What do you do with swamp-loving plants when you don’t have a swamp? Well, you can water them endlessly, give up and dispatch them to the compost heap or make a new home for them in a raised-bed swamp.

Thriving swamp

In spring, our “swamp” plants showed us how much they appreciated their wet home by putting forth new growth.

Photo Credit: © Pennystone Gardens

Clothesline for radius

To help draw a nice sweeping curve with a large radius, tie a length of scrap clothesline to a pair of good-sized tent stakes. One goes in the ground, and the point of the other will draw a perfect line at whatever distance the line is – or you can tap the outside stake into the ground to mark a fixed position.

Photo Credit: © Pennystone Gardens

Pond tarp for swamp

With the soil dug out and a couple of inches of sand tamped into a shallow bowl, the pond tarp is laid out across the new bed.

Photo Credit: © Pennystone Gardens

Four inch pipe

One of my essential tools is a 4-inch sewer pipe, 84 inches long (the standard width of my garden paths). The pipe is useful for quick measuring, as well as for leveling side-to-side, smoothing and keeping grades up and down on a gentle line.

Photo Credit: © Pennystone Gardens

Finished swamp bed

Our new raised-bed swamp was done in one weekend and cost about $75, most of which was for the tarp.

Photo Credit: © Pennystone Gardens

Rhododendron arborescens

Among the benefactors of a nice wet spot is a Rhododendron arborescens, which bloomed gloriously for the first time under its new swampy conditions.

Photo Credit: © Pennystone Gardens

Believe it or not, this is a relatively easy weekend makeover – and in our case, the project had added advantage of fixing other design problems at the same time. Our raised-bed swamp began with the mistake of trying to grow an assortment of plants that really like wet soil – in soil that wasn’t really wet. You’re probably familiar with the problem. Every gardener, at one time or another, tries to cheat habitat with excess optimism about light or moisture, only to wind up with plants that languish in places they really don’t belong.

We had some azaleas, hibiscus and swamp milkweed (among other plants), and they predictably weren’t doing well. Mostly they were struggling to stay alive, especially when one of Pennsylvania’s regular dry spells arrived to bake everything to a crisp. Of course I’d water constantly, but that’s not the best conservation practice – especially when you have a well that you need water from, too.

One day I was reading about a species that “requires good drainage,” and I got the bright idea of creating a bed with absolutely awful drainage, like you’d find in a swamp, to help me deal with our struggling plants. Conveniently, there just happened to be an old raised bed that had a few annoying issues: The stone wall around two sides had a sharp corner, the adjacent path was uneven in width, requiring extra passes with a mower, and the bed was overrun with groundcover plants (mostly foamflower and a spicebush) that could be put to better use elsewhere.

A secondary problem was a little service path that meandered through a large island bed and made a sharp turn and dropped from a big stepping stone to the lawn. That step was a nifty idea at the time, but it was a nightmare when using a wheelbarrow. So a second part of the attack was to straighten the service path.

Now on a roll with scribbled plans at the kitchen table, I also planned to repair the soil and wall on another side of the island bed, converting that into a “dry” bed for species that like to cook in the sun. I wanted to put a gentle curve on that wall, too.

Most exasperating was the bed’s sharp corner, which would snag the tires of the cart being pulled by a garden tractor almost every time I made the corner. Even worse was the long length of a leaf shredder in tow. I’ve learned that a nice smooth curve is much better, and one afternoon I spent some time in an open area discovering that a 10-foot radius is a practical minimum curve when pulling a large trailer.

So I made a giant compass from two tent stakes and a scrap of clothesline. I picked a center point in the new service path route behind the emptied raised bed. Now the garden became rounded – and bigger! Next, I checked the path between the two raised beds for width. (I like my lawn paths to be 84 inches, the width of two passes with mower deck, as well as wide enough to negotiate tractors and trailers through the garden.)

After moving dozens of plants and a large shrub to better locations, I disassembled most of the stone wall and stored it off to the side. I laid the base stone for the new outline and began replacing the wall. When I got to a wall height of about 8 inches, I paused to get into the bed and dig out even more earth, now going below grade to create a big shallow bowl about 15 feet in diameter. I brought in a few inches of coarse sand into the bowl and tamped it firmly into place for a nice smooth base.

Next came an ordinary pond tarp I bought from a local home-supply store. The plan was simple: If the tarp prevented water from running out of the bowl, a certain amount of moisture would always be present for all my swamp-loving plants in the soil above. If it got too much water, the excess would just overflow out of the stone wall.

With the tarp in place, all the original soil – plus some sand – went back into the bed. I built up the stone wall as I went. As it got to about 18 inches above grade, I used additional sand and stone to create the new service path in a nice gentle grade down to the lawn. Silty humus and lots of shredded leaves topped it off, and I moved the first of the plants into their new home during late autumn. (I was making some first class muck!)

But this weekend project paid off nicely: I successfully created a new habitat that was really wet no matter how long it had been since rain fell. All the plants are growing beautifully – and even blooming dramatically for the first time since I bought them.

I’ve never actually watered this swamp bed bed, and I don’t need to. It grabs the slightest amount of rain and holds it in that “cistern” that’s 24 inches underneath – sort of a rain garden in reverse. And now I can drive a tractor around that corner and smile. Even better: The only cost was the pond liner, a little bit of sand and a weekend of work! (Hey, sometimes “feeling swamped” isn’t a bad thing…)