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Tuesday - September 15, 2009

From: Langhorne, PA
Region: Mid-Atlantic
Topic: Water Gardens, Compost and Mulch
Title: Poor drainage in clay soils in Langhorne PA
Answered by: Barbara Medford

QUESTION:

Our backyard has very poor drainage, to the point of up to 3 inches of rain can sit until it is evaporated. Talking to neighbors, they informed us that there use to be a terrain that ran through our yard and as people built up their yards with fencing etc the problem has gotten worse. We have attempted to fix the issue by using drainage rock and pipe but we are still having some issues. We dug about 8' down to put in a french drain also and haven't hit dirt yet either, just clay at this point. My question is are there any trees or evergreens that we can plant along our fence in this poorly draining area that will help this issue?

ANSWER:

That is unfortunately not too unusual a problem. As development of an area continues, some residents will rearrange their yard in order to redirect the natural drainage, often to the detriment of someone else. Having experienced a similar situation, we would suggest that you check to make sure there are no deed restrictions about blocking natural drainage across a property. It's possible there might be some help there, if others would take down dams or walls built to keep water from standing in their own yards.

However, since you can't bank on that, let us give you another solution, that of a rain garden. We have answered several previous questions on similar problems to yours, including one in Pennsylvania. First, we want to quote a portion of a previous answer having to do with your clay soils:

"When the weather has been dry, these expansive clay soils shrink and become permeable with small channels running through them much like the honeycomb limestone of the area.  When it rains, the water runs through them vertically until they absorb enough to expand and become impermeable.  They expand vertically as well as horizontally.  When they absorb enough water to become impermeable, the water runs off the surface.   The soil can't expand further at this point.  The water you catch in your rain garden pond is going to permeate the clay soils underneath it until they become saturated and almost impermeable."

Now, we will quote from an answer to Montgomery County PA, which is apparently adjacent to your Bucks County,  that sounds like a very similar situation:

"We have a How-To-Article Water Gardening that will give you some ideas on how to treat this area, but that is not exactly what you want. What you want is a wetland or a rain garden, with plants that can both withstand dry weather as well as having their feet in standing water for a short period. The rain garden is not only a way to deal with streams of rain water and with saturated soil, but also helps to filter out pollutants and filter the water before it goes rushing off to lakes and your water supply. Here is an article from Rain gardens of West Michigan with some basic information to get you started thinking in that direction. 

The best reference source we found was from the Wisconsin Department of Natural Resources Rain Gardens, a How-To Manual for Homeowners. It is fairly lengthy, and probably involves more than you actually need or want to do for your problem area, but it has good explanations of why a rain garden is important to water and soil conservation and quality of our water supply, while giving you an attractive, useful area in your yard.

And, finally, this website Native Rain Gardens makes our point about native plants. In the same vein, please read our How-To Article A Guide to Native Plant Gardening. Our next step is going to be selecting grasses and herbaceous blooming plants that do well in sun, tolerate wet feet, are perennial and are native not only to Pennsylvania but to the area around Montgomery County in southeast Pennsylvania. Follow the links to the webpage on each individual plant to learn more about the soil the plant prefers, expected size, color and time of bloom, etc. These are all attractive garden plants that will function well in a rain garden, but if you would like more choice, to our Native Plant Database, and do a Combination Search, selecting the characteristics and habits that you feel apply." 

Since these two areas are so close together, we are going to give you the same suggested plant list. However, we don't know exactly what your elevation is, how the land drains (away from the house, toward the house, etc), and what structures might be in the path of the drainage. From a distance, it is impossible to give you any more specific advice, but if you follow the links in the above reference in Rain Gardens in West Michigan, you will come to a section in "Getting Started" called "Choose the right place for your rain garden." As you read the various pieces of information, you will realize you are going to have to do some digging, and replacing the impermeable clay soil, in the depression you have selected to be your rain garden, with organic material such as compost, and mulch.

Herbaceous blooming plants for a rain garden in Langhorne PA

Acorus calamus (calamus)

Asclepias incarnata (swamp milkweed)

Equisetum arvense (field horsetail)

Eupatorium perfoliatum (common boneset)

Iris versicolor (harlequin blueflag)

Lobelia cardinalis (cardinalflower)

Lobelia siphilitica (great blue lobelia)

Scutellaria integrifolia (helmet flower)

Solidago rugosa (wrinkleleaf goldenrod)

Grasses and grass-like plants for a rain garden in Pottstown PA

Andropogon glomeratus (bushy bluestem)

Carex stipata (owlfruit sedge)

Schoenoplectus tabernaemontani (softstem bulrush)

 

 

 

 

 

 

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