Rain Gardens for Dry Climates

Did you know that, in semi-arid climates like Wyoming, rain gardens play an important role in water conservation? Why not consider building one on your property?

Three Components

Rain garden design is based on three simple components:

  1. A drainage area that collects rainwater,
  2. A distribution system that connects the drainage area to the receiving area, and
  3. A receiving area that retains and infiltrates the rainwater.

When designing rain gardens in arid and semi-arid climates, particular care must be given to the selection and maintenance of vegetation. The key is to follow the principles of xeriscaping.

How to Start

You’ll want your rain garden to be at least 10 feet away from your home to prevent flooding into your house. Choose a naturally low spot in your yard, or wherever downspouts can best direct rainwater into your garden. Full or partial sun is recommended.

Whether your rain garden is large or small, the same basic principles apply.  Planning your garden on paper first will allow you to create the best appearance possible.

Choose Wisely

Use low-water-use plants. According to the EPA, native and drought-tolerant plants can drastically reduce, if not eliminate, the irrigation requirements of rain gardens. If your garden area is large enough, you can even include drought-adapted trees, as these thrive on deep, infrequent watering, and are particularly suitable.

You also should bear in mind the potential for occasional inundation. (An overflow outlet should be positioned so as to direct any overflow water away from existing buildings and structures.) Though standing water usually lasts less than 72 hours, make sure plants located at the lowest elevations can tolerate it.

Click here for a list of rain garden plants suitable for Wyoming.

Next, it’s time to lay out the shape and boundary of your rain garden, using a tape measure and string. (Be sure to contact your local underground utilities before you dig.) Then, remove the turf grass and dig about 4”to 8” deep. You can use the soil to build a berm around the garden edges, if necessary.

Healthy soil is essential to sustaining plants and treating stormwater runoff. If you suspect poor soil, it’s a good idea to amend it with 2” to 3” of organic compost.

Time to Plant

Following the design you created, place your plants in the approximate positions. As a rule of thumb, flowers and grasses should be spaced about one foot apart from each other, while shrubs and trees should be spaced according to the estimated size of the mature plant.

Once you’ve positioned the plantings, step back and take a look at the garden and the design. If you’re satisfied, start planting. Here’s how:

  1. Using a shovel or backhoe, loosen all the soil to a depth of about two and a half feet. (If you hit bedrock, consider changing the garden site, as rainwater will not drain well.)
  2. Dig an inlet or shallow trench that directs the flow of rainwater into the garden from the pavement, roof or lawn.
  3. Shape the rain garden like a basin, with the lowest point (usually 4″ to 8″ deep) at the center. This is where the water will collect and filter through the soil.
  4. Place your plantings in the soil, according to drought tolerance (put the least drought-tolerant plants at the lowest point).

Apply 2” to 3” inches of organic mulch once planting is done. This will increase water retention and pollutant removal, while also building soil structure and suppressing weeds. Composting is a good way to create a nutrient-rich mulch material for your plants.

Avoid applying mulch too close to the trunks of trees and shrubs. According to the EPA, many desert trees and shrubs react poorly when their trunks come in contact with mulch.

Once you’ve planted your rain garden, you’ll have to water it every other day for about two weeks (if it doesn’t rain), until the garden appears to be growing on its own.

About Maintenance

All landscapes require maintenance, even xeriscapes. Every rain garden requires some pruning, natural pest control, organic feeding (via mulch), weeding, and occasional watering. Your native plants are adapted to the natural soil conditions and do not need fertilizer other the nutrients in the soil and decomposing mulch. Be sure to reapply your mulch annually to maintain the recommended depth.

As your xeriscape rain garden becomes established, maintenance tasks will decrease.


Sources:

Rain Garden Network

EPA

Xeriscapes

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