Slow Drainage for Gardens and Dealing With the Drought

Most of France is expecting a severe drought. Despite no official declaration as yet, many farmers have had to roll their fields to prevent a dust bowl effect, some rivers now have irrigation restrictions and most others are seeing extraction rates already exceed what is sensible.

The one landscape, which is proportionately much smaller in France than in England is the garden landscape and the potagers’ and allotments are likely to be much more resilient against the drought than most other gardens. The same is true in the UK where there are very old allotment plots.

The most ancient of techniques are found here, many of which can be found across the globe as a standardised systems of slow drainage and irrigation. At least one universal traditional and simple system has been designed in plastic by an American firm with patent – this is a sad and frankly callous abuse of a global problem.

One huge factor separates much of the popular advice with regards watering in times of drought and the reality of the situation: We must concentrate on the soils – not the plants.

Slow drainage principles are simple and are often little more than ensuring drainage is at less than 3⁰ and that plenty of silt traps (maintained) are included. But this doesn’t fit in a small garden.

The ‘vertidrain’ or mini soakaway is the one of the best little tricks in any garden situation. Not only does it trap water run off and take it to ground, but it also allows for oxygen to reach sub soil, (vital in times of drought) and also can help mitigate against sub surface consolidation. It also helps alleviate problems with clayey soils as well as helping to ‘anchor’ urban trees as secondary root systems often head to the vertidrain and if positioned well this allows for a symmetrical root displacement.

A vertidrain is nothing more than a hole 30cm in diameter and at least 40cm deep and backfilled with stone.

It should however remain a job to be carried out by professionals as the location of the drain (under the drip line of a tree – or in grid form in beds) is subject to many factors – the slope of garden, existing vegetation and most importantly not damaging the secondary root system.

 The vertidrain can also be used very effectively during a drought for grey water use. Acting as a filter and enabling watering by bucket during the day. Again the positioning of the vertidrain is crucial – trying to maximise the effectiveness of the watering whilst also ensuring that grey water is ‘filtered’ properly.

One vital element in using grey water is to ensure clients or anybody planning to recycle their water does not contaminate the water first. With the plethora of ingredients now found in modern toiletry products this is easily done – thus reverting to natural soap and simple toiletry products is essential.

The vertidrain has permanent function slowing and trapping surface water run off and this must be also considered when positioning. The flow surface water takes is usually very noticeable in all gardens and the vertidrain and / or a series of vertidrains is a vital first step in preventing flooding in a surburban landscape. Of course the flow routes of surface water are frequently matched with water displacement across the garden.

An additional benefit of vertidrains is to alleviate problems caused by the toxic aquifers - very thin moisture layers that occur sub surface, (much more frequent in urban soils), that rest and accumulate all kinds of nasties and become a sludge that can drain as it is pooled above a sub surface consolidated surface. This can be sub surface infrastructure or sometimes the result, as is increasingly common with the rotovator obsession, caused by good intention by using machinery.

One factor we must all as professionals get used to is a porosity test of the soils. Simply filling a hole and timing how long it takes the water to disperse gives us vital information as to the state of the soil – which in most modern gardens does not reflect the soil type.

Reading through much of the ‘advice’ given in gardening media belays the reality of the situation we are facing in Europe with drought. This situation has been warned about for almost 30 years and still the general media take it as a shock and the water companies simply haven’t provided. And some ‘solutions’ being touted are sometimes not proven and sometimes could make the situation worse – for example the statement ‘a tree can take as much water as it is given’ is false, tree roots – indeed all plant roots require oxygen. Watering is a skill and should not be taken lightly. It is a skill that remains in the hands of gardeners, arboriculturists and landscapers and whilst we can help clients and the wider public to effectively water their soils – it is basically up to us to ensure where and when we can that watering is as effective as it possibly can be.

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Tags: drought, soil, vertidrain, watering


PRO Member
Comment by Stuart @ Eco Garden Maintenance on April 4, 2012 at 8:30

Another interesting and thought provoking blog from you, Pip. I'm situated in the vale of York on the east of the pennines and much of the rain has already been dumped on the hills before the clouds reach us. Most of the lawns around here go brown in summer due to lack of rain, compaction and low organic matter levels.

I am seriously pushing techniques which try to minimise the effects of drought, the regular addition of organic matter being the main one along with rain water butts, soil aeration and mulching. I have recently (last september) top dressed some lawns with pure compost and hopefully we will observe the moisture retaining benefits before the year is out. It just so happens that these operations fit nicely into an organic system which is what i am trying to achieve where possible.

www.ecogardenmaintenance.co.uk


PRO Member
Comment by Pip Howard on April 4, 2012 at 12:23

Thanks for your comments Stuart - I am getting increasingly anxious with some of media attention given to dealing with the drought - from plastic flowers through to simply planting more trees, (the Woodland Trust delving into Agroforestry techniques - all well and good but I want to hear how these new trees are going to be watered!). The soil interface is the zone we should be concentrating on and as much organic material as possible left to allow the soil surface to remain a highway and not left to pan. If the water companies started to publish guidelines on the maintenance of gardens it would avert a huge disaster and the start of ecological black hole in the garden and urban landscape. How many of the 6 million trees for the Queens jubilee are going to be alive next year - not many and will the media care? probably not.

Comment by The Perfumed Garden on April 8, 2012 at 9:21
Yet another interesting piece Pip, giving me more food for thought.

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