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Setting up and Looking After Raised Beds

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Mark Abbott-Compton guides us through setting up and preparing the ideal growing environment for your veg.

One of the commonest things I am asked is, “How do I increase the amount of vegetables harvested from the garden?” Well, over the years, gardens have become smaller and smaller, and many people no longer want to devote all their space to vegetables, but one of the best ways to increase your crops from a set space is by using raised beds. Using a raised bed (or ‘deep bed’, as they are sometimes called) can save you considerable space, time and effort – at least once they have been constructed – as you don’t have to walk on the soil, so don’t end up compacting the valuable growing medium. Experiments have also shown that you can grow plants with closer spacing, and, to clinch matters, the beds themselves are simply more productive.

I have experienced an increase in yields each time I have done a direct comparison between growing in the classic lines of a dug bed and growing in a raised bed, irrespective of whether that raised bed has been cultivated using a deep-bed method or a no-dig, layered ‘lasagne’ method. The only disadvantage is that you have to construct them in the first place, and if doing a classic deep bed, this will involve at least a dose of double digging. On the other hand, once you have prepared your bed, it will save you time because you’re not going to double-dig again for at least three years, and on a lot of soils probably only once every five years.

A further direct benefit of growing in raised beds is the fact that it is also much easier to control weeds – I suspect this is because the bed is normally no more than 1–1.5m wide, to keep it manageable, and because you are usually working in shorter runs it is easier to remain in control, as you can easily weed just a couple of rows so the task never becomes too tiresome.

Where I garden, I have a neutral pH level and wet soil, so raised beds have the advantage of both improving drainage and warming the soil quicker and earlier at the start of the growing season, but the controlled environment within a raised bed means you can exercise greater control over your growing medium. If your soil is sandy, the incorporation of lots of well-rotted compost will result in improved water retention in dry weather, and less stress on plants, and even heavy or compacted soils are easier to deal with.

One of the rules of growing in raised beds is that once you have prepared them you should not walk on the soil to avoid compaction, which is why I recommend a maximum width of 1–1.5m, as you will then be able to work from side paths, and 50–65cm is certainly an easy reach for most people. If you are working in long beds it is always best to put in paths, as, in my experience, if it is too far to walk round the bed, what inevitably happens is that you will step across them, compacting the soil and defeating all the good work you put in to create such a fantastic growing environment.

Raised beds can be created either using soil added to existing beds, or you can put retaining sides – usually wooden boards – around the edge. Putting a frame around the growing bed certainly makes the structure more robust, and prevents the soil from being depleted by rain and wind, while looking much neater, too. Sides usually look better in smaller urban gardens with more modern layouts. You can build them up using impressive railway sleepers or block kits that knock together, or you could just get some basic planks and work to your own design, with minimal effort.

 To produce a classic single raised bed I recommend you use measurements of 1m wide by 2m long, with 10cm-high sides. You could use 15cm-high sides, which are slightly more expensive, but will give you a deeper growing medium, which can be a benefit if you want to grow longer root crops such as carrots, long beetroots, Hamburg parsley, parsnips, salsify or scorzonera.

How to Make the Raised Bed

First, mark out your beds accurately. If possible, orientate them so that the long side of the bed gets the majority of sun, but it really won’t make a lot of difference to the amount of crops you will get from them. One thing I would suggest if you are going to grow in multiple beds is to try and make them all a consistent size – they will usually look better, but if you are going to make cloches to cover them, it will also allow you to transfer the cloches from bed to bed as needed.

Hooped cloches, or net covers in the case of brassicas, are immensely useful for keeping pigeons away, and for carrots you can use a very fine Enviromesh to keep off carrot root fly. Enviromesh or fleece will also increase the temperature slightly within the bed, so covering it with a layer of polythene will effectively turn a mini polytunnel into a cold frame.

Once you have marked out the bed, put some plastic or cardboard on the ground at one end, then, starting at the other end of the bed, remove the soil in pieces one spit deep and one spit wide. This topsoil is then taken to the other end of the bed and piled onto the plastic. What you are looking to create is a trench one spit deep – in most gardens this will expose the subsoil. The bottom of this trench is then broken up to the full depth of a fork. To do this, push the fork into the trench with the heel of your boot and work it backwards and forwards to loosen the soil – there is no need to actually turn it over.

Removing the soil in pieces.

Breaking up the subsoil.

Once you have worked across the trench, loosening this hard pan of subsoil, you then put a layer of well-rotted manure or garden compost across the trench. You will need a quarter to half a barrowful for each trench, if it is 1m wide. If you cannot get well-rotted manure, a decent alternative is mushroom compost. It is also worth noting that many local councils deliver green waste, which can also be used. If you have garden compost I would be tempted to keep it to one side for use in the top layer, and get the green waste delivered anyway. Once the bottom of the trench is full, repeat the process, turning the soil over into the previously dug trench, and inverting the spade so you expose the soil from the bottom – this means that any grasses or annual weeds are buried in the trench, and you should go all the way across the trench at this point. Garden compost should be incorporated into the top spit of soil.

Adding a layer of well-rotted manure.

Turning the soil over into the first trench.

Work down the bed until you come to the final trench, then incorporate the soil that came out of the very first trench. Remember, as you are working through the bed, that the annual weeds can be skimmed off and put in the bottom of the trench. Perennial weeds, however, are best removed and placed in a bucket, which is then filled with water. There they can remain until rotted down completely, when they can be added to the compost heap, and the water used as a liquid feed.

Filling the final trench with the soil from the first.

In the second year, there is no need to double-dig. Just single digging the top spit and incorporating a good amount of compost will give you a soil that is fantastic to work, and a delight to dig. Although you are only digging the first spit, it is still best to repeat the earlier action of removing the first trench, which makes it easier to go backwards and forwards.

Before sowing or planting in spring I recommend that you do a soil test to establish the pH of your soil. You can then decide whether you might need to add any specific trace elements. If you need to make your soil more alkaline you can add either lime or calcified seaweed.

If you are going to grow potatoes, they will prefer a slightly more acidic soil so don’t add lime. Raised beds may become acidic over time; this can be because farmyard manure is acidic. You need to remember that you cannot apply lime and farmyard manure at the same time, as they will react, causing a release of ammonia, which means valuable nitrogen is lost from the bed.

Experience has shown me that the best way to fertilise a raised bed is to use a good handful of fish, blood and bone scattered over the bed 2–3 weeks before you intend to sow or plant out your vegetables. If you live in a cold area, covering the bed with plastic will help to warm the soil, but will also cause the germination of some annual weeds, the seeds of which may have been exposed by your recent digging; however, it’s very easy to just hoe them off prior to sowing the bed.






About the Author:

Ruth Tott is the publisher of Home Farmer Magazine, and together with her husband, Paul Melnyczuk, Editor,is founder of the company. But her background is far removed having specialised in Costume History with a Post-Grad diploma in Museum Studies to boot. A far cry from looking after chickens, growing veg and making bread!

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