Topsoil For Raised Beds | Turf Online Knowledge Base

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Topsoil For Raised Beds

Raised beds are undoubtedly one of the most convenient way of growing herbs, vegetables, flowers and fruit.  They’re accessible, neat and easily managed.

The best size for a raised bed

The idea of raised beds is that you never have to step on the soil.  That way there’s no compaction and in theory you won’t ever need to dig them over.

I’ve found that a raised bed that is just over 1 m wide by 1m long works best for me.  I’m 64cm tall (5ft 4 inches) and I can just reach the middle of the bed when I stand to one side.  That means I can reach everything without having to stand on the soil.

Height-wise – well it needs to be at least 15cm deep to accommodate enough soil to grow deep rooted veggies in.  But I prefer it to be a bit taller so I don’t have to stoop quite so much.  30cm is a good compromise and works well for me, my Mum is more comfortable with 60cm – she’s not ever so mobile and likes to perch on the edge while she works.

How much topsoil do you need to fill a raised bed?

It’s very easy to calculate the amount of soil you need for your raised bed.  Simply measure the length, width and height of the bed in metres and then multiply the three figures together.

So my raised beds are 1.2 metres long, 1.2 metres wide and 0.3 metres deep

Each one will therefore need

1.2 x 1.2 x 0.3 = 0.43 cubic metres of soil

Mum’s raised beds are 1 metre wide, 1 metre long and 0.6 metres deep

She needs

1 x 1 x 0.6 = 0.6 cubic metres of soil

One of those big builders’ bags of soil holds roughly 0.9 cubic metres of soil

What sort of topsoil is best for raised beds?

I like to be able to rotate the crops in my raised beds, so I need a good all-round topsoil.  One that is fine-textured enough to make into a seed bed but strong enough to support large plants like sweetcorn.

It needs to have plenty of organic matter so that it will retain water – but on the other hand, it must have enough drainage so that it won’t get sticky or waterlogged in wet weather.

I like it to be rich in nutrients, because that means I won’t need to work too hard to keep my plants fed.  I’m not a fan of big stones and I certainly don’t want to be buying in soil that contains the roots of pernicious weeds like nettles, docks or couch grass.

Personally I’m a fan of rich, dark soil like the organic loam.  It’s kind to plants and it’s kind to me.  When I’m moving the soil to fill my raised beds – a barrowful of this weighs considerably less than a barrowful of sandy loam, which is much better for my poor aching back.

I like this soil for potting up plants in the greenhouse and the polytunnel too.  It’s a bit too rich for raising seedlings but great for nurturing young plants.  Go easy on the nitrogen fertiliser though.  This soil is so rich in nutrients that you really don’t need to add many more.

The only drawback with this soil is that it does tend to oxidise so the beds need topping up every couple of years.  I find home-made compost is good for this.

Where to buy topsoil for raised beds

The big bags are a bit unwieldy but the company will unload them from the lorry for you and you won’t have a big heap of loose soil on your driveway.  All you need to do is shovel it from the bag into a wheelbarrow and then tip it into your raised beds.  It’s not perishable so there’s no rush.  You can take your time.  They’re competitively priced too – so what’s not to like?