Adding a Wetland

 Most of us do not live on property with an existing wetland, especially if our home is in a typical subdivision. Homes built in low-lying areas are built on fill dirt arising from somewhere in the development or trucked in from somewhere else. Because of that, we often resign ourselves to landscaping with the plants adapted to our mesic or xeric conditions. Of course it doesn't have to be that way. My former home and the one I am now landscaping fit the traditional residential conditions, but there are wetland plants that I like to keep close to me. To resolve this, I have put in my first wetland.
Creating wetland conditions can take many forms and this won't be the last one I add. It's just the easiest and I have moved all of the components from my previous landscape. Eventually, I will make a more-extensive area using a pool liner and the runoff from my rain gutters/downspout. When I do, I will write about that also.
There are good reasons to create a wetland, but I'll admit that mine are pretty selfish. I just want wetland plants in my landscape because I like them. A great many wetland plants have significant wildlife value, especially for pollinating insects. The pot I installed yesterday is of that nature. The dominant plants are two species of blue button snakeroot - Eryngium aquaticum and E. integrifolium. I find these to be beautiful wildflowers and the bees find them to be an equally beautiful nectar source. It's a win-win for all of us. I could not accommodate either of these plants in my landscape if I did not keep them wet and that is impossible in my yard or that of anyone in a typical suburban setting.
This wetland has worked extremely well for me for more than 6 years and it is the easiest and least expensive approach. It does not require you to install a water source as it works on the normal rain cycle - as it would in nature. I have dug a hole in the location where I want it to reside. Here, it will receive ample sunlight. That was a problem in my former location as the trees were providing too much shade. Most wetland plants, especially those native to marshes and wet meadows, need plenty of sunlight to thrive. The hole I have dug is just large enough to fit the dimensions of the simple black-plastic pool that I purchased years ago from a popular home building supply chain. If my memory serves me right, it cost less than $20. This pool is pictured in the second photo above, but it could work as well with any-size pool of your liking.
Because this pool has no drainage, it will fill up during the wet months and dry down during the drier ones - just as natural wet prairies and marshes do. This water source, then, is purely natural and mimics the natural cycle of wet-drier within whatever region you live in. If you experience an extended drought during an inopportune time, however, it is easy to water this with a garden hose. That is something I have rarely had to do, and because very little of the water in the pool is exposed to the air above, there is far less evaporative water loss than if it was simply a pool of water.
Once you have the hole dug to the right depth and width, it is time to place the pool inside, being careful to have the soil foundation firm against the pool itself. Take the pool out after you've set it inside and make sure that the dirt below shows evidence that there were no gaps between it and the pool. If so, add a little more soil, firm it down, and level it before adding the pool once more.
With the pool firmly set in the hole, it is time to consider the planting pot. As you can see from the photo of the pool above, the pot will rest on the three "steps" and not on the bottom. This is important for two reasons (if not more...). First, you want the drainage hole(s) of the pot off the bottom so that the water in the pool can adequately wick into the soil within the pot. Second, you are not trying to fully saturate the soil as would happen if the pool filled up and the pot was level with it. By setting the pot above the pool depth, you will wick water out of the pool and the soil will stay wet/moist without being completely saturated - except during extremely wet times.
I am often asked about mosquitoes because of the pool and its lack of drainage. I have not found this to be a problem with this design as the pool rarely has standing water for long. When it does, I simply add a mosquito dunk to the open water at the edge of the pot.
 I also try to reduce the potential for breeding mosquitoes, and provide a firmer base to the pot, by adding river rock/gravel of some kind to the bottom of the pool to the level of the bottom of the pot. This reduces the depth of the open water. Here, in the photos below, you can see the granite stone I have used and the depth to which I've placed it. The pot will rest on the three "steps, but it will also have the added foundation of the crushed granite rock beneath it. As you may guess, the pot with its wet soil becomes very heavy.
The pot does not have to be deep. It is almost preferable if it isn't. It's the width that's important as this will determine how many plants you'll be able to add. Wetland plants do not have deep roots. They don't need to struggle for water as upland plants do and the deeper they go into the saturated soil, the less oxygen becomes available to them. Use a pot that is wider than it is tall - like the one in these photographs.
Once all of this is ready, it's time to add the pot. Over the years, I have simply used a commercial garden soil mix as a planting medium. Potting soil is not meant for this use as it has lots of perlite etc. for aeration. This is of no advantage to plants adapted to wetland conditions. As these plants are in pots, I fertilize them rarely; at a minimum annually.
There is no reason that you have to "live with" the growing conditions you've been given around your home. To a degree, you can change areas of your landscape to fit the needs of the plants you most want to grow. It is much easier to create a wetland than it is to make a scrub/desert, but allow your imagination to come to solutions. This type of wetland does not meet the needs of wildlife requiring open water, such as songbirds. That needs to be provided in a different way. I'll be working on that too in the months ahead. Happy gardening.