Placement of Rain Garden

Question: Hello.

I am planning to install a rain garden in my backyard and could use some help with the placement. I have attached a photo that shows the space I'm considering. It's next to an American holly tree at a site where water often pools on rainy days. Rainfall flows down a hill on one side and the water from my basement's sump pump empties there on another. I think this would be a decent spot but I'm concerned about the holly tree. Could placing a rain garden here affect the tree? Could this cause the tree to lean over time?

I'm also wondering if you have any resources you could share about installing a rain garden. I could use all the help. :)

Thank you!

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied March 02, 2023, 12:47 PM EST
response: HI,  American holly does sometimes grow in damp soils and near open water in the wild, but a tree not accustomed to more water than it has been getting so far might become stressed, even if temporary. If it has been accustomed to this amount of water from the sump pump and drainage, it is probably ok with it there if its not adding more to the root zone.Rain gardens are constructed elements of the landscape. Their intended function is to collect runoff, and filter it before it leaves the property, which means usually the garden is dug-out and filled in a specific way so that water can collect yet drain slowly; this means that digging into the holly's root zone may cause more damage than just natural flooding since it could kill some roots. It appears in the photo that the drip line of the Holly is to the area where you would like the rain garden, meaning that there are probably and abundance of roots there where you would be digging. Instead of a constructed rain garden, maybe planting species known to tolerate soil sogginess in that area would be sufficient.  There are a number of native plants that can tolerate 'wet feet' while the water pools in that area before draining. The Alliance for the Chesapeake Bay has a comprehensive publication with an extensive list of plants that do well in these environments. We do have some helpful links if you would like to explore the possibilities of installing a rain garden.  There is also a link for a nicely illustrated publication that could be helpful, Rain Gardens Across Maryland. It explains taking the measurements of impermeable surfaces and other runoff to determine the retention capacity of the rain garden. You can also try to search for a professional to help on the Chesapeake Bay Landscape Professional page. It has an option to filter for rain garden specialists. Montgomery County (even though this isn't your county) has the RainScapes program that could give you some more information even though the rebates wouldn't apply. Chesapeake Bay Trust website also lists different programs in various cities/counties as well as resources and information on Rain Gardens. Baltimore City is listed.  You could also look into the Bay Wise Program and contact your local Master Gardeners office to inquire about that.  This is a lot of information to get you pointed in the right direction with either plants that would work for you in that area or exploring more about rain gardens. If you have further questions with it, feel free to continue to reach out.  Emily

responder: The Question Asker Replied March 03, 2023, 4:04 PM EST
response: Hi, Emily.   Thank you for providing so much information! I'll refer to your reply for years to come.    Josh

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied March 03, 2023, 4:15 PM EST
response: You're welcome!