Rain Gardens for the Reluctant Gardener

Episode Introduction

In today’s episode, Rain Gardens for the Reluctant Gardener, we chat with Steve Rodie about just how much water comes off your roof in a single rain, what the heck bioswales are, and some tried and true native plants to select for your rain garden projects.

Host Stephanie Barelman

Stephanie Barelman is the founder of the Bellevue Native Plant Society, a midwest motivational speaker surrounding the native plants dialogue, and host of the Plant Native Nebraska Podcast.

Guest Steve Rodie

Steve Rodie retired in 2020 from 26 years of teaching, research, and extension at the University of Nebraska. He is currently an Emeritus Professor of Biology and Environmental Studies at UNO. During his academic career, he focused his teaching and research on landscape plants, landscape and environmental appreciation and sustainability, sustainable landscape design, and green infrastructure stormwater management using rain gardens, bioretention gardens, and other best management practices. 

Steve is also a registered landscape architect and worked on environmental assessments and visual resources analyses for almost 10 years in Colorado and California. In 2012, he was elected as a Fellow in the American Society of Landscape Architects.

Episode Sponsors

Today's episode is sponsored by:

Midwest Natives Nursery

www.midwestnativesnursery.com/

https://www.facebook.com/midwestnatives

https://www.instagram.com/midwest_natives_nursery

Lauritzen Gardens

laurtizengardens.org

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Episode Content

TRIGGER WARNING: We occasionally discuss plants with a more eastern or western range. But we make a point to only discuss midwestern U.S. plants. Always check BONAP or other range maps to determine the best estimates of historical nativity.

625 GALLONS OF WATER

That's how much an 1000 square foot roof sheds with the average rain.

In a moderate rainstorm, imagine how much water a 2500 square foot roof sheds! Food for thought.

Why Filtering Stormwater Runoff is Important

Fertilizers (nitrogen, phosphorus,) car lot oils, heavy metals pollute rivers and streams when the polluted water just rushes straight into the storm drains.

So when we can help control the volume and the quality of the water that runs off, we can help keep our environment clean!

How Can Homeowners Find Out if They Have Rain Garden Potential?

Look around. When it rains, where is the water going and coming from? Downspouts are an obvious source of runoff, but maybe you have water rushing off of a slanted driveway, patio, or other pavement.

A rain garden would be placed close to one of these sources but at least 10 feet away from your house and not under an existing tree.

DO A DRAINAGE TEST!

Find a spot where a rain garden seems appropriate and test the soil in the center of the area.

Dig a hole a foot down and a foot wide, fill it to the top with water. Wait two hours (for it to settle) and fill it back up to the top. Stick an old ruler in the side and measure how much inches of water goes down (infiltrates) each hour.

This seems like a slog but the lowest part of your rain garden is going to be anywhere from 6-12 inches deep depending on how fast the soil can absorb the water.

If you want to skip the technical stuff start with the center of your rain garden at 3 inches deep and see if it drains in two hours.

Video on this test here: https://www.youtube.com/watch?v=rEN0NtMsvsg

You can also find the section in this file: https://extensionpubs.unl.edu/publication/ec1262/2013/pdf/view/ec1262-2013.pdf

Retained Water Helps Cool the Air

Maybe this is a basic thing but whatever, we touch on it.

Bioswales- What the Heck are They?

A swale is something that channels water, could be as basic as a ditch. But a bioswale is an area where plant species are also incorporated to further channel and disperse water.

Bioswales can be a standalone thing or attached to a rain garden. Different situations might call for one or both to be utilized.

Inlets, Outlets, and Berms, Oh My!

• An inlet is simply enough where the water comes in to the rain garden.
• Outlets are likewise "micro-pathways" where emergency water is able to flow out, especially when we get exorbitant rainfall the rain garden couldn't possibly keep up with (over an inch of rain.) Outlets should always point away from buildings and structures and in a sense go with the natural flow of the water being directed into the garden.
• Berms are mounded ground on the perimeter of the rain garden so that water goes in and in a sense, is kept in.

Ok, But, Seriously, How Deep Should A Rain Garden Be, How Big Should it Be?

A rain garden with the center depression, think the bullseye in the donut hole, at a typical 6 inches deep should drain water within 12-24 hours.

If it takes longer and you have sitting water in your rain garden, you risk damage to plants, not to mention, making ripe conditions for mosquitoes.

If you want to know the methodology of determining your depth and rain garden size, consult these publications here. Choose between the web version OR interactive PDF :

https://extensionpubs.unl.edu/publication/ec1262/rain-garden-design-site-and-selection-guide

GET YOUR SOIL TESTED!

https://midwestlabs.com/

Traditional Garden Design Touchstones

Consider:

• Plant Selection- Steve encourages short plants (under 3-4 feet) for gardens under 100 sq ft.
• Plant Placement by Height (taller in the back or middle, shorter in the front or sides, etc. etc.)
• Repetition (good for aesthetic cohesion)
• Mixing Different Plants (mixing different colors, textures, and bloom times)
• Size and Shape of Bed- Curvilinear or Rectilinear, which ideally is matched to existing landscaping
• Curb Appeal and Cues to Care- thank you, Joan Nassauer
• Multi-Seasonal Interest (again, the different bloom times)
• Habitat Value

Plants Sorted by Sun Conditions

Sun/Partial Sun 

• goldenrods- showy and stiff goldenrod are good options
• purple coneflower 
• little bluestem (higher levels)
• blue grama (higher levels)
• dense blazing star
• wild bergamot 
• Virginia mountain mint 
• common yarrow
• blue flag iris - regional native 
• 'Gateway' Joe pye weed- happy in the middle
• Helenium autumnale
• great blue Lobelia-likes it wet (disclaimer: will be short-lived)
• swamp milkweed 
• butterfly weed (rim of rain garden, highest ground)
• side oats grama (higher/upper levels)
• Bicknell’s sedge
• Sprengel’s sedge 
• brown fox sedge
• gray sedge

Shade / Partial Shade 

**Reminder: Don't put a rain garden under an existing tree, the shade should be coming from a nearby structure, but again keep the rain garden at least 10 feet from a building

• Lobelia- cardinal flower-happy in the middle (short-lived)
• Solomon’s seal
• wild ginger
• lady fern
• sweet Joe pye- happy in the middle