When gardens turn into bogs, tackle the drainage problems before your plants succumb.
There is nothing like a quagmire of a garden to give you that bogged-down feeling. And it’s not only gardeners who get that sinking feeling; many plants will quickly turn up their toes in soil that’s too sodden too often.
There is no quick fix for garden drainage problems. The first step is thorough investigation. Before you try to take water away, you need to find its source.
By digging a hole you will be able to observe the water quality and get some idea of where it’s coming from. If the hole only fills up when it’s raining, then is slow to empty, it generally indicates poorly draining soil. If the water looks murky and the level doesn’t drop much, even when you attempt to channel it away, you’re probably sitting on a high water table or swamp. If it fills with clear water, you’re most likely in the path of an underground spring.
Trying to drain an underground stream will never work, so in such cases diversion is probably your best bet. If the water is from an underground stream, it tends to be clear and, although the ground might be mushy, will still smell fresh.
Poor soil quality in a swamp-like situation where water is not escaping means it’s likely to be stagnant, and there will be a putrid smell if you dig into the soil. This is the least desirable condition.
Once you’ve determined the water source, you need to consider the best solution. If it looks serious, call in a drainage expert. Water has a way of getting into places it doesn’t belong, and you don’t want to end up passing it from one neighbour to the next or redirecting it into the basement. It’s the sort of DIY you can’t afford to have go wrong.
If the volume of water is not great, you can achieve a lot with drainage coil, scoria and a large hole. Remember water flows downhill, so if you’re digging a channel, make sure there’s a slight gradient. Lie the drainage coil among scoria in the channel. If the area is large, you may need a series of channels, which should be evenly spaced to avoid wet and dry patches. A herringbone pattern is great for a lawn, with small, even channels running into the central “spine”, which, ideally, should be slightly deeper.
When channelling water, you need a collection point. The simplest is to dig a large hole at least 600mm square and a minimum of 300mm below the lowest point of the channel. Fill it with scoria, then a layer of permeable fabric, such as weed mat, before topping with soil. This creates a path of low resistance and a container for excess water until the water table settles and the water seeps back into the natural system.
If digging up the garden is not an option, there are plenty of attractive plants that will tolerate water and also act as natural water filters that soak up a certain amount of effluent. Of these, reeds are my favourite. With their range of hues, seedheads and linear texture, reeds make an attractive addition to most gardens, whether planted en masse or in combination with wet-loving perennials such as cannas, iris or zantedeschia. All three species come in a range of colours – from whites and soft pastels to hot subtropical colours.
Alternatively, for a green garden, you can combine reeds with Ligularia reniformus or Ligularia “Britt-Marie Crawford”, with their dish-shaped leaves. Along with their aesthetic appeal, reeds thrive in wet conditions, and are tolerant of moisture fluctuations. This is important because areas that may be flooded in winter can be dry in the peak of summer.
An elephant-eared taro is tolerant of wet feet and also makes a stunning contrast of form. For a situation that’s wet year-round, use real wetland plants such as the wonderful raupo, with its thick brown seed heads, which are also worth taking inside to use as floral arrangements.
When planting near natural water sources, stick to native varieties that pose no risk if they spread into waterways.
A great idea is to associate reeds with a water feature, and they’re especially effective around a swimming pool. Many contemporary pools use moats of planting to allow a clean view of the pool edge while ensuring safety regulations are met. A mass planting of reeds is the perfect solution, as it will fill the space and deter children from climbing through and into the pool. Engaging these natural associations, even in a contrived setting, makes for a convincing design.
However deep the bog of winter, there’s always a solution. With the right plants, it can become a pleasure of its own.