Creating a Bog Garden
Although very few gardens contain marshy ground, it is not difficult to replicate these conditions artificially. In this damp environment a rich selection of moisture-loving plants with bright flowers and luxuriant foliage will flourish, even in the height of summer. Ponds and bogs are complementary garden features. But an area of water is by no means essential and a bog garden can work extremely well in its own right. Constructing a bog garden is similar to, but simpler than, making a pond. It basically consists of excavating a hole, lining it with a waterproof membrane and filling with enriched soil.
Siting a Bog Garden
The ideal site for a bog garden is in partial shade, as this enables you to grow the widest variety of plants. This may not be possible if you are making one in an open area next to a pond.
Fortunately, many plants, such as astilbes and hostas, recommended for shady situations, will tolerate a greater degree of sun, particularly in cooler areas of the country, if they grow in soil that is never allowed to dry out. Bear in mind that a bog garden in sun means more watering, and feeder ponds will need frequent topping up in summer.
Adjacent to a Pond
From a practical point of view, siting a bog garden next to a wildlife pond means the overspill from the pond should keep the bog garden soil moist. There are wildlife benefits too, as many creatures like to approach the water under cover and also love a damp, leafy environment. Aesthetically, the lush foliage of many bog plants creates a natural visual transition from water to dry land and successfully integrates a pond into a surrounding garden.
Ideally, you should build a bog garden at the same time as the pond, though it can be added to an existing pond later. A layout with bold, flowing curves looks in keeping with an informal pond. Make the bog garden's size no greater than the pond, to keep the features in balance.
A Stand-Alone Bog Garden
Without the constraints of a pond, a stand-alone bog garden can transform a dank shady area for much of the year with plants like candelabra primroses, irises and luxuriant ferns. Its success depends on careful placing. Although a position in light or dappled shade is desirable, if your garden is even slightly sloping, you should site the bog in the lower part of the plot where water would gather naturally, even if it is in the sun. This situation will look more convincing than on higher ground, and will collect more rainwater.
Watering a Bog Garden
A feeder pond helps to keep the soil in the bog garden saturated. Without an adjacent pond, frequent watering is essential. One of the best ways to make the task less arduous is to tap into the guttering that collects rain from a nearby building. If the catchment area is small, such as the roof of a shed or greenhouse, you could extend the downpipe to empty directly into the bog garden, via an excavated channel in which the extra length of pipe is sunk. A large roof could provide too much water, in which case it would be preferable to install a water butt or two to collect the run-off. Connect the butts to the bog garden with a hosepipe, which can be turned on as required.
Water a bog garden gradually rather than in a huge flood. An easy way to ensure the whole area is thoroughly but gently watered is to lay a soaker hose (also known as leaky pipe) around the bog garden when it is being planted. Hide the hose with a layer of mulch.
Choosing Bog Plants
Bog gardens are ideal for a wide variety of perennials: select them to give a succession of color from early spring to the end of autumn. Select some plants for their long-lasting foliage interest, to contrast with and provide a background for the flowers. Include some ornamental grasses and sedges (Carex) to bring light, airy touches. Choose plants that are in scale with your bog garden, as they range from dainty dwarfs to huge, spreading giants.
Shrubs and trees are unsuitable for artificial bog gardens as their root systems are large. In the long term they could penetrate and damage the liner. Where a nearby framework of larger plants or those for winter interest is required, the answer is to choose those that thrive in ordinary garden soil, but are in keeping with water. Look for arching stems and bold or feathery foliage, such as shrubby willows (Salix), dogwoods (Cornus alba varieties), bamboos and tall ornamental grasses, such as Miscanthus sinensis and Stipa gigantica. Plant willows and bamboos about 2.5 m (8 ft) from the edge of the bog garden so their roots do not damage the buried liner in their search for moisture. Dogwoods and grasses can be planted a little closer.
Routine Care
The maintenance of a bog garden is similar to that of an ordinary border. You need to keep on top of weeds and to deadhead flowers regularly to encourage more blooms. Cut back dead foliage at any time between autumn and late winter, but in cold areas delay this until early spring, as the dead foliage will give the rootstocks extra protection from frost.
Every year in early spring mulch the bare ground between plants with an 8 cm (3 in) layer of rotted garden compost or composted bark. At the same time feed the plants in bog gardens next to a pond with slow-release fertilizer pellets. While you can use other garden fertilizers in standalone bog gardens, their use near ponds presents a risk of surplus nutrients washing into the water, encouraging the growth of algae and blanket weed.