A Woodland Waterfall

Landscape Smart : Episode LDS-407 -- More Projects »
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A small mountainlike waterfall becomes a focal point for this garden.
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Figure A
With a bit of planning and one weekend of work, you can bring the tranquil ambience of a mountain waterfall to your backyard. To see how the professionals achieve such an effect, series host Ken Bastida visits the San Francisco home of Stanford and Margaret Gee to observe the work of Johan Kahlstrom, landscape designer and avant gardener.

Deciding where to put your waterfall is the first step, and Kahlstrom outlines a few basic considerations:

  • Find a natural focal point. The Gees pick a corner next to their new flagstone patio (figure A). The site should have sufficient height to tower above the plants around it.
  • For maximum enjoyment, place the waterfall where it can be seen and heard from indoors, typically near a window.
  • Choose a location that integrates well with existing surroundings.
  • The waterfall should be adjacent to outdoor seating.

    Though professionals will charge about $1200 for the project, you can do it yourself for around $500. You can also expect a medium level of difficulty; the physical labor is not too bad, but achieving an artistic, natural look with plants and stones requires some extra thought. With a clear plan in mind, you are ready to start work.

    Digging the Pond

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    Figure B
    Before you grab your shovel, mark the boundary of the pond with spray paint (figure B). The Gees' pond measures about four feet across and borders one edge of the patio. Digging to a depth of 20 inches is sufficient, but you need a minimum of 36 inches if you plan to include fish. After the excavation is finished, find the lowest point in the pond and dig an extra depression large enough to receive your recirculating pump. Kahlstrom also digs slightly underneath the flagstones to create the illusion of water disappearing underneath the patio.

    Shaping the Waterfall

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    Figure C
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    Figure D
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    Figure E
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    Figure F
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    Figure G
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    Figure H
    Create the foundation of the waterfall with soil excavated from the pond, building up a mound about two feet high. Next, add the main focal point by perching a large rock on top of the mound. Kahlstrom prefers to use "mock rock," a hollow, artificial rock that is light enough for two people to carry (figure C). He says that mock rock also looks real and creates a lot of height in a small space, an important consideration in achieving sufficient visual impact. Once the main rock is positioned, backfill soil around its base to help hold it in place (figure D).

    Digging out Details

    At the base of the main rock, create the upper bowl and spillway by digging a depression about four to six inches deep (figure E). About one foot below the spillway, dig out an inverted v-shape on the edge of the pond to provide an inlet for the falling water (figure F).

    Finally, around the rim of the pond you need to dig out a narrow shelf to be used for placing plants and smaller rocks (figure G). Also be sure the shelf is level for a perfect look.

    Placing the Line

    Use a single piece of standard, flexible pond liner, making sure that it's large enough to fit loosely over the entire waterfall and pond. Tuck the liner against all surfaces and pleat it where necessary to conform to the various shapes and voids (figure H). When the fitting is completed, fill the pond with water to keep the liner weighted down.

    Adding Smaller Rocks

    Kahlstrom recommends using indigenous stones to build up the remainder of the rock structure. He also says it's good to find stones with bits of moss and lichen that will continue to grow after the water is added, thereby creating a more natural look.

    Begin building the upper level by positioning the spill stone. Place a flat moss rock in the upper bowl depression, and then pull a bit of the liner over the back edge to keep water from flowing underneath.

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    Figure I
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    Figure J
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    Figure K
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    Figure L
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    Figure M
    Place additional rocks along the back edge to hide the liner and hold it in place (figure I). Continue building up rocks around the spill stone to create the upper bowl and the sides of the waterfall, backfilling behind each rock to prevent movement. Gaps between stones aren't a problem because they can be used later as space for plants. As you pile the rocks, lay the tubing that will recirculate water from the pump system (figure J). The tubing at the top of the waterfall can be hidden between rocks; the remainder can be buried later.

    Start assembling the lower level by positioning another flat moss rock under the spill stone to cover the base of the spillway. Continue building the lower level by adding field stones along the shelf at the edge of the pond and at any other places the liner is visible. With the liner covered, the main structure of the waterfall is complete (figure K).

    Finishing Touches

    Use small river rocks (figure L) to suggest the look of an ancient stream bed and to fill in places where the liner still shows between the larger rocks. You don't need to be precise; just take a shovel and let them fall randomly.

    For this project, Kahlstrom used a recirculating pump with a flow rate of 530 gallons per minute to really get the water cascading over the rocks. Simply attach the lower end of the tubing to the pump discharge opening and sink the assembly into the recess at the bottom of the pond (figure M). After testing to assure proper operation, adjust the water flow over the spill stone.

    Adding Plants

    Kahlstrom offers two guidelines for your planting scheme. First, use lush plants typical of the growth seen around waterfalls. Second, use the principle of forced perspective: by placing large-leafed plants near the front, plants with similar, smaller leaves in the middle, and plants with even smaller leaves in the back, you create the illusion of a larger mountain and waterfall. Behind the waterfall, Kahlstrom uses woodland plants with interesting forms and foliage to draw attention, and in the very front he places small, fine-textured plants with jewel-toned blooms to bring color to the area.

    To get you started, Kahlstrom suggests specific plants for the various locations.

  • Japanese maple (Acer palmatum 'Ever Red', for Zones 6-8, hardy to -10 degrees F). Place near the top of the waterfall.
  • 'Tricolor' sedum (Sedum spurium, for Zones 4-9, hardy to -30 degrees F). Good for gaps between field stones and native to woodland areas, sedum's mat-forming growth pattern is perfect for borders and rock gardens.
  • Japanese blood grass (Imperata cylindrica, for Zones 4-9, hardy to -30 degrees F). This grass is favored for spiky foliage that turns from green to a striking blood red, and the long blades are a graceful accent to a breezy garden.
  • Dwarf geranium (Geranium cinerium, for Zones 5-9, hardy to -20 degrees F ). Popular for woodland gardens, it is a compact, low-growing perennial with small, brightly-colored blossoms that serve to brighten up dark corners.

    Special Effects

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    Figure N
    To create a misty effect typical of real waterfalls, add microspray nozzles to your drip irrigation system (figure N). Adjust the nozzles to their finest spray setting and place them around the falling water. This addition will also help replenish water loss caused by evaporation.
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    Figure O
    With the waterfall placed at a focal point, it becomes a useful source for tying together other elements of your landscape scheme. Here, the undercut pond seems to flow beneath the flagstones, so Kahlstrom creates the appearance of a dry creek bed exiting the opposite side of the patio (figure O). This in turn produces an illusion of a larger waterway and provides an opportunity to unite the rest of the yard by means of a meandering wet-weather stream flowing through it. The creek bed eventually disappears into a fern grotto on the opposite side of the yard.

    Just give your imagination room to run and you can create a garden waterfall that reflects your personality and suits your needs.

    Resources
    manufactured boulders
    Second Nature
    P.O. Box 217
    Alamo, CA 94507
    Phone: 925-943-6333
    Fax: 925-943-3027
    URL: www.2ndnatr.com
    Guests
    Johan Kahlstrom
    Landscape Architect
    The Avant Gardener
    3871 20th St.
    San Francisco, CA 94114
    Phone: 415-824-0936
    E-mail: avantgardener@aol.com
    Website: www.avantgardener.org
    Also in this Episode
    Landscape Smart : Episode LDS-407
    •A Woodland Waterfall