Water Gardens, Summer 2002

By Bob Henrickson
      Why water garden? It can be very rewarding creating a new garden
filled with colorful flowers and interesting textures. Now imagine creating a new garden that provides both beauty and habitat for a variety of interesting critters. It's relatively easy and inexpensive to create a water garden habitat for pest-eating toads, frogs, birds and dragonflies. Make your backyard a haven for wildlife while you relax and enjoy the soothing sounds of water splashing down your waterfall. A well-designed and maintained water garden will invite a plethora of wildlife to reward you with years of enjoyment.
There are so many fascinating plants that you can grow in the water that really can't grow anywhere else in the garden. It will challenge your design skills to create a natural look in and around your pond using plants, rocks and driftwood. Building a pond can seem rather complicated and often an expensive kit is used when installing a water feature to ease maintenance and improve water quality. You will be surprised at how easy it can be to install and maintain your pond without all the expensive extras. If you install a naturally balanced ecosystem that works with Mother Nature, not against her, you will create a winner.

Site Selection

      Try to locate your pond on a relatively flat area where it gets six or more hours of sun per day as most water lilies and marginal plants will bloom sparingly in a shady situation. If you don't have such a site, rest assured that it is possible to have a very attractive pond in a shady nook. But don't put your pond directly beneath a tree as roots may puncture the liner and having leaves fall into the pond will affect water quality. Avoid locating the pond in the lowest part of your property because the pond will collect debris and chemicals during periods of rain that will alter the water quality. It also helps to make sure the pond will overflow to desired areas during periods of heavy rain. Determine where you would like the water level to be and alter the surrounding grade so rainwater drains away from the pond and any buildings. Make sure to amend the soil that surrounds your pond edge to provide a good base for plants.

Construction

     Make the pond as big as you can because the more water you have the less the water temperature will fluctuate. A kidney bean or thumb-shaped pond has gradual curves and corners for a more natural appearance and easy installation of the pond liner. Try to keep the pond size in proportion to other landscape features; how much you want to spend on a liner; and how big a hole you can dig (or afford to pay someone to dig). Keep in mind that most people who have discovered how creative, interesting and fun water gardening can be usually wish they had made it bigger.
The two standard options offered by water garden suppliers are flexible liners and rigid liners. Rigid liners are more expensive and difficult to install. It can take some pretty fancy digging and backfilling to make the rigid liner rest evenly in the hole. Flexible liners are cheaper and will conform to a hole of any shape. Some water gardeners have used 45ml rubber roofing for the liner at half the cost of similar material from pond suppliers, reporting no adverse effects on plants or fish. Remember to add the depth of the pond to the surface area of the pond in determining the final size for the liner. Your pond should be deep enough so that it doesn't freeze solid in the winter. You generally don't have to go more than 24-30" deep to provide an ice-free area in winter for goldfish and potted plants.
     Lay out the shape of your pond-to-be with a garden hose and mark the boundary with some paint before removing any existing sod with a sod cutter. Now drive wooden stakes at 2' intervals outside the boundary and tie string on the stakes at the desired water level to periodically check the depth of the pond as you dig out the center portion. Mark the desired water level with a notch in the stakes to hold the string in place. Stretch the string across the pond to check on the depth by simply measuring down from the level string to the soil level.
The sides of the pond should slope gently outward, down to an underwater ledge at a depth of 12" or so. This is where you grow marginal or bog plants in pots resting on the ledge with 1-2" of water above the rim. The ledge should be at least 20-24" wide to accommodate a grouping of plants rather than a single row of pots.
     You will be surprised at how fast this area can fill with plants given the abundant native and exotic selections available in the trade. The gentle slope of the sides provides resting areas for flat rocks or driftwood and the shallow water becomes an inviting bird bath or a place to root cuttings. You will expand the life expectancy of the liner indefinitely by covering it with rocks to prevent any solar radiation.
     You'll be surprised at just how much dirt will come out of that hole, so decide whether you're going to haul it off your property or, better yet, use it as a soil base for the waterfall you know you're going to want. Now continue digging out the center of your pond inside the ledge area down to 20" or so to create a second ledge. This ledge should be wide enough to support the large pots that water lilies and lotus will require. After leveling off the ledge you can dig down to 30" or so to provide an ice-free area in winter. You might consider hiring a backhoe operator to excavate the center portion of the pond after hand digging down to the first shelf. Mark desired depth and shelf base with spray paint and periodically check on depth as the operator is digging.
     Once the pond is completely excavated, you should put down an underlayment that provides a soft padding for the liner. Many water gardeners simply use a layer of sand or thick landscape fabric to protect the liner from sharp rocks, roots or other debris. Unfold the liner and center it as evenly as possible over the hole. Fill the pond with your garden hose; the weight of the water will push the liner into any contours. Stretch the sides to concentrate folds in only a few areas (don't worry, you won't be able to see them in your finished pond). Fill the pond to the desired depth and work to provide a clean, stable edge sloping away from the pond. Then overfill the pond to determine where the overflow area will be during a rainstorm. Keep in mind what materials you will use to hide the extra liner and to design the edge of the pond, including plant material, rocks, mulch, driftwood or even sod. Larger rocks placed in the foreground and smaller ones in the background will add to the perception of depth. In much the same way you can make your pond look bigger by placing fine-textured plants (ornamental grasses) as a backdrop and large-leaved plants (lotus or canna) in the foreground. Plan on leaving some open areas around the edge for viewing and for easy entrance for maintenance.

