Does the name bring to your mind exotic flowers blooming in rain forests? You couldn’t be more wrong! Rain gardens are simply plants that absorb rainwater pollutants.
Is every garden a rain garden? Definitely not. A rain garden is distinguished by certain types of plants that can be grown in it as well as by a substrate made of special layers of sand and gravel.
Plants that can be cultivated in rain gardens are known as hydrophilic (water-loving) plants. It means that their roots keep the waterborne pollutants such as heavy metals and protein-fat compounds. Such plants include, for example, Viola palustris (marsh violet), Eryngium campestre (field eryngo), Osmunda regalis (royal fern), and Iris pseudacorus (yellow iris). Not the whole garden must be planted with hydrophytes, however, it is recommended that at least 50% of rain garden plants have the source pollutants’ absorbing characteristics. It’s also important to grow perennial plants.
The structure of the rain garden substrate is designed in such a way so that the storm water can quickly infiltrate into the soil. The topsoil layers remain wet only for a short while after the rainstorm.
Rain gardens should be located in the immediate vicinity of the rainwater drainage source, that is near the end of a downspout or along a slanted roof so that there is no need to buy water supply piping.