This week is Nebraska Wildflower Week. It is a celebration of wildflowers and native plants in the wild and their use in landscapes.
A newer trend in landscaping where native plants are being used is rain gardens.
Rain gardens are typically small, shallow gardens planted to native wildflowers and grasses. They are located where they collect (harvest) rainwater run-off, usually from downspouts, paved areas or sloped lawns.
The first thing people envision when they hear the term rain garden is a water garden or a stagnant pool of water for mosquito breeding. Neither is correct. Properly designed and installed rain gardens only have standing water for 12-48 hours after a rainfall, depending on the amount of rain. They are dry the rest of the time.
While rain gardens are shallow depressions intended to collect rainwater, they are located in well-drained soils and designed to maximize infiltration of water into the soil or to channel excess water slowly to the nearest outlet.
Because of how rain gardens function, plants used in them need to tolerate short periods of water inundation followed by longer periods of dry weather. In Nebraska, our growing environment is often one of short periods of rainy conditions followed by longer dry periods.
Many Nebraska wildflowers and grasses are already adapted to the growing conditions of rain gardens. This is one reason they are selected for rain gardens. Many of them, like purple coneflower, goldenrod, Liatris and wild geranium are already commonly used in landscapes and are readily available.
The main reason native plants are used is because they have deep roots that are naturally dying and regenerating. The deep roots and this characteristic of dying and regrowing creates channels in soil that increases infiltration into — and percolation of — water through soil.
The deep roots of native plants also filter pollutants rainwater may pick up as it flows over surfaces, such as pesticides, excess nutrients and motor oil from pavement. Once rainwater from a rain garden reaches the nearest outlet or groundwater, roots and soil organisms have helped to cleanse it.
Because of the way rain gardens are designed, a slight depression with gently sloped sides and low berms on three of the sides, there are actually three growing zones in a rain garden. This expands the list of native plants that can be grown in them.
Wildflowers, such as leadplant, purple prairie clover, Penstemon and Aster that tolerate dry conditions, but not periods of inundation or wet soils, can be used on top of rain-garden berms. Wildflowers, such as Chelone, blue false indigo, joe-pye weed, Heliopsis and Helenium that tolerate wetter soils and inundation, are used on the bottom of these shallow gardens.
Most properties and many landscapes are designed to drain rainwater away as quickly as possible. This, despite the fact when it rains in Nebraska the moisture is usually very much needed. When it does rain, we can make the most of this valuable resource through the use of rain harvesting techniques such as rain gardens. Rain barrels, cisterns, bioswales and porous hardscape are other examples of rain harvesting methods.
Contact Kelly Feehan, Extension Educator, at 563-4901 or e-mail her at firstname.lastname@example.org.