Pond Plants

     Plants are essential for a pond-they help clean the water and provide food and shelter for fish, wildlife and beneficial insects. Include a number of underwater or oxygenating plants to absorb nutrients that would otherwise be feeding algae. Simply pot up bunches of cuttings in very coarse sand, top with gravel and place in 6-30" of water. The recommended rate is 1-2 bunches per square foot of pond surface.
     Water lilies are easy to grow and do best when their crowns are covered with 6-12" of water. To winterize a hardy water lily, simply cut back the foliage after the first killing frost, then place the pot in the deepest part of the pond. Lilies should be planted in large pots and divided every other year to maintain vigorous plants.
     Marginal or bog plants thrive on shelves along the margin of the pond. Different plants do best at different depths of water, but start all your pots in shallow water first before gradually moving them to their proper depth (use bricks or cement blocks for temporary supports). Both lilies and marginal plants are shipped bare root and should be planted in large pots with average garden soil and the crown of the plant at the very top of the pot. Allow space at the top for a top dressing of pea gravel to prevent muddying up the water.
Plan on dividing pot-bound marginal plants every other year to encourage new growth. Try planting a couple varieties in the same pot to provide a horizontal and vertical element in the same area. Place groups of tall spiky plants next to understory plants for a natural appearance. Hardy marginal plants should survive the cold winter months right in the pond. After a killing frost some gardeners recommend placing the pots in the bottom ice-free zone for overwintering, while others simply leave the pots in place and have had success with survival of most species. Most non-hardy plants can be lifted in the fall and kept as houseplants in winter or allowed to freeze.
Floaters are plants that simply float on the surface of the pond with their roots dangling in the water. Floaters draw out extra nutrients for cleaner water, but can spread like crazy once established, so you only need to plant a few each year. Pond experts recommend that up to 60 percent of the pond surface be covered with plants to shade the surface. Water quality and clarity are easy to maintain with a good choice of plant materials designed to filter nutrients and reduce the sunlight necessary for algae growth. To maintain some areas of open water, simply pull out any extras and add them to the compost heap.

