How Deep Should Raised Beds Be

How Deep Should Raised Beds Be

A question that is always asked here, especially from new prospective raised bed gardeners and that is, how deep should raised beds be ? The answers again are varied and will depend on a number of factors. A lot will depend on what we are growing, what quality is the soil, what is the prevailing climate like, is the soil arable and workable and what depth are the raised bed frames that we are working with. In essence the rule of thumb is, the deeper the better. In case that there is some confusion, a similar question that is asked in a roundabout way, and that is, what height should my raised beds be ?

The height or depth issues that we attempt to unravel today will be teased out and hopefully some clarity will emerge by the end of this post. Lets start at the beginning and work our way through the different scenarios and tackle each issue seperately. A good rule of thumb is that we leave the soil level at least 2-3″ below the top of the timber frames sides. This is because we may need to add some bark mulch at a later date and if we leave some room for this, we will ensure that the mulch don’t fall out over the sides. Birds may also scatter this mulch about, so we need to take this into consideration.


What are we growing;


This is  the most important of all the questions that is asked on a regular basis and politely I would suggest in most cases, its entirely up to the person themselves. They would work with what they have at their disposal, in terms of a raised bed frame and also work within their budget. So for beginners, and for the purpose of this exercise, we will work our way through the