Growing vegetables in raised beds is all the rage these days and for good reason - there are lots of benefits to growing this way, including healthier veg and an easier job caring for them! I've used a good few different techniques for converting areas of grass into raised beds and definitely have my favourites. Some are decidedly less hard work than others! Read on to find out what I do and to hear about techniques you can use, to make up new vegetable beds in your garden, for more lovely veggies!
I could go on about the merits of raised beds all day! Creating this type of vegetable garden is all about improving your soil structure, for better drainage, better moisture retention and better root penetration by your vegetable plants. When we work with raised beds, we're aiming to set up our space so that we never have to walk over our growing area, compacting the soil and crushing the tiny pore spaces that keep our soil 'open' and enable it to do its good work. Raised beds don't need to have solid sides - they can simply be mounded earth. So long as the soil in the beds is higher than the paths, you'll be getting all the benefit of growing this way. It's worth understanding a little bit more about that all important soil structure though before we go on to talk about techniques for building our beds. This will enable us to see how certain methods are more effective than others in creating a great growing space.
Good soil structure is traditionally made by digging over beds once a year to relieve the compaction caused by walking between rows of veg to tend and harvest them. However, much better soil structure is made by soil microbes. The tiniest ones - the bacteria and fungi - create a kind of glue-like substance that binds together tiny soil particles into little clumps, called soil aggregates or soil micro aggregates. These fit together in a haphazard way, leaving tiny pores and channels and creating a sponge-like soil structure that soaks up and holds on to any moisture falling onto the soil surface. Beneficial bacteria and fungi occur naturally in the soil, along with other microbe helpers, but populations will crash every time the soil is dug over. If soil is left alone and microbes are protected and encouraged, it will remain beautifully structured and will produce year after year of healthy vegetables.
So how do we get these beds set up? By far my favourite technique for setting up my beds is to use no-dig methods to mulch out grass and build my bed straight on top. This reduces the amount of turf stripping needed - a really back breaking job to do by hand - and it gives the microbial portion of your bed a head start by not digging them up, causing that inevitable population crash. The secret is to know that if grass is buried under six inches (15cm) of soil, compost, or plant material, such as straw or hay, it will simply die off, to be incorporated into the soil mass as organic matter. Another good thing to know is that you can speed up this process by laying down a layer of cardboard on top of the grass first (avoiding tape, plastic coated and colour printed cardboard).
So what does this mean practically for setting up your beds? Well we're using slightly different techniques, over different timescales, depending what type of mulch we use. Obviously opting for soil or compost for your mulching materials means you can grow veg into this space immediately, despite the grass hidden underneath it. I recommend using this technique if you're in a hurry to get growing!
Where I can, I like to source as much as I can for the beds onsite and so strip turf off the path areas and use the soil underneath to cover over the beds, topped off with home made compost. I dig out paths deeply to gain more soil for the beds and partially refill these sunken paths with woodchip, making sure to keep the ultimate path level a few inches lower than the final bed level. Using a cardboard mulch over the grass in the bed areas, with nicely overlapping pieces, actually means you can get away with a little less than 6 inches of topping, but it will be worth only trying to grow shallow rooting plants in the bed for its first year. Lettuce is ideal!
As you can see in the photo above, where using soil from onsite isn't possible - here our soil was extremely stoney - you need to import a mixture of top soil and compost to use to build up the beds and can lay wood chip straight over a cardboard mulch for the paths too. This is more expensive, but less labour intensive! Just be sure that the final levels leave paths sunken down from the beds. The photo above is how the garden at the top of the page started out. Top tip - we sourced large pieces of cardboard from a local bike shop.
The cardboard completely breaks down into the soil and from the second year, you can grow anything you like here without a problem. Microbes will quickly colonise the upper layer of soil from beneath, giving you that all important lovely soil structure.
Often though, I find it easier to source plant material as a grass-clearing mulch and this works extremely well, so long as you can plan ahead to get your beds built a good few months at least before you need them. For this method, I use straw, hay and even weeds and deadheadings and I build them up into layers of between 6 inches and a foot (15-30cm) over the whole area - future beds and paths alike.
As I said, you do need to plan ahead when using this technique, so that the grass is thoroughly killed off beneath the mulch, before you strip the covering back and grow into the soil beneath it. The minimum amount of time I mulch for is around 3 months and I will expect to need to do a little weeding after this time to fully clear the ground. This can be done without too much effort though, using a garden fork. If you can stand the wait, it is better to leave the mulch for a full year, after which you may still need a quick once over with a hand fork to remove any last stubborn weeds or small pieces of grass and then you're good to go.
Again, it's worth stripping some soil off the path areas to tip onto the beds, raising up their soil level, but with the grass already stripped, there is much less soil that will need to be moved around to make this work and so you can expect microbes to colonise your upper layer of soil more quickly than they did using the previous soil mulching method.
The other bonus of this technique is that you've effectively created a compost heap on top of your new vegetable bed area and compost is a fantastic way of generating loads of beneficial soil microbes. So you have not only kept soil disturbance to the minimum, protecting those tiny hoardes of helpers, but you've also massively boosted their populations, ready to help out once your veggies go in.
These techniques are great for new veg beds, but this year, I've used them to make myself a new bed for raspberries, as well as two new beds for currant bushes. I'm looking forward to getting a harvest from them in future years! If you feel inspired to open up more bed space this year, let us know all about it in the comments below!
If you'd like more detailed help setting up your vegetable garden for the year, my course 'Planning the Vegetable Garden' contains all the advice you need to get completely organised for a full year's vegetable growing. Find out more and book your place by following the link.
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