Pond Maintenance

     If you build your pond right and put in lots of plants your pond will be self-sustaining. In spring, algae thrive in alkaline conditions, turning the water green. As aquatic plants mature, the water will become acid and the algae coloration will diminish until the pond becomes clear. Usually your potted plants can be put into place on the shelf in April as you notice growth emerging from the pots sunk down into the depths of the pond. This is also a good time to divide any pot-bound plants. Non-hardy plants are placed in the pond after the last killing frost and grow quickly once the water temperature is warmer.
     In summer, maintenance usually involves pruning back aggressive plants to maintain an area of open water. And you may have to add water on hot days-up to 2" of surface water can evaporate on a hot day. In autumn, clear the pond of dead foliage and dredge out leaves that would otherwise decompose and release noxious gases. Sometimes it helps to lay a net over the pond if there are trees near the water. Aquatic supply companies offer expensive skimmers ($500) that remove debris off the surface, but it's not too difficult to use a simple net to skim the debris off the surface after windstorms or daily leaf drop in the fall. Don't clean out the muck that accumulates in the bottom of the pond as it helps balance the nutrients in the pond and provides shelter for developing dragonfly nymphs. Obviously, the most maintenance involved with a pond is moving the potted plants in and out of the pond since you don't have to water and weeding is rarely a problem.

Should you keep fish?

     The advantage of keeping fish is that they eat mosquito larvae, but they will also eat your dragonfly nymphs. When they aren't overfed, fish will feed on algae and nibble on floating plants. In fact, you shouldn't have to feed your fish at all. If algae blooms appear on the surface of the pond let it run its course. If it doesn't go away you probably have too many fish, you're overfeeding them or you need more plants to shade and filter the water. It's very hard to control water quality with only a few plants and often requires chemicals to control discoloration. Keep it simple and start with little feeder goldfish. They're pretty, they're easy to see and they'll survive in the pond right through winter.

Waterfalls

     There are a number of advantages to creating a waterfall system for your pond. Moving water will attract many more of our feathered friends than stagnant water, it will help to oxygenate the water and deter any mosquitoes from developing. Moreover, most submersible pumps will recycle the entire pond volume in less than an hour. Locate your pump in the pond on the opposite end of the waterfall system to ensure the entire water volume is recycled. House the pump in a pump box that allows water to flow to the pump but prevents large debris from clogging the pump intake. A simple cleaning around the intake at least once a week will prolong the life of the pump indefinitely. A 2-3" flexible pipe is used to plumb the water from the pump to the top of the waterfall and can be dug slightly underground outside the pond until it connects with the waterfall. It is also important to provide an electrical source nearby so an extension cord is not needed to supply power to the pump.
In terms of construction, a waterfall can be divided into a series of descending basins. Each stage of the cascade will provide an individual focus for the eye and will force the water to pause before falling, so that the flow leaves the spill edge with a constant velocity. Create overhangs with thin rock or slate so that water breaks cleanly from the spill edge and to amplify the sound of the falling water. The steps of the waterfall should be between 6-12" high for the sound and vertical movement of the water to be fully appreciated. Remember that the higher the source of the waterfall, the stronger the pump required to raise the water. The watercourse should be lined with a rubber liner and great care should be taken to make sure it doesn't leak or the water in the pool that is being recycled will gradually be depleted. Liberal sprinklings of gravel and river rock will give a textural contrast and make the basins large enough so water remains in them at all times. Aquatic supply companies offer "biological filters" or preformed plastic kits that become a waterfall with living bacteria inside to help clean the water. They are very effective but expensive, and you are limited in the size and shape of your waterfall.
     If you build a water garden it will soon become your favorite place to practice your gardening skills. But don't install a water garden if you can't check on it daily. Visit your pond for ten minutes of daily maintenance and you will be rewarded with a beautiful garden. After all the work is done, you can sit back on a hot summer evening with your feet in the water and a cool drink in your hand. The sound of water splashing against rocks and a resident blue jay catching a quick bath make all the stress of the day drift away. A pair of dragonflies zooms by seemingly happy in their new home and the bird feeders placed a short distance from the pond buzz with activity. You feel a sense of pride in the habitat you have created and wonder why you waited so long. Dream it, build it.

