Once you've chosen the type and style of your garden pond, the next consideration is plants for it. Do visit a garden center in your area that specializes in or is knowledgeable about aquatic plants. They will be able to help you make the right plant choices for your locale. Maintaining a healthy garden pond which is clean and clear, with the correct balance between water plants and algae is essential. The water plants will compete with the algae for nutrients. These nutrients come from the fish droppings and nitrogen from the rotting plant material. Algae growth can be kept in check by shading at least half of the garden pond to prevent the sunlight from encouraging algae growth.
There are many types of plants available for use in a garden pool. Considerations such as water depth, amount of sunlight and how each species relates to its surroundings need to be taken into account when choosing plant material. Both floating leafed and submerged plants are needed for a healthy garden pond and should be included in your selection. Water garden plants are called aquatic plants, because their life cycle revolves around water. Aquatics plants come in different types such as: emergent or marginal plants; submerged or oxygenating plants; and floaters, the so-called ground covers in garden ponds and marsh plants. (Tip: Only introduce fish in your garden pond once the oxygenating plants are established because the fish will destroy them as well as the balance in the garden pond.)
Submerged / Oxygenating plants
Oxygenating plants, or submerged plants are important as they are responsible for the food, shelter, oxygen and spawning medium for fish. Oxygenating plants are also commonly known as pondweed. They are anchored with coarse gravel in mesh containers and will grow quickly and establish roots if left undisturbed. Because they are fast growers and rarely protrude above the surface, they will need thinning in smaller garden ponds. These aquatic plants are important in maintaining the quality of the water in garden ponds. They produce oxygen for use by both plants and fish. By utilizing nitrogen produced from decaying plant material and fish waste products, they deprive algae of nutrients. (Tip: It is best to cage these plants if the garden pond contains fish which tend to forage on submerged plant foliage.)
Nine to ten bunches of oxygenating plants per square meter (5.8 feet square) of pond surface will be sufficient to keep a garden pond healthy. Following are a few examples of oxygenating plants that can be used in garden ponds:
- Hornwort (Ceratophyllum demersum) also known as Marestail. Dark green, non rooting plant that doesn't float or sink - just settles in the water. It will thrive in deep, cold and shaded ponds and will provide an area for fish spawning.
- Fanwort (Cabomba Canadensis) Dark green bristles on thin stems. Flowers mid- to late summer are white with yellow centers. It has bright green fan like foliage. Fish tend to use them to spawn and fry will find shelter in the leaves. Fanwort will grow in sun to shade in water that is 15 to 30 cm (6 to 12 inches) deep.
- Jungle Vall (Vallisneria sp.) also known as Wild Celery. This plant has linear green, ribbon-like, translucent, pale-green leaves. It will grow in shade, part-shade and sun in water that is 15 to 60 cm (6 to 24 inches) deep.
- Anacharis (Elodea Canadensis and Elodea crispa). Elodea or Anacharis is a very good producer of oxygen and forms sturdy stems covered with curled leaves with occasional white flowers on the surface. It is also a dietary supplement for fish.
- Pondweed (Potamogeton spp.) This plant has branching stems with long leaves and is larger-growing than the other types of oxygenating plants.
- Water Crowfood (Ranunculus aquatilis) This plant has very fine foliage underwater and lobed leaves on the surface. In spring it will bear small white flowers.
- Milfoil (Myriophyllum spp.) also known as Parrot's feather. This plant is a prolific grower.
Emergent / Marginal plants
Emergent plants are sometimes also called marginals or marsh plants. These plants are grown along the edges of garden ponds where the roots are attached to the muddy bottom and portions of their stems are above the water. Some of them are even planted in water up to a depth of 20 cm (7.8 inches). It is very important to choose the right plants to suit the size of your particular garden pond. Roughly one-third of the pond margin should be covered with marginal plants to have a balanced effect. Emergent plants are usually placed so that the top of the pot is at or barely below the water level. Bog plants are also considered to be marginals. There are many different species of bog plants with varying heights, textures and foliage colors that add height and drama to water gardens. Following are a few examples of emergent plants that can be used in garden ponds:
- Variegated Water Celery (Oenanthe Javanica) This is a hardy Marginal plant with leaves that are variegated with pink and white. It also has bare roots and grows between 15 and 30 cm (6 and 12 inches) tall. The planting depth is 0 to 15 cm (0 and 6 inches) in full sun to shade.
