Woods Creek Wholesale Nursery

Rain Gardens

Rain gardens are gardens which take advantage of heavy rainfall and stormwater runoff. They are designed in such a way that the placement and selection of plants improves the overall drainage in your own yard, your neighborhood and the entire area where you live.  Although the concept is old in many parts of the country, it is a somewhat new idea to the Pacific Northwest.  Here we have enjoyed the great natural forests to slow and filter runoff, but with the onslaught of development, the many hard, impervious surfaces create severe drainage problems and threaten our natural waterways. Rain gardens are a part of a new approach to managing stormwater runoff called Low Impact Development (LID).

The basic idea is that the “sunken” garden captures the water that quickly runs off impervious surfaces, such as roofs, driveways, patios, sidewalks, etc.  An amazing amount of water can quickly wash into the stormwater drains, along with all the contaminants and pollutants that come with it. Most roofs are made with some petroleum products, as well as road asphalt.  Many have chemical treatments to reduce moss from the roofs and it all runs quickly into the drains. Also, the fertilizers and other unwanted chemicals that are used in landscapes often run into the storm drains, and eventually into our streams and rivers, and finally the ocean.

In a rain garden, the area targeted to capture the water should be a spot where the water naturally collects, or before that area so that the water can be slowed down before it reaches the lowest point. The soil mixture and the plant selection will provide a natural filtration system that slows the water, allowing the plants to take up and filter dangerous nitrogen and phosphates and chemicals in the run off. The rain garden is not designed to be a pond or a bog, but rather a filter system for the environment.

There are three tiers to a rain garden. The lowest point must be planted with grasses or plants that do not mind standing in water for a period of time, but can also take some drought once established (2 to 3 years, but need to water during very dry extended periods). The second tier is filled with plants that can take a lot of occasional water, but not inundated. And the third, or highest tier, will be filled with plants that can take more drought, but also don’t mind being very wet during the winter.

The garden is constructed in a specific manner using underground piping from the impervious surfaces (roofs, roads) to the garden, or even better, a ditch or swale lined with rocks or plants leading to the garden. The rain garden in its final stage is about 6 inches below the surrounding ground, so that the water soaks in and disperses below. The specifics for your rain garden (location and soil types) should be researched to make sure that the area is a good candidate.

You can have any number of rain gardens located in your yard to capture the various sources of runoff. Many times these gardens are planted with plants native to the area because they are sometimes more adapted to being very wet or very dry.  However, in the Pacific Northwest, we must be very careful in plant selection since many of our natives grow under the forest canopy and not in full sun. So, the choice of plants for the right conditions of light and shade is quite important. In fact, the plants do not have to be native, just hardy filters that meet the requirements of a rain garden.

In addition to managing runoff and filtering contaminants for our natural waterways and the critters that depend on them, the rain garden provides a habitat for beneficial insects, birds and other animals to improve the overall quality of our planet.

Please ask us if you require assistance in constructing or planting your new rain garden!

Thank you for your understanding.