Q: Our backyard has very low spots where the water ends up after heavy rains. How do I deal with this? I would like to plant a garden of shrubs and perennials but don’t think many can take that much water. Red maples and birch seem happy, but the hydrangeas I planted last year all died. It gets quite a bit of sun.
Answer: Most plants will not tolerate sitting in standing water or saturated, soggy soil for long periods. You may be able to add one to two inches of soil to fill in low spots or raise the grade enough so that water will run off better or at least not accumulate there. A steep grade is not necessary or desirable because in dry years you do want the water to sink into the soil and down to plant roots.
You may have a good location for a rain garden. Many plants love this environment — some stunning natives in particular, such as button bush and clethra. (Both are also butterfly magnets!) Take a look at the University of Maryland Extension webpage on stormwater practices.
Don’t get bogged down (no pun intended!) with details. Just plant what likes “wet feet.” Native plants are the best. For more plant choices, look at the U.S. Fish & Wildlife Service’s excellent publication, “Native Plants for Wildlife Habitat and Conservation Landscaping: Chesapeake Bay Watershed.” In the lists, ‘Plants for Freshwater Wetlands and Other Wet Sites’ should be helpful. (There is also the equivalent online database, http://www.nativeplantcenter.net/.).
You may not have standing water continuously in the future. However, it is predicted that we can expect a lot more wet years and extreme weather ahead because of climate change. A rain garden is a smart way to handle this, as long as this spot does not hold water all summer (and breed mosquitoes). When you install a rain garden, the plant roots will be pulling in the water and drying up the low area, too.
By Ellen Nibali, Horticulturist, University of Maryland Extension Home and Garden Information Center. Ellen writes the Garden Q&A for The Baltimore Sun.
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Before you add soil to change drainage, make sure it stays on your property and does not become your neighbor’s problem. And check local ordinances on rules for grading.
Thank you for commenting. Yes, it is a good idea to check with your county’s environmental department or Soil Conservation District to ask about regulations on grading/sediment management. https://mde.maryland.gov/programs/Water/StormwaterManagementProgram/Pages/erosionsedimentcontrol.aspx
Raising the grade does not really get rid of the problem, it just covers it up with a surface that can be planted on. The soil may be saturated right below the surface. It is therefore important to select plants that can live in that shallow portion between the surface and the saturated layer just below.
I love the tree frogs that come from the standing water, but not the mosquitos.
Yes, mosquitoes can complete a life cycle in just four days where there are sources of standing water. Mosquito dunks containing Bacillus thuringiensis israelensis (Bti) can be used in standing water to kill the larvae.
Thanks. I need to check into that. Hope it doesn’t kill everything in the water. In love our dragon flies
While adding soil over grass and weeds is easy, one must be cautious around existing woody plants to respect their root crowns. Don’t kill one tree/plant when plant another.
Correct. No more than 2 to 4 inches of soil should be added on top of existing tree roots. Adding a layer of soil that is too thick a can starve the root zone of oxygen.
Is your backyard a “designated wetland ?” If if is, you can do nothing.
For those who have questions about Maryland regulations on activities in or around tidal and non-tidal wetlands and waterways, this page of FAQs is a good place to start. https://mde.maryland.gov/programs/Water/WetlandsandWaterways/Pages/faqs.aspx
Trees (that like wet feet) can suck up a lot of water.
That’s correct. In addition to the trees mentioned in the article, black gum (Nyssa sylvatica), American sycamore (Platanus occidentalis), black willow (Salix nigra), and hackberry (Celtis occidentalis) are some native trees that tolerate wet areas and occasional flooding.
We have different versions of the same trees here (except for the species of Nyssa), but because they are dormant through winter, they do not consume any moisture when the soil is most saturated. Of course, the plants that are in the saturated area here are also dormant through winter, so do not mind the extra saturation.