- Cardinal Flower (Lobelia cardinalis). This plant sports bronze colored foliage with red to crimson flowering spikes from mid to late summer. These are slender plants that grow to height of 90 cm (36 inches) and will tolerate between 2.5 and 5 cm (1and 2 inches) of water. This is a great plant for adding color contrast to water gardens.
- Dwarf Cattail (Typha latifolia). This is a small plant that reaches a height of 90 cm (36 inches). Walnut-size catkins. It can tolerate up to 15 cm (6 inches) water depth.
- Zebra Rush (Scirpus tabernae-montani Zebrinus) These plants have segmented stalks with horizontal green and white variegations. The Zebra rush can reach 60 and 120 cm (24 and 48 inches) in height.
- Horsetail Rush (Equisetum hyemale). Also known as scouring rush. This plant has dark green segmented stalks and grows to about 90 cm (36 inches) in height. It is a vigorous grower and spreader and will tolerate damp soil to 30 cm (12 inches) water.
- Water Canna (Canna americanallis variegate) This is a plant with leaves that are orange with yellow stripes. It is a true aquatic canna hybrid. Long slender spade-shaped leaves. It has beautiful spikes of brilliant colored flowers. The plant itself reaches 1.2 to 1.8 m (4 to 6 feet) in height and will grow in up to 15 cm (6 inches) of water.
- Pickerel Rush (Pontederia cordata) or Pickerel weed or arrow-leaf weed as it is also known. This is a lovely plant with glossy green foliage, bright lavender flowers. It is quite easy to grow in water gardens and will flower in autumn.
- Variegated Sweet Flag (Acorus calamus 'Variegatus as well as Acorus gramineus) This is a grass-like perennial with beautiful green and cream striped foliage that persists all summer. Leaves are sweet scented when broken. This plant does excellent in sun or shade.
- Black Magic Taro (Colocasia esculenta) which is also known as the Elephant ear. This is an incredible plant with dusty charcoal black leaves on dark burgundy to black stems. It can be classified as a tropical marginal plant. It grows to a height of between 7.5 and 15 cm (3 and 6 inches) and can be planted in water between 0 and 15 cm (0 to 6 inches). It will thrive in partial shade to shade conditions.
- Arrowheads (Sagittaria latifolia) This is a plant with attractive, green arrowhead shaped leaves. White blooms in the summer. It grows from 30 to 120 cm (12 to 48 inches) tall. Arrowheads will tolerate sun to part shade.
- Blue Flag Iris (Iris versicolor and other Iris spp.) These plants include the Louisiana iris, the Japanese iris and the yellow flag irises. This plant bears mixed blue flowers in June with grass like foliage. Grows from 60 to 76 cm (24 to 30 inches) tall and will tolerate full sun to part shade.
- Dwarf Papyrus (Cyperus isocladus) Also known as Sedge grass. This plant is a perennial clump-forming plant with a green grass like foliage with "starburst like" flower-heads that turn brown in the autumn. Grows 30 to 45 cm (12 to 18 inches) tall and tolerates sun to part shade.
- Water Blue Bells (Ruellia brittoniana) This plant has green grass like foliage that grows between 60 and 120 cm (24 and 48 inches) tall. It bears blue flowers in summer that is reminiscent of Petunias. It can tolerate sun to part shade.
- Cork Screw Rush (Juncus effuses) This plant has interesting twisted and curled stems and grows to approximately 60 cm (24 inches) tall and tolerates full sun to part shade.
- Gennera manicata is a deciduous perennial with enormous leaves and brown flowers.
- Water forget-me-not (Muosotis scorpoides). This is a spreading perennial with gorgeous light blue flowers during summer.
- Cat's Whiskers (Scirpus cernuus as well as Scirpus lacustrus) This is a densely tufted rush-like plant that would be ideal for smaller garden ponds.
- White Arum Lily (Zantedeschia aethopica) This is a lovely, outstanding marginal or emergent plant with lush green foliage and striking white flower spathes.
