Soil, Sun, and Climate
Before buying any seeds, plants, shrubs or trees, familiarize yourself with water quality and soil conditions around the perimeter of your pond. Terrestrial plants have varying soil requirements, and water and soil quality can affect aquatic species.
The terrain around a pond will often vary widely in moisture content and soil quality. In the space of a few yards the soil might range from a highly compacted gravelly embankment to a rich loamy edge or submerged mud.
Soil borings or some shoveling will help gauge soil quality and groundwater level; while you're at it, testing different areas for pH is also useful.
Make a sketch of the pond and the surrounding terrain to be landscaped, noting soil conditions, pH, and the sunlight/shade factor. Clay, peaty soil, loams, sands and gravels have differing influences on a variety of plants. Knowing your soils will help you select plants and trees that are likely to succeed in a variety of soil conditions.
Soils can sometimes be modified to suit a particular plant's requirements. Be especially careful, however, about increasing fertility with nutrients than can wash into the pond and trigger algal and aquatic-weed problems. Note areas that may be subject to periodic flooding, which various plant and tree species may not tolerate.
First Plantings Around a New Pond
After construction of the pond, your first task is to stabilize exposed soil. Use a conservation mix that combines a quick-sprouting annual grass with deeper-rooted perennials that take longer to establish.
The shoreland around the pond is likely to have been heavily compacted during construction and may contain a high percentage of clay, which is not especially conducive to plant growth. That's why the building process often begins with stripping and saving topsoil from the site, which is spread around the pond in the final stage.
Use a protective mulch of hay to prevent the topsoil and grass seed from eroding during rainfall. Because hay can also contribute weed seeds, some builders prefer to mulch with seedless straw or a biodegradable mesh fabric. Hay or fabric is especially useful on dam banks and other bare soil slopes.
Native wildflowers are another option for ground cover at this stage. It's rare to have such a large spread of bare soil, ripe for establishing a new plant regime, so why not natives? They give you the chance to reestablish indiginous plant communities; they are more appropriate to the setting than their cultivated, hybridized relatives; and as long as you select the right ones they are perfectly adapted.
Overcoming native weeds and grasses is one of the major challenges in establishing wildflower fields. Even freshly stripped or turned over-over shoreland soil contains vigorous, long-lasting weed seeds, and considerable effort is usually required to dispatch them and make room for selected wildflowers. Mulching, using cover crops, burning, and tilling are some of the techniques used to prepare for wildflower planting.
The dam slope is an area that may benefit dramatically from wildflowers. Embankment slopes can look artificial and bulky, even with a grass cover, and they are difficult to mow. Wildflowers are an attractive alternative, a cascade of color and texture to transform a monotonous green buttress into a living tapestry that changes colors through the seasons and, once established, requires little maintenance. The embankment top is another good candidate for wildflowers. Not only do the flowers provide a dazzling array of colors, but many of them attract butterflies and hummingbirds, and because they are not mowed, they discourage Canada geese. Contact a nursery specializing in wildflowers to discuss various species suited to your region and growing conditions, as well as preparations for seeding. Some wildflower seed mixes include the grasses you initially need to hold your soil together, as well as the flowers, which are slower to become established.
Plant trees or shrubs after a good grass or wildflower cover is established, to protect against erosion and retain moisture. Remember, planting trees (or allowing trees to grow) on a dam may threaten embankment integrity.
New plantings are more vulnerable to temperature extremes and heavy rainfall than established ones, and need special attention.
Planting is most likely to succeed in moist soils. Watering may be necessary. Other factors affecting success include planting season, amount of sunlight, and climate zone. Be sure to match new plantings to these local conditions.
Excerpted from Landscaping Earth Ponds: The Complete Guide, by Tim Matson (Echo Point Books Media)
Topics vary from month to month and provide great information when researching where you want to build a pond, or how to keep it clean. Other areas of interest are pond use for more than swimming, and how to keep fish happy in your pond.