Why create an urban wetland
This type of garden can be used in the same manner as a “rain garden” – that is, a garden that captures rainfall from the roof and channels it into garden beds and ponds. oaking use of rainfall in this manner reduces the amount of storm water running into our rivers, streams and harbours. It also reduces the impact of torrential downpours, by slowing and absorbing much of the runoff, and purifies toxins from roofing materials, so reduces toxins entering natural outfall areas.
Wetland strata
There are essentially four different types of plant in a wetland. oxygenating plants live submerged beneath the surface. Aquatics live with their roots permanently submerged and leaves above the surface. oarginal plants prefer shallow water or areas that are flooded periodically. oost also grow in ordinary garden soil, so long as it’s consistently moist. Bog plants live on the edges of wetland in moist soil, but also grow happily in ordinary garden soil.
Creating a wetland courtyard
A main pond and series of raised planter beds on varying levels can make up a wetland courtyard. Keep the design simple and use natural materials that are sympathetic to the subject. Fundamental parts of the garden include boardwalks and bridges or stepping stones for access around the garden, a good-sized deck area for relaxation and entertainment, and a pergola or shade sail for sun protection. Enclosing walls provide privacy, shelter and the option to create “living walls” using ferns and other suitable plants.
Pond areas
Watery environments can house the tall (but vigorous) raupo in the deeper areas. Jointed twig rush, giant umbrella sedge and purei can be grown on shallow shelves created on islands or around the edge of a pond. Plant them in water plant baskets using Dalton’s Aquatic Mix and sit them with water just covering the pot surface. Add native milfoil to the pond as an oxygenating plant and install a pump and a combination biological and UV filter system to combat algal growth.**
Raised planter beds**
Fill these beds with many different plants, from grasses to rushes, flax and swamp astelia, plus striking nikau and cabbage trees for height. Large plants will obviously require more root space and larger beds. Some plants may require more moisture than others and cascading plants can be used in higher beds. Raised beds need to hold moisture, yet drain through to prevent water stagnating.
Ideally the whole garden would operate as one system. Rain from the roof would be collected in the pond area, a circulating pump would carry water from the pond to the raised beds, and water from the raised beds would then drain slowly back into the pond through a silt filter. Raised beds need to be waterproof, but with drainage or seep holes. They also require a base layer of stones covered in permeable fabric to allow for drainage, whilst holding in the soil. This needs to be commercial aquatic mix or a combination of loamy clay and coarse sand.
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