It stands to reason, therefore, that when soil is overtly boggy or flooded with water for any extended period of time, plant roots will be starved of oxygen and will begin to break down and rot, ultimately killing the plant.
One way to deal with the issue of poor drainage is to select plants that thrive in boggy conditions, but this severely limits our choice, and often poor drainage impacts on our garden in other ways – boggy ground can become unpleasant to walk across, may adversely affect surrounding hard-landscaping materials (rotting wood or making paths slippery) and in extreme cases, when pooled water becomes stagnant, it may result in an unpleasant smell and breeding ground for pests and diseases.
What to do?
The first step when addressing issues of poor drainage within the garden is to determine exactly what is causing the problem. Initially, assess the lie of the land (literally) – both within your garden and the surrounding topography.
Water runs downhill so any area of ground at the base of a large hill or in a valley may have a higher water table – often resulting in permanently boggy ground.
This is the hardest problem to solve, especially when it occurs across a large area, and in this case it might be the best option to raise plants well above the boggy ground by installing raised beds (photo 2) or, on a larger scale, introducing higher areas of ground within the garden by creating a series of terraces with low retaining wall.
Down the drain
Another option might be to channel underground water away from plants by installing some type of drainage system – especially useful if water can be directed to another area within the garden where it’s actually of benefit – perhaps directly into a natural pond.
Perforated plastic drainage pipes can be purchased at most DIY stores – these allow water to seep into the pipe and then water is carried away. Pipes like this are very effective, when laid correctly, but over a large area can be costly and labour intensive to install. As with all major construction jobs, it may be advantageous to call in an expert – even if it’s only for advice.
On a smaller scale, other materials can also be used to created drainage channels including trenches of coarse gravel (over which a layer of topsoil is placed) and even reclaimed terracotta pipes (photo 3).
Sometimes the problem is more localised and easier to solve and may just boil down to the nature or condition of your soil. Clay soil is made up of finer particles (as opposed to the coarser, better-drained, sandy soil), and these fine particles may become compacted over time, resulting in less space for water to drain away – the good news however, is that clay soil is the most naturally nutritious and with a little bit of attention it can be turned into ground where most plants will thrive.
First step is to get the soil aerated and the one of the best ways to do this is, especially in an area where you intend to establish plants, is by digging in plenty of well-rotted organic matter in the form of compost (photo 4). This will not only ‘open up’ the soil, allowing water to drain away and supplying the much needed oxygen to plant roots, it will also increase the nutritional qualities of the soil. Though in many instances compost is best, a heavily compacted soil can also be opened up by digging in other organic material such as coarse grit, straw, sand, or even broken-up bark and sawdust (ensuring it comes from untreated wood).
Soggy lawns and wet walkways
When an area of poor drainage occurs on a small section of lawn, it may be enough to aerate the underlying soil with the tines of a garden fork (photo 5) enabling the water to drain away. Alternatively, another option may be to level any dips in the ground, where water may puddle, by building up the ground level with a layer of topsoil before reseeding or turfing.
Often part of the underlying problem with areas of access is that constant foot traffic will almost certainly compact any bare soil into a hard impenetrable surface, on which water will pool and turn soil to mud in winter months.
Help to alleviate this problem by creating designated paths and walkways within the garden to prevent excessive foot traffic on areas of bare soil or across the lawn – improve drainage even further by using a material such as gravel or crushed shells to create well-drained walkways (photo 6). Similarly vehicles will quickly compact soil in driveways or parking areas (even if it’s grassed) so treat these in the same way, providing a sturdy paved or concreted surface on which vehicles can drive and park.
Paved or concreted walkways and patios need to have a ‘run off’ to direct rain water onto areas of planting or lawn where it can drain away, but in some instances this isn’t possible.
This needs to be figured into the equation when planning paths or patios, and so it might be worth considering installing a drain if necessary.
Another option is to create a channel alongside the path to carry water away (photo 7).
If there’s no escaping the fact that your garden is wetter than most and drainage will be an ongoing issue, then it might be time to embrace this fact and choose plants that thrive in these conditions and hard-landscaping materials which will respond well in appearance.
Damp conditions encourage the growth of moss so consider weathered natural materials such as reclaimed bricks or old weathered sleepers when building raised beds (photo 8).
If certain spots in your garden are prone to drainage problems, raised beds and planters may be the answer for plants, but to create an attractive area of flat ground, consider a simple timber edging to act as a retainer for a layer of stones or gravel (photo 9) – do, of course, remember to lay weed mat down first though, because no matter how poor the drainage, some unwanted plants will always grow through!