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The idea of Growing an Edible Rain Garden might have been a foreign concept a decade or so ago but now nearly every new home in Portland seems to be giving some thought as to what to do with all that excess rainwater that comes rushing out our downspouts during the wet winter season. And for good reason! The more property owners can mitigate and take responsibility for the water falling on their property and harvest that abundance of moisture by storing it in plants and soil the less goes into our waterways carrying all the lovely urban pollutants along with it.
The City of Portland has come out with an excellent piece of literature on how to build a rain garden for any urban situation… https://www.portlandoregon.gov/bes/article/474026
Whether you have a tiny piece of neglected dirt that the downspout erodes each year or a large lawn you’d like to convert to a more ecological garden, there’s certainly a way of capturing and utilizing the water that collects from our roofs in a more useful way than we’ve done in the past.
And while the need for more rain gardens around the city is certainly apparent after our last downpour, we’ve noticed a pattern across many rain gardens around the city…they’re kind of boring. They’re certainly functional and doing a great job of filtering pollutants, transpiring soil moisture back into the atmosphere and they’re great at storing the excess water in plant tissues but it seems as though all we ever plant in them are the same juncuses and sedges on every block. It makes sense as they’re easy plants to come by, usually pretty cost effective to procure and install, and they can tolerate our summer dry season as well as our winter rain. But we started wondering a few years ago what else could we plant in our rain gardens, specifically what kind of interesting edible species could we utilize for this unique niche in the urban environment…
The first obvious candidate was the mighty Aronia berry! Aronia grows in near wetland conditions in the wild and has no problem in even the wettest, lowest parts of rain gardens we’ve tested them in. While they do need some supplemental watering in summer, at least to get established, they make a great rain garden candidate for their love of wet soils.
So then we got to thinking, well if the aronia berry works, then surely Dwarf Shipova will work as it is grafted onto aronia rootstock! And if we have a dwarf shipova that means we can also graft a European Pear onto that Shipova, utilizing the shipova as an interstem or simply creating a multi-graft, multi-species tree and suddenly we are growing pears in the soggiest of soils! Hurray for the mighty wet footed aronia!
Then on a walk through Laurelhurst Park one day we saw one of our favorite plants, Chilean Gunnera, growing right on the pond’s edge, and thought to ourselves, well shoot dang, Chile has a wet winter, dry summer climate, I bet Chilean Gunnera would thrive in our rain gardens! Perhaps to the point of taking them over! And it certainly has. Placed between similarly vigorous Juncus plants to keep the Gunnera in check this young gunnera plant adds excellent texture to this small confines rain garden at the edge of a downspout. A few pitcher plants right at the edge of the downspout fatally capture curious ants while also keeping the neighborhood kid’s botanical curiosity piqued.
Another obvious choice as we were pondering what plants from around the nursery might work at the end of our driveway where irrigation water pools up in the summertime was the willows! The Salix genus is a diverse one so the options were many, but what better option could there be in such a lovely genus than the basket willows! Sequester your runoff water and weave with it too!
Of course the juncuses always make an appearance as they’re absolutely foolproof and given their evergreen foliage they continue to transpire and pull moisture from the soil year round, a very important consideration when planting a rain garden. But the added textures of willow, aronia, gunnera, and other wet soil loving species such as hardy gingers, Highbush Cranberry, and the many options for grafting onto aronia make a much more useful and interesting rain garden. Around the drier edges of the garden also has many possibilities as almost anything that is slightly tolerant of wet soils can be planted there and will benefit from the added moisture nearby, placing roots as near or far from the super saturated areas as is useful for the plant. The guide in the link above shows many different patterns, species ideas and planting schemes for different rain garden scenarios, though they use almost exclusively Northwest native plants, but let’s consider throwing a few new species in the mix. Look at wetlands in the wild and the assemblage of plants found growing in them and find analogous species that serve your purposes better.
Where there is water there is life, making the rain garden one of the most fun areas in the landscape to play with and see how water moves through our landscape and how plants react to it. We’ve seen incredible results just from planting the appropriate species at the edge of a downspout. Areas that were previously unsightly nuisance puddles have disappeared, sometimes in as little as a year due to root penetration, the additional organic matter, and the transpiration that occurs all winter from those plants. Think of your rain garden plants, especially those with evergreen foliage, as nature’s SUP pumps. They’re constantly taking moisture from the soil, which could be leaking into your basement, and turning it into plant tissues and transpiring it back into the atmosphere or penetrating deeper into the soil to allow it to percolate and become groundwater. Experiment with different species in whatever climate you live in and see what new species you might add to the list of rain garden plants!
And if playing with water and how it moves through our landscape interests you check out the rainwater harvesting guru Brad Lancaster’s website… www.harvestingrainwater.com
And another great post by Happy DIY Home: https://happydiyhome.com/how-to-harvest-rainwater/
No matter what climate you live in or what your rainfall pattern looks like, there’s likely a way you could be better utilizing that water and turning it into a valuable resource instead of letting it become a pollutant.