Up the road from me the local authority has recently constructed a new secondary school. Walking past post-completion I have many times admired two small gardens at the back of the school. Took me a while to understand that I was actually looking at rain gardens. How ingenious (and rather modern) to let the gutters from the roof spew rain water into these oases before (if) it continues down the storm water drains.
The purpose of a rain garden is to collect rainwater runoff, allowing the water to be filtered by vegetation and percolate into the soil recharging groundwater aquifers. These processes filter out various nasty pollutants. Rain gardens are effective in removing up to 90% of nutrients and chemicals and up to 80% of sediments from the rainwater runoff. Compared to a conventional lawn, rain gardens allow for 30% more water to soak into the ground. It’s important to note that rain gardens are NOT a water garden or a wetland. They are actually usually dry, draining within 12-48 hours.
Are you interested in incorporating a rain garden into your garden design scheme? If so I refer to the Groundwater Foundation’s design advise. They know this stuff more than I do. In short, however, rain gardens should be constructed on the downside of a slope and native vegetation is recommended. The massive benefit of the latter is, in addition to all of the above, that after the first year maintenance is usually minimal. Sounds pretty sweet to me. In the gardens that I refer to in this post the blooms start of with hyacinths, then comes the tulips, the nepetas, the geraniums, the Knautia macedonicas and the Alchemilla mollis. Which ensures that flower power attracts from March to late October (in Gothenburg, Sweden).
