout the years.

 

Berms help retain water on steep slopes and can be made from excavated soil from the garden. They can be vegetated or compacted and mulched as seen above.

A rain garden is three main components: plants, soils and cover.

HOW RAIN GARDENS WORK

The existing soil within the rain garden is removed (or amended) and replaced with a more permeable soil typically consisting of a mix of sand, topsoil, and compost. These soils will allow for easier water percolation. Sizing of rain gardens is dependent upon the amount of water that is expected to enter it during a rain event. The rain garden is planted with trees, shrubs, and perennials before being covered in a layer of mulch. The completed rain garden will have a slight depression that is used to temporarily collect runoff so it can infiltrate slowly. They have the same look and feel as any other conservation landscape bed, but with the benefit of filtering the water and feeding the universe. 

Berms help retain water on steep slopes and can be made from excavated soil from the garden. They can be vegetated or compacted and mulched as seen below.

 

A rain garden is three main components: plants, soils and cover:

Plants

  • Select native plants and herbs for your zone

  • Consider sun, partial sun, shade

  • Should contribute to native wildlife

  • Should be aesthetically pleasing

Soils

  • Loose soils that offer filtration and allow easy root growth

  • Amend soils if necessary

    • 50%-60% sand

    • 20-30% topsoil (low clay content)

    • 20-30% compost 

Cover (gravel or mulch)

  • Offers soil erosion control

  • Traps moisture in soil and moderates soil temperature

  • Large stones can be used for reinforcement during storms

 

Rain gardens are made up of a bowl-like depression in the ground. On the downhill side (opposite side of where water will enter), a raised berm of soil is placed to allow water to sit in the garden are infiltrate into the soil. The shape of a rain garden is usually similar to a “kidney bean” to allow the garden to accept a wide sheet flow of runoff and consolidate it into the garden base.

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