Bulletin #2702, Landscapes for Maine: Adding a Rain Garden to Your Landscape - #2702 long description
This graph compares the elevation of the land of a sunny rain garden from how the original slope was to how it looks after adding a rain garden, with a semi-transparent overlay of the two. The original land has a fairly constant slope that descends by 1 1/2 feet in a space of 24 feet. With the addition of the rain garden, the land has been modified so that the slope descends by 1 3/4 feet in the space of 12 feet, and then rises up to the berm which peaks 1 1/4 feet above the low point of the valley. At that low point has been laid a one-foot depth of permeable mix that thins out to disappear at the peaks on the both sides of the depression. The berm falls to the same height as the original slope at a distance of 28 feet. The slope of this land has been exaggerated.
This diagram shows the measurements of a sunny rain garden that has a total diameter of 20 feet. It is arranged as three concentric circles, with a wide low center and two thinner outer rings at diameters of 2 feet and 1 foot 6 inches, respectively. The berm is a half circle and comprises half of the outermost ring, on the side farthest from the building. The slope of the land travels downward away from the building. The swale runs into the garden from a gutter spout on the corner of the building, and flows in on the side opposing the berm.
This diagram shows a sample arrangement of plants and fixtures for the circular sunny rain garden above. The swale runs 14 feet from a gutter spout on the corner of the building and flows into the garden on the side opposite the berm, at ten o’ clock on the circle. At eight o’ clock on the circle, an underground water pipe runs into the garden from the other corner of the building. There are two clusters of rocks: one where the swale meets the rain garden, and one on top of the place where the underground pipe drains into the garden. The inside of the garden is arranged as follows. In the very middle is Iris versicolor. It is surrounded by, starting at the top and moving around in a clockwise direction, Clethra alnifolia, Eupatorium maculatum, Clethra alnifolia, Asclepias incarnate, the rocks above the underground pipe, Asclepias tuberose, and Lobelia cardinalis. In a ring around this inner portion, moving in the same clockwise fashion, is Helenium autumnale, Symphyotrichum novae-angliae, Lobelia spicata, Symphyotrichum umbellatus, Lobelia spicata, and Symphyotrichum novae-angliae, and Helenium autumnale. These plants on this half of the outer circle are surroundeed by the berm. Continuing on this outer circle, there is Anemone canadensis, Potentilla arguta, Geranium maculatum, the rocks that the swale drains into, and Caltha palustris.
This drawing shows a sample arrangement of plants and fixtures for an oval-shaped shady rain garden There is a garage in the upper left corner of the diagram with two large oaks next to it, and below these is the garden. The swale drains from the corner of the garage into the left edge of the garden, where there is a pile of rocks. The specific plants in the garden, as described in rows from left to right, are arranged as follows. The top row is Hamamelis vernalis, two clusters of Rhododendron canadense, Osmunda regalis, Comptonia peregrina, and two clusters of Ilex verticillata. The next row is Comptonia peregrina, Ledum groenlandicum, Onoclea sesibilis, Osmunda regalis, Lobelia cardinalis, and Onoclea sensibilis. The bottom row is Comptonia peregrina, Geranium maculatum, Aquilegia canadensis, Arctostaphylos uva-ursi, Geranium maculatum, and Ilex verticillata.