Clay soil means hard work for growing vegetables (although those that survive quite often thrive). The main remedy, to dig in organic matter, such as manure or compost, can significantly improve the ground but it is unlikely to result in clod-free, non-compacting soil.
Raised beds are a potential solution. They can be filled with the soil type you want, they warm up faster (than clay – enabling earlier sowing) and they tend to be very fertile so crops can be planted closer together.
In an effort to better manage a clay garden, I have been researching how to install a raised bed, establish what can be grown in it and understand how to manage the bed to maximise its potential. This is a summary of what I found out and some links to sites that I found useful.
Options For Creating a Raised Bed
Assuming you have decided roughly where, the decision of “how to build” and “with what” is impacted by the following criteria:
- Cost – what’s the budget?
- Robustness – do you want to be able to rest or sit on the bed edges?
- Permanency – is it intended to be a long term feature in the garden
- Aesthetics – is the bed on display, does it need to fit in with an existing arrangement of beds, etc
- Who is going to build it – if its you, have you got the right tools for the job?
- Materials – Various materials can be used to construct a traditional shaped bed – these tend to range from bricks, to wood (often sleepers, scaffold planks or kits) to UPVC kits. But any container of a suitable size can be used to create a bed.
Obviously what material you choose will be determined by the above criteria, but installing a bed doesn’t have to be complicated or costly – a raised bed can be ordered from Amazon and constructed in a couple of hours, if that is what you want.
A couple of other things to bear in mind when choosing your material:
- Toxins – old sleepers and wood may have been treated with chemicals that could leach in to the soil
- Footings – if you are going for a construction that needs to last you may want to dig down in to the existing ground to create some form of footings.
- Size – How big? The advice was very clear on one point – you do not want to walk on the bed, so you have got to be able to reach at least half the width. For that reason the recommended width is approx 1 – 1.2m, assuming you have got access from both sides of the bed. The length is more flexible although it may be determined by your material (eg sleepers come in about 2m lengths, so a 1m or 2m length bed means no wastage) and less solid materials may require some support along the length.
When you have decided what you think you might like it can be useful to mark out the size on your ground so that you can see how big it is, how much room it will take up, whether you will have any odd bits of ground left over (and what you think you can do with them), etc. It is also worth thinking about the paths around the bed especially if you are constructing beds near to each other – not forgetting that you may want to be able to kneel down in between beds and/or get a wheelbarrow along the path.
- Height of the bed is also a factor that may affect your choice of material (ie in terms of how robust you feel the structure needs to be and how you plan to hold the construction together) but a minimum height of 15cm is suggested.
- Lining the bed – The need to line the bed with black plastic seemed to be more debateable – protection for a wooden frame was an obvious advantage and, if the bed has or is likely to get, other plant roots straying in to it then lining was suggested. The only other lining advice I found was about using mesh to stop small furry creatures moving in!
- Soil – It always takes a lot of soil to fill even the smallest container and, if like most back gardens there is restricted access, some one has got to transport all that soil to the bed!
With a raised bed you can of course vary the mix of soil/compost and, if you have dug down, you may want to use some of your own soil in the mix . But the advice is definitely to include to include organic matter to help retain the moisture. The mix we settled on was 1 part organic matter (in our case compost), 1 part sand to 2 parts soil, topped off with mulch.
Who Builds It
There are lots of on-line guides and videos to help you construct a raised bed. With a bit of planning and some preparation it looks possible to make your own from scratch. I have put together various kits in the past, which so far have all been easy and held together. This time we opted for sleepers so we had them delivered and the bed constructed as one job.
What you can grow
Apparently pretty much anything can be grown in a raised bed. I have grown strawberries and specialist veg but this time am planning to grow a few vegetables that haven’t done so well in the clay eg onions and carrots. The main issue with raised beds is watering – they drain faster so dry out more quickly.
In the Rest of the Vegetable Plot
If you aren’t converting the whole of your vegetable plot then the following are the most sucessful fruit and vegetables that we have grown in clay:
- Potatoes – Earlies and Main do well although our Earlies can be a little late.
- Beans (Runner / French / Broad) and Peas
- Brassicas, cabbages, brussels, kale
- Soft fruits – we have a range of currents, gooseberries, raspberries and loganberries
- Fruit trees – Apples, Pears, Plums and Cherry
Links
http://www.gardenersworld.com/how-to/projects/creative-projects/how-to-build-a-raised-bed/271.html
http://apps.rhs.org.uk/advicesearch/profile.aspx?PID=428
http://www.carryongardening.org.uk/files/documents/How%20to%20build%20raised%20beds%20final_Nov08.pdf
http://www.gardenorganic.org.uk/growyourown/Activities/A10.pdf
http://www.organicgardening.com/learn-and-grow/raised-bed-gardening?page=0,2
http://www.raisedbedgardener.com/growing-vegetables-raised-beds.htm
http://www.thompson-morgan.com/how-to-grow-plants-in-raised-beds
http://www.organicgardening.com/learn-and-grow/7-secrets-high-yield-vegetable-garden?page=0,0
http://www.gardeners.com/Soil-Calculator/7558,default,pg.html
http://eartheasy.com/raised-beds-soil-depth-requirements.html
Clay Soil
http://apps.rhs.org.uk/advicesearch/profile.aspx?PID=620