Deep water plants occur further from the edge, between shallow and deep water, are other emergent plants where roots are attached to the bottom, but have floating leaves above the water. These plants usually have their leaves floating on the surface of the water and are essential in the maintenance of the correct balance in the garden pond. These plants shade the water and prevent the sun from reaching the algae; they also provide shelter for fish and other small animals. Above all they are very ornamental and dramatic. These plants like to be planted up in a heavy soil without any organic material. (Organic material would only encourage algae to grow.) It is a good idea to make use of special mesh containers to plant deep water plants in. You should cover the soil surface with coarse gravel or small stones to prevent the fish from removing the soil. A good balance can be achieved by planting one plant for every 2.5 square meters (26 feet square) of pond surface. Following are a few examples of deepwater plants that you can use in deep water gardens:
- Water Lilies (Nymphaea spp.) These are the most beautiful of the water plants in my opinion. Flowers colors range from yellow, blue, white, and pink to red. There are many different varieties and some grow vigorously, while others require shallower water and a smaller area. For most the best water depth would be between 30 and 80 cm (12 and 32 inches).
- 'Red Flare' - A tropical night blooming red water lily with maroon leaves.
- 'Tetragona' - A hardy miniature white water lily with freckled leaves.
- 'Joanne Pring' - A hardy miniature pink water lily with green leaves and deep edge.
- 'Helvola' - A hardy miniature yellow water lily with freckled leaves.
- 'Hilary' - A tropical day blooming pink water lily with green leaves.
- Pondweed (Aponogeton distachyos) This plant has dark green, strap-like leaves and bears scented white flowers with black anthers. These plants will thrive in water that is between 20 and 60 cm (7.8 and 24 inches) deep.
- Golden Club (Orontium aquaticum). This is quite a versatile plant with white stemmed flower spikes with many tiny yellow flowers that appears in spring and early summer.
- Lotus is also a dramatic addition to a garden pond. Both water lilies and lotus prefer full sun.
- The 'Momo Botan' Lotus Grows to a height of 60 cm (24 inches) and offers rose blooms from late winter through spring.
- The 'Wan-er Hong' Lotus Grows to a height of 30 cm (12 inches) and offers white blooms from mid winter through spring.
Though most are not grown for their flowers, some like lotus and water-lilies, are extremely dramatic and a feast for the eye when in flower. Bog plants are available for those not able to locate their garden pond in sufficient sunlight to support plant growth. Some bog plants can survive in locations that have as little as three hours of sun and still provide interest to water gardens.
Floaters are not rooted in the soil, but are allowed to float freely above or below the water surface. They are not as effective as the oxygenators but do not require anchorage. Floaters enhance the display of water lilies and lotus as well as adding a finishing touch to the water garden. They are the so-called ground covers of the garden pond world. They may be restricted by a framework to prevent them from moving around or allowed to float freely with the breeze. This produces an ever-changing look to the water surface. Some floaters are very prolific and may need to be kept in check by scooping out excess plants on occasion. If you do not keep it in check you will soon find that they become pestful like a weed.
- Water Hyacinth (Eichhornia crassipes) This Amazonian plant has shiny green leaves with stems that expand into pseudo bulbs. It bears orchid-like lavender flowers. Long, bushy roots provide fish with a location for spawning.
- Water Lettuce (Pistia stratiotes) This is a free-floating tropical plant that resembles floating lettuces with more intricately patterned than common water lettuce and a better overall plant with a compact growing habit. It has a tuft of long fibrous roots that trail beneath the plant itself.
- Sensitive Plant. Creeping plant whose leaves close upon touch. Planting depth: 7.5 to 20 cm (3 to 8 inches). Full sun to partial shade. Yellow flowers in summer.
- Parrot's Feather (Myriophyllum aquaticum) This is a South American plant with pale green, finely divided, feather-like foliage. Roots provide spawning area for fish.
- Water Fern (Azolla spp.)This plant is also called the Floating Fairy Moss or Mosquito fern. The foliage is a lovely red to purple tint during autumn.
- Giant Velvet Leaf (Salvinia longifolia and Salvinia molesta) This plant is also sometimes called Kariba weed or Water-spangle. It is an unusual floating fern with pale green round hairy leaves.
Algae are another plant type that is found in most garden ponds. There are hundreds of species of algae that can grow in garden ponds. Generally algae attach itself to the sides of the garden pond and remain innocuous. Some species of algae, namely the dreaded 'blanket weed' can grow up to a foot a day under ideal conditions and can rapidly clog a garden pond. On the other hand free floating algae is microscopic and is what causes pond water to appear green.
Water gardens need a mix of aquatic plants to attain a balanced system. You need to ask yourself the following: What look do you want? Do you want colors and textures, tall or short, lily pads and flowers or a combination of all?