Plants for the Pond
Oxygenating Plants Description
Anacharis, Elodea canadensis One of the best producing oxygenators; lance-like leaflets.
Moneywort, Lysimachia nummularia Small rounded leaves carpet the water sides of pond.
Tape Grass, Vallisneria spp. Grassy foliage with tiny white flowers.
Water Milfoil, Myriophyllum spp. Delicate, fern-like foliage.

Floating Aquatic Plants (non-hardy)
Fairy Moss, Azolla caroliniana Thick lacy carpet of floating bluish-green foliage.
Salvinia, Salvinia rotundifolia Rather broad, pale green floating foliage on slender stems.
Water Lettuce, Pistia stratiotes Floating shell-like rosettes of pulpy leaves. Sun or shade.
Water Hyacinth, Eichhornia crassipes 'Major' Shiny dark green leaves with expanded psuedo bulbs.

Tropical Marginal Plants (do best with 2" of water over crown)
Egyptian Paper Palm, Cyperus papyrus Tall 5-8' stalks with tuft of long thread-like leaves on top.
Papyrus, Dwarf, Cyperus haspan var. viviparous A miniature Papyrus with round "mop" heads on 2' plants.
Society Garlic, Tulbaghia violarea 'Variegata' Cream variegation on Allium-like foliage; in or out of pond.
Sweetflag, Japanese, Acorus gramineus 'Ogon' Chartreuse and cream iris-like leaves to 6" tall. Zone 6.
Taro, Colocasia spp. Unique large leaves make for excellent center piece.
Umbrella Palm, Cyperus alternifolius Flat, grassy umbrella-like heads of leaves to 3-5" tall.

Tropical Marginal Plants (do best with 6" of water over crown)
Canna, Variegated, Canna americanallis Yellow stripes against olive green stems; orange-red flowers.
Parrot Feather, Myriophyllum proserpinaroides Delicate, feathery leaves form dense whorls; zone 6.
Sensitivity Plant, Neptunia oleracea Mimosa-like leaves spread gracefully; yellow feathery flower.
Water Poppy, Hydocleys nymphoides Thick oval, floating deep green leaves; light yellow flowers.
Water Snowflake, Nymphoides spp. Small heart-shaped, floating leaves; delicate white flowers.

Tropical Water Lilies (do best with 12" of water over crown) Nymphaea spp.
Trim back leaves in fall and store in peat moss in plastic bag where the temperature stays around 50 degrees,
such as an enclosed porch or garage. Many outstanding selections available. Will survive in pond's ice-free zone.

Hardy Water Lilies (do best with 12" of water over crown) Nymphaea spp.
Trim back leaves in fall after a hard freeze and sink pots to the bottom of the pond in the ice-free zone for winter.
Some water gardeners simply overwinter their lilies from their existing location on the shelf. Many varieties
available in various colors and shapes.

Hardy Marginal Plants (do best with 2" of water over crown)
Arrowhead, Sagittaria spp. Distinctive arrow-like leaves; white flower spikes to 2' high.
Bulrush, Dark Green, Scirpus atrovirens Attractive, round stems with delicate seedheads atop 4-5' stems.
Cardinal Flower, Lobelia cardinalis Fiery red flowers on 2-4' stems; enjoys very shallow conditions.
Marsh Mallow, Hibiscus militaris Plate-sized white flowers with red center; native hibiscus!
Horsetail, Equisetum hyemale Segmented stems offer unique bamboo-like leaves. A must!
Iris, Blue Flag, Iris versicolor Attractive foliage and blue flowers; does well in and out of pond.
Iris, Yellow Water Iris, Iris pseudacorus Broad, sword-like leaves; bright yellow flowers; aggressive.
Marsh Marigold, Caltha palustris Glossy, rounded leaves; buttercups in profusion; early dormancy.
Monkey Flower, Mimulus ringens Lavender-blue flowers all summer; shiny foliage to 2' h; Nice!
Prairie Cordgrass, Spartina pectinata Offers graceful backdrop with yellow fall color; aggressive.
Rush(s), Juncus spp. Nice selections from native and introduced; also for pond edge.
Sedge(s), Carex spp. Nice selections from native and introduced; also for pond edge.
Sweetflag, Variegated, Acorus calamus Nice creamy variegation on sword-like leaves to 3' h. In or out.
Water Plantain, Alisma plantago-aquatica Broad leaves and towering stiff stems with tiny white flowers; 3' h.

