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 stormdrains, 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 no 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 native plants 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 grown 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. 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 critters that depend on them, the rain
garden provides 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!