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Need advice filling tall raised beds, TOPSOIL or COMPOST?

Hi all,

In the garden, I have large raised beds, 5 meters in total length and all with a height of 57cm (they are tall raised beds for an elderly member of the family)
They will be used to grow vegetables and fruit.

I am looking to buy something to fill these beds now I know this is going to take a lot of material needed to fill and that's fine but what my problem seems to be is what to fill these tall raised beds with?

When looking at multiple retailers they all seem to offer, topsoil, multiple types of compost, etc.

Do I fill the beds with a mix of topsoil and compost or just compost? I’m lost with what the difference between the two is as I’ve read that some beds are filled with only compost?
Also if a blend, how exactly would this be done? First topsoil then compost on top?
Looking for some advice on how you all would go about filling these massive tall raised beds. I’m lost with all this topsoil and compost talk.

Thanks in advance!


  • pansyfacepansyface PEAK DISTRICT DerbyshirePosts: 18,625
    edited January 2020
    Quite a project there.

    Given that most vegetable plants’ roots don’t go down that far, unless you are talking about potatoes, and most small fruit the same, strawberries and so on, I would say use top soil for at least the lower half.

    Firstly, it’s less likely to compact and need topping up. Secondly it’s cheaper. Thirdly, it will hold moisture for longer and not need so much watering.

    But top soil is heavy, so unless granny is a weightlifter compost will be easier to dig into, dig plants out of and generally look after so would be better for the top, working, layer.  

    For long term plants, John Innes Number 3 compost is the best. It doesn’t contain a lot of nutrients and is designed for long term steady growth. John Innes Number 2 is for short term plantings and contains more nutrients and is designed to give short term plants a quick boost to make them flower/fruit.

    Make sure that the walls of your planters are well water proofed before you start. If they begin to rot after a few years you will have an awful job restoring them.
    Apophthegm -  a big word for a small thought.
  • purplerallimpurplerallim LincolnshirePosts: 3,984
    I have the same sized beds, built just last year. I put a layer of straw in the bottom to aid drainage and a mix 2 to 1 of top soil and compost. From now on will be adding compost to top up the beds. Only use manure if you are growing potatoes,  not if you are planning root crops which need a loose texture of soil too. Hope you have reinforced the beds well and lined them, as they will be taking alot of weight. Hope this helps.
  • Hi all,

    Thank you so much for the input so far! The raised beds will be used to grow a wide range of veg and fruit such as (cucumbers, peppers, carrots, artichokes, tomatoes, various berries) 

    There is a shorter raised bed in the garden that is only 27cm tall that will have apple trees planted in.

    As there won’t be really any deep rooting plants other than carrots (and they really don’t need 57cm) I’m interested in putting cement air blocks that I have in the shed to bulk up the space at the bottom of the tall raised beds (not the shorter tree bed) But I have maybe a silly concern: is that safe to do? This may seem silly to ask but my thought is that it’s cement at the end of the day...will it leak any nasties?

    Also I’ve seen some replies talk about reinforcements in the raised beds: the majority of the beds are only 80cm wide so felt like these didn’t need the reinforcements in the centre of the beds. There are two beds that are 1.2 meters wide and these have reinforcements in the centre of the beds. The reinforcements are 10cm x 10cm solid wood posts, which are the same as what is used in all the corners, so it’s pretty heavy duty!

    Also I will line all the beds to try and prolong the life as long as possible.
  • purplerallimpurplerallim LincolnshirePosts: 3,984
    For things like carrots and parsnips you will still need 15 to 30cm of depth (depending on the variety),  so the blocks might get in the way. You need to leave about 10cm of space above the soil level so you can net the young growth to protect from pigeons, or build above the bed a frame for this. The first is easier. I even netted the potatoes this year to keep them off the young growth.🙂
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