Rain gardens are a fairly new concept for people to think about with our recent severe drought, making many more people realize pure clean water is our most precious resource. Whether we are in a drought or flood, we all benefit by capturing rain through rainwater harvesting and holding it on our property. With the drought we wanted to keep our rain water in our rain barrels to ourselves to use for watering our landscapes. With the recent severe flooding, rain gardens can help ease the force of flooding and erosion by allowing storm water to infiltrate slowly into the ground. Less storm water runoff means less severe flooding and less pollution and sediment entering our rivers and lakes while also recharging our ground water supplies.
The shift to more environmentally sound landscaping means more people are looking for ways to give back to the earth for the benefit of everyone. My own inspiration for adapting rain gardens into my landscaping practice comes from my deep belief that gardens can be more than beautiful; they can be useful for people and animals by providing much needed wildlife habitat and rainwater for gardens.
Simply put, rainwater harvesting by way of rain gardens are concave depressions covered with plants that store water for direct landscape use. It is a radically different concept from the current landscaping trend of getting rain water off our property as fast as possible by putting it into concrete and metal channels.
Building Your Rain Garden (General rules, research rain gardens and rainwater collection before digging)
Size:
* An easy general rule for the area of the rain garden is equal to 1/3rd the size of area that rain water will run off from and into the rain garden.
* Consider roof, lawn, and patio areas to determine the size of the rain garden area size, if rain water runs off these areas and is directed to the rain garden, it needs to be included.
* Add all these areas together and divide by 1/3rd; that is how many square feet your rain garden area should be when completed.
* Several rain gardens can be connected together to handle large rain events.
* Such holding areas can be chained together through spillways. You can create holding areas by digging out depressions and keeping the resulting soil as a berm or by using berms, moats, or soil terracing to make flat areas hold water.
Depth:
* Make a depression 12 to 18 inches deep throughout the area of the rain garden.
* Make the bottom level and flat, being careful not to compress the bottom soil making it hard as rock.
* Slope will determine how deep to make your rain garden, the more slope you have, the deeper your rain garden will need to be.
Soils:
* The soil in your rain garden should be a mix that will allow fast infiltration of water and good root growth, such as a mixture of 40% expanded shale, 30% compost and 30% topsoil.
* Allow for a 3-inch layer of shredded hardwood mulch.
* A useful example of layering from top to bottom:
3” of mulch
6” mix of native soil, expanded shale and compost mixed thoroughly together
3” of stone aggregate such as gravel
* Type of soil and slope determine how deep and how large the rain garden should be.
* A bottom drain may be needed in highly compacted clay soil situations if too much rain will constantly overwhelm the rain garden.
* You should, however, be aware that digging may expose poorer quality subsoils unsuitable for landscape plants.
Plants:
* Native species
* Berry and nectar producers
* Combine shrubs, wild flowers and grasses
* The types and numbers of plants in your landscape, along with their growth stages and sizes, determine the amount of water your plants need to be healthy.
* Because rainfall varies throughout Texas, different plants have become adapted to conditions in different regions of the state.
* Deep-rooted plants native to your region are the best choices for your landscape because their water requirements are usually met by normal rainfall amounts.
* Plant combinations for our soil and climate (some non-natives are okay).
Spring blooming:
· Yarrow with bergamot (full sun)
· Blue False Indigo with yellow columbine (shade)
Summer blooming:
· Boneset (Eupatorium colestinum) with purple perilla (an herb)
· Mexican Milkweed with daylilies (deep rooted sun plants)
Fall blooming:
· Goldenrod with purple asters
· Blazing Star with Blue Mistflower
Winter interest:
· Native grasses will have attractive seed heads, left untrimmed until late winter so the birds will have a food source
Benefits of Sustainable Landscaping and reducing the size of your lawn:
* Attract Wildlife
* Hardier lawns and gardens (native plants are drought resistant)
* Save water and money on water bills (the average lawn consumes 10,000 gallons of water annually)
* Enhance passive recreational opportunities (bird watching, garden photography)
* Reduce pollution from chemical pesticides and fertilizers
* Reduce air and noise pollution from lawn equipment