Hardy Marginal Plants (do best with 6" of water over crown)
Arrow Arum, Peltandra virginica Produces glossy, arrow-shaped leaves that are very fleshy.
Bogbean, Menyanthes trifoliata Interesting foliage on creeping root stalks; fringed white flowers.
Cattail, Typha spp. Nice dwarf selections recommended; Typha gracilis is awesome!
Floating Heart, Nymphoides peltata Yellow fringed buttercup-like flowers; floating heart-shaped leaf.
Hawthorne, Water, Aponogeton distachyus Dark green strap-like leaves; nice white late blooming flowers.
Lotus, Hardy, Nelumbo lutea Great concave leaves and huge yellow flowers; native, 3-5'h.
Rush, Pickerel, Pontederia cordata Finest hardy aquatic! Shiny foliage with blue flower spikes.

Herbaceous Perimeter Plants (for the outside edge of pond or in boggy soils)
Daylily(s), Hemerocallis spp. Long linear grass-like leaves complement pond edge.
Lupine, False, Thermopsis caroliniana Spikes of yellow pea-like flowers resemble lupines in spring.
Nodding Pink Onion, Allium cernuum Shiny green leaves; nodding pink to white flowers in summer.
Feather Reed Grass, Calamagrostis spp. Excellent selections for the pond perimeter.
Garden Loosestrife, Lysimachia spp. Many nice cultivars for the edge; 'Alexanders' is choice.
Houttuynia, Houttuynia spp. 'Plena' has dark green leaves; 'Chameleon' tricolored leaves.
Iris, Japanese, Iris ensata Beautiful linear foliage and charming flowers.
Leopard Plant, Ligularia spp. Stately yellow spikes set atop large dark green leaves.
Meadowsweet, Filipendula spp. Nice species selections; fern-like foliage; misty flower clusters.
Milkweed, Swamp, Asclepias incarnata Dusty pink flowers in summer on 4' stems.
Polygonum(s), Persicaria spp. Bright flower spikes and variety of attractive leaf colors.
Sea Oats, Northern, Chasmanthium latifolium A 3' grass with attractive flat-sided seed heads in autumn.
Spiderwort, Tradescantia virginiana Grass-like leaves complement the pond edge.
Switchgrass, Panicum virgatum Nice selections for the pond edge; 'Dallas Blues' is excellent!
Turtlehead, Chelone glabra Attractive, glossy leaves and showy pink flowers in early fall.

Woody Perimeter Plants (for the outside edge of pond or in boggy soils)
Buttonbush, Cephalanthus occidentalis Dark green, glossy leaves; round white flower heads; adaptable.
False Indigo, Amorpha fruticosa Tough, adaptable; like giant leadplant; 6-15' h; can be cut back.
Holly, Winterberry, Ilex verticillata Deciduous holly loaded with fruit in fall; 6-8' h.
Serviceberry, Amelanchier stolonifera Nice early spring flowers; delicious summer fruit; 4-5' h.
Sweetspire, Itea virginica Spikes of fragrant white summer flowers; red fall color; 3-5' h.
Summersweet, Clethra alnifolia Glossy leaves turn a nice yellow in fall; spicy scented flowers.
Speckled Alder, Alnus glutinosa Speckled bark; interesting catkins; handsome foliage.
Willow, Dwarf Artic, Salix purpurea 'Nana' Narrow bluish leaves and slender purple stems; 6-8' h.