Planning what types and how to lay out the plants for your pond can be one of the more challenging tasks involved in your pond setup, but if done correctly, can be one of the most rewarding. First you must recognize what style of pond you wish to keep: koi pond, formal pond, informal pond, water garden, or natural pond, or bog pond. All styles have their own guidelines to produce the desired effect.
Simplest of all ponds is the koi pond. While the koi pond may have terraced layers near the edges, the majority of the pond will often be 4- to 6-feet deep. Given this depth and the fact that the koi will eat almost all types of plants, very few plants are suitable for this style pond. Koi also require excellent water quality and this will necessitate a large, high-volume water filtration system. About the only way to maintain plants in this type of pond is to physically enclose the plants to prevent the koi from getting to them. This might require a mesh screen several feet above the water level to keep the koi from jumping over the enclosure to get to the plants. Marginal plants or floating plants in an enclosure can provide a little natural filtration and excess plants can be fed to the koi. Sometimes you can make a “bog” pond that drains into the koi pond, providing a great natural filter. This bog pond can have all sorts of bog and even marginal plants. While there is a recent trend toward large natural koi ponds with rock and gravel-covered bottoms, the majority of koi ponds are extra-deep formal ponds.
The formal pond starts with a geometric shape, and usually has most of its surface area free of any plants. It often serves as a reflecting pool as well as a pond. The key to the true formal pond is symmetry, in shape and form. If plants are part of the original pond plan, there should be several tiers around the edge at different depths. This will allow the use of marginal plants that require different depths of water. Ideally, the layout of the marginal plants will produce a mirror image. The marginal plants should be placed in containers to facilitate removal/rearrangement and to aid in dividing the plant as it outgrows its container. The square-bottom container works better than a pot for marginal plants, as it is much less likely to tip over in a storm or as the plant reaches its mature height. Most marginal plants can be trimmed to maintain a proportional height to the formal layout. Using marginal plants of different heights can produce a visual accent and using variegated varieties can provide color even when the plants are not blooming. Submersed plants will have little visual effect on a formal pond, as they are out of sight, mostly there to provide oxygen and absorb some of the waste products. The use of water lilies is problematic in a formal pond, as they tend to grow “free form.” However, if only a few lilies are used, you can still obtain symmetry to the pond. A better accent plant might be a lotus variety.
Planting the informal pond is just that, informal. There doesn’t have to be any set pattern, though the pond should have several tiers to provide different depths for the marginal plants and even newly planted water lilies. There should be at least one area of deep water to provide security for the fish. (In northern areas, this is the one section of the pond that will not freeze, and is generally at least 3 feet deep.) The lilies are usually the kings of an informal pond, covering up to two-thirds of the surface. Marginal plants are used to provide accent and hide the pond edges. Irregular-shaped rocks can also be used as a border. The informal pond is one that will allow the use of floating plants, but try not to cover more than two-thirds of the surface with lilies and floating plants. Many floating plants will multiply exponentially and need to be harvested on a regular schedule. Floating plants can be used in the early spring to provide shade and food for fish, and then be removed as the lilies start to grow and bloom. Remember, as the lilies mature, you will need to move them to deeper tiers. The informal pond will mix in nicely with a bog area and even most terrestrial plants.
About the only difference between an informal pond and a water garden is the lack of fish and a filtration system in the water garden. Water gardens allow the use of a more densely planted arrangement. The pond itself isn’t as deep as needed for fish, just deep enough for the lilies and lotus. A water fountain or waterfall can provide a focal point and provide a peaceful sonic tranquility. The water garden is usually either a freestanding arrangement with level ground cover surrounding it, or it blends in with terrestrial plantings. The water garden provides for unusual shapes and blooms not found in terrestrial plants and can become the focal point of the entire landscape.
The natural pond has many of the characteristics of an informal pond, but definitely has bog areas, possibly streams, and certainly terrestrial plants surrounding most of the pond. Large rock formations can be used and a stream bed with several shallow waterfalls will be a certain attention getter. The natural pond has a bit of a disorganized look and different plants invade each others spaces. It is best to try to include several different types of blooming plants to provide a continuous season of blooms. Fish aren’t a focal point of the natural pond, but it should be stocked with fish. (If you plan to use native fish, be sure to check with the local authorities regarding any regulations. And never release any pond fish into a natural body of water!)
While it is rarely set up as a freestanding feature, the “bog” pond can make a great natural filtration system for informal or natural ponds that contain fish. The bog is a shallow area that is filled with gravel/substrate to the water level. This area is planted with bog plants (the roots are in water, the rest of the plant above the water level) that will remove the waste products nitrate and phosphate as they grow. Bog ponds can also remove heavy metals, and in the wild, actually can detoxify industrial chemicals that enter the water system. The bog needs to be placed slightly higher than the water level of the fish pond. A low-volume water pump is used to pump water from the fish pond to the “top” end of the bog and then the water slowly flows through the bog back into the fish pond. If the bog needs to be located farther from the edge of the pond, a streambed can be used to direct the flow back to the pond. (You might want to add a second water pump that pumps to the head of the stream to increase the stream bed flow without altering the bog flow.)
Perhaps the biggest caution that should be pointed out is that no matter how big you make your pond this year, next year you will want a larger one!