The erratic weather conditions we continue to face in the UK means waterlogged allotments have become a common sight.
Waterlogging isn’t just a frustrating experience when there are jobs to get done, it’s a potential death sentence for your crops and the soil in which they grow.
In the winter of 2015, I’d turned a corner in the development of our allotment garden. After six months of ineffective, disorganised cultivation of the overgrown patch, I’d set out a plan of action and progress was only a spade turn away.
Then it started to rain.
The rain continued for weeks. Every morning I looked out of the window and wondered if it would ever stop. There were many jobs to do on the allotment in preparation for the busy spring.
When the rain finally stopped, I raced to the plot and was horrified. The allotment was flooded. This wasn’t a garden, it was a pond.
What is waterlogging?
Waterlogging occurs when the soil becomes saturated. On our plot, the pooled water was an obvious sign but water doesn’t have to appear on the surface of the soil for there to be a potential problem with waterlogging.
When allotments are waterlogged, air pockets in the soil fill with water and the roots of the plants are unable to get oxygen. Carbon dioxide and ethylene also build-up as the plants are unable to respire in the saturated soil.
Most of the time waterlogging doesn’t last long enough for plants to die. However, if allotments remain waterlogged for a significant period of time, the lack of oxygen in the root area will cause the root tissue to decompose.
How to solve the problem of waterlogging
Waterlogging can be prevented by achieving two objectives: Aerating the soil and enabling drainage of excess water.
Consider your soil
The soil on our allotment is heavy clay. It can be very fertile for many crops, however, it needs to be managed well for this to become as the farmers say – Strong land.
Clay soil can become a sticky mass. It can become almost impossible to cultivate, and when it dries out it becomes as hard as cement. In wet conditions, the clay soil on your allotment can exacerbate the problem of waterlogging.
Clay soil needs to be improved for it to flocculate – this means the microscopic particles which make up the clay gather together in larger particles. To improve clay you have to get as much organic matter, such as manure and compost, into the soil. The result will be a soil that is more easily worked, drains better, allows air to get down into it and allows the roots of plants to penetrate it more easily.
Drainage
Land drains are an ancient but effective method for managing waterlogged ground. Creating drains can be hard work but you only need to do it once.
If your allotment slopes, you can drain the plot by digging a ditch at the top of the plot to cut-off the water running on to it and digging another ditch at the bottom of the plot to drain away excess water from the plot itself.
On most allotments, a ditch at the bottom of the slope should be enough. Traditionally, the ditch is filled with a few inches of gravel and a perforated plastic pipe is then laid along the ditch to guide the water away from the plot. More gravel is added to the ditch and then it’s backfilled with topsoil.
Our allotment doesn’t slope and so I’ve improved drainage using ditches to effectively lower the water table around the beds. This was achieved by digging out a network of paths and backfilling the paths with wood chips. The soil from the paths was then used to raise the level of the beds. It’s been hard work but it works.
Raised beds
Raised beds are an intensive strategy for the management of waterlogged allotments but are very effective.
As well as the prevention of excess water, raised beds are an advantage as they cut down on regular maintenance. A raised bed system can look attractive and the soil can be tailored in each bed for particular crops.
Most of the raised beds constructed on our allotment are 4ft by 10ft which is an adequate size to grow most crops. I’ve also constructed beds that are 10ft by 10ft which provides some extra space for crops such as potatoes and squash. This system of raised beds will continue into the other half of the allotment still to be cultivated .
Conclusion
Waterlogging is a serious problem faced by many allotment holders across the country, especially during the winter months. It can be daunting to see your allotment looking like a pond but don’t give up. Waterlogging can be resolved if you put in the work and utilise the methods described above.
Further reading:
Alys Fowler’s excellent article on growing a wide diversity of fruit and vegetables as the best way to mitigate changeable weather, particularly by growing perennials. Available from the Guardian: Alys Fowler: how to cope with changeable weather.
The RHS: Waterlogging and flooding
The November issue of Grow your Own Magazine has advice for waterlogged veg beds.
Are you troubled with waterlogging on your allotment? I’d love to hear from you. Drop me a comment below or connect with me on Twitter, Instagram and Pinterest.
Sharpen your Spades 
I have the opposite problem. My soil is sandy and very free-draining, and my property is on top of a small hill. The result is that the soil often goes excessively dry, almost dusty. As you know, I use raised beds, and one of the reasons for this is that I can apply my irrigation efforts to only those areas that need it. After a very dry Autumn so far, I wonder what this Winter will bring?
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That is hugely different to what I experience! Summer must be quite busy for you then having to water the beds quite religiously I should imagine. Do you suffer with maintaining the fertiliser and feed in soils too? Does it drain everything out of the soil?
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Isn’t it something that the one thing – water – without which everything would die is also the one thing that most concerns gardeners (after whitefly, greenfly, blackfly and McFly).
Richard has too much of it (clay soil) whilst Mark has too little (sandy soil).
So some water management is needed.
Carrots.
Uh? Richard, work out how deep your carrots grow. Then plan your raised beds to be that much off the ground. You could also work with the lie of the land to dig a deeper trench down the middle of your paths and fill it with gravel, then replace soil on top. Create a soakway to send the water down to the plots lower than yours. And stay schtum!
Mark, it’s the opposite. Consider digging a trench or two. Get thee some pond liner or similar (damp proof membrane’s good) and make some barriers downstream to hold back the flood. How deep the trench is depends on how deep your topsoil is before you hit bedrock. But you know that, don’t you!
And, of course, in both cases, organic matter will help. More in Mark’s case than Richard’s, I guess.
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Some great advice. Must say my approach seems to have worked well. If it’s another soaking wet winter this year that will be the test!
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If I’m remembering the soil management section of the RHS course right, you can also flocculate clay soil by adding lime (I think gypsum was said to be the best form to use). Of course, that will have an effect on the pH of the soil, but it might be handy for any sections of the plot that are going to be dedicated to brassicas next season. And you can balance out some of the alkalinity by adding plenty of organic matter at the same time, which will naturally tend towards acidity as it humifies.
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Thanks Darren. I didn’t know that about lime. I believe clay tends to be an alkaline soil. Can’t get enough organic matter into this stuff. Must say the soil is pretty good since putting in the work over the last 10 months.
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Usually I wish we have a bit more rain. This year we are running at 50% of the long term average rainfall. Lots of mulch helps but the veg does need the sprayer periodically. Nevertheless a great blog.
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Thanks Steve. Yes, funny enough I thought the same as I wrote this. It’s been strangely dry this autumn even here in South Wales. I wouldn’t mind a relatively dry winter this year as I’d love the time to cultivate the rest of the allotment.
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I’ve had one dry winter and 3 sopping wet ones, so this year I’m putting in a land drain (10m of free pipe, all hail freecycle!). We have one on our main path, but my plot slopes the other way so it makes no difference to me.My beds aren’t raised much (15cm) but it does make a difference.
I have used lime, but not masses, and it’s not changed the soil much in 4 years. Green manure in winter and loads of organic matter in Spring IS slowly making a difference. If you are liming, don’t add manure for about 3 months because the two can react to make ammonia and then you lose your nitrogen…
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Hi Beryl. Thanks or this. It’s amazing how much difference raising the beds even a small amount makes. Since doing all of this to the plot it is much better. The winter will be a big test if it’s another wash out. My plot doesn’t seem to slope hence the way I have put drainage in. The other issue if I could have put a land drain in was not really having anywhere to run the pipe too. I’m enclosed by other plots so it’s awkward. Anyway think I will have it sorted this way. Fingers crossed 😊
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Very good point re: the ammonia, Beryl, which had completely slipped my mind. You can mitigate the risk by using less nutrient-rich o.m. like leaf mould, which will still help with the flocculation. But yeah, don’t mix your lime and horse muck.
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My plot flash floods, and some areas of it lie wet too. Raised beds are the solution for me. Keeps the topsoil above the water level, and the sides stop the soil being washed away. Needs extra watering in summer though. You can grow veg anywhere, it’s just what you’ve got to do to adapt to conditions!
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Hi Wendy. Absolutely! Likely the Welsh climate but I don’t really have to do much watering on the plot with the exception of new plants and if it ever is really dry (can’t remember when that last happened 😊) I used all three methods to improve my plot because I had to but raised beds will probably be enough to solve many people’s problems.
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How did you get by the last couple of winters?
My wife and I just took on a plot, and on clearing, we find it’s a bit of a valley. Apparently, the. Idle sank a few years ago, and since then several peo0le have come and gone…because of the water logging.
We weren’t told this by the allotment society, sadly, but by our neighbours.
It looks like I’m going to have to put in a tremendous amount of spadework to return It to the gentle slope it should be, and also to add some drainage.
I’m intrigued by your approach of filling trenches with woodchip…Was it just woodchip? How deep? Do the paths compact ok? How much have they rotted down, and how much have you had to top them up?
It must have been many cubic meters of chips?
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