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Creating and Managing a Patch of Wet Grassland

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Marsh marigoldNot to be confused with a bog garden or a water meadow, which is a typically English, artificial, landscape feature, this article aims to give the reader enough information to recreate a small area of wet, species-rich grassland or wet meadow. Due to our tendency to drain large areas of land for agriculture and housing, we have lost many of our natural wetlands worldwide. This may contribute to erosion, loss of habitat and flooding.

When thinking about wet grasslands, images of sinking into mud and being attacked by flying insects from all sides while hopping from one clump of grass to another may come to mind. However, you can create a different picture! A wet grassland can help transform your garden into a wildlife paradise.

This article will guide you in the right direction and, with a little patience and time, you will soon be able to enjoy the pleasures of having your very own small patch of wet grassland. By using an existing damp area or simply creating one and adding native plants, you will attract many local insect and animal species.

Creating a wet grassland

A wet grassland does not, like a swamp, marsh or pond have standing water, except for during a few brief periods during the year. However, the soil in wet grassland is very damp and squishy, which is commonly compared to a soaked sponge, in much of the literature.

The first step in creating the wet grassland, is to find a location that will provide the correct levels of sunlight and moisture. The easiest way to do this is to take advantage of an already wet and sunny area in your garden. This could be a muddy area, a pond edge or an overflow. However, if none of these exist, don't despair as there are actions you can take to help water retention.

The steps taken to artificially create a small wet grassland area are similar to those used for creating a pond and its subsequent establishment and management would be similar to a perennial, wildflower meadow. Ideally, the shape would be irregular; a square or rectangle would not look natural. An easy method of delimiting your area would be to lay a length of hose or thick rope on the ground, so that any curves would look natural. The width of the area should be about 2m wide. When you are happy with the shape, it is time to dig your hole. Ideally, you'll create a dish shaped hole sloping to a maximum depth of 45-60 cm. Creating a smaller area could result in the soil drying out.

Cover the bottom and sides of your area with approximately 5cm of sand and line the inside with a good quality pond liner. Unlike, pond creation, where every care is taken not to pierce the pond liner at all, in this instance it is important to pierce the liner particularly near the top to allow excess water to escape; this may sound like a contradiction in terms but too much water can be as disastrous as too little. Err on the side of caution; it is possible to add more holes later, although it's much easier not to!

Prepare the soil you've removed when digging the depression, by breaking up any large lumps and remove large stones and root fragments. Sift some soil over the pond liner to a depth of 5cm and fill in the rest of the depression with your prepared soil. Prepare the surface, as you would for a perennial meadow by raking the surface to create a fine tilth. Take care to ensure that your new wet grassland is level with the surrounding area. Slowly, pour water into your newly filled area, too fast and you will create rivulets on the surface and ruin your careful soil surface preparation. The area should be perceptibly wetter than the surrounding area. If the area is too wet, i.e. too much water is being retained, stick a garden fork through the soil and pierce the liner some more. Leave the soil untouched for a few weeks, to ensure that dormant weed seeds have an opportunity to germinate in your area and can be removed before planting or sowing. Now is the time to keep an eye on moisture levels and adjust your drainage accordingly.

Plants for your wet grassland

The reason why the location of your wet grassland is of great importance, is because many grassland plants, adapted to high moisture conditions, require full sun for at least six hours a day. The soil for your grassland should be quite low in nutrients; you should never add fertiliser. A rich soil will allow grasses to become dominant and out compete the slower growing wildflowers. Newly replanted wetlands are very vulnerable to attacks from unwanted ('exotics', non native) species, and weeds which will spread and take over the area. The best way to keep these out of your wet grassland is to pull them out by hand, including the roots, as they attempt to colonize.

A few recommended perennial flowers

The plant species you select will be dependent upon the length of time the soil will be saturated or covered with water, depth of the water, the amount of sunlight on the site, the local climate, soil pH, and the size of the wetland.

  • Meadowsweet - (flowering season: June/September)
  • Cuckoo Flower - (flowering season: April/June)
  • Selfheal - (flowering season: June/November)
  • Ragged Robin - (flowering season: May/June)
  • Meadow buttercup - (flowering season: April/June)
  • Marsh bird's foot trefoil - (flowering season: June/August)
  • Yellow flag iris - (flowering season: May/July)
  • Marsh Marigold - (flowering season: March/June)
  • Two slightly larger wildflowers that could be successfully incorporated into larger wetland areas:
  • Meadowsweet - (flowering season: June/September )
  • Purple Loosestrife - (flowering season: June/August)

A few recommended grasses

Many grasses suitable for a wet grassland are quite large, such as Reed Canary Grass (Phalaris arundinacea), others will form large tussocks and shade out the wildflowers that you want to encourage, so avoid such species. For the purpose of this article which is only dealing with creating a small, wet grassland we suggest:

  • Common Bent
  • Red Fescue
  • Crested Dog's tail
  • Sweet Vernal Grass

In addition, sedges and Soft, Sharp-Flowered or Jointed Rush should be included. With proper management such species may colonise after a number of years as will a range of interesting mosses and you maybe lucky enough to even get some liverworts.

Before sowing or planting your wildflowers you need to make sure that the soil is moist, if not then soak the soil overnight, and sow the seeds or plant the following day. Use the method for perennial meadow creation.

Manage your wet grassland

The ultimate success of your wet grassland will depend on its management. Principally, management will be very similar to the perennial meadow, described here. It is important that the wet grassland is kept moist during dry periods. Ideally, additional water should come from stored rain water, however tap water will also do, if it has been left standing for 24 hours.

It may take up to three to four years, before your wet grassland finds its equilibrium, but once it has been established and been looked after properly, you will be rewarded with the joys of a low maintenance area of beauty as well as helping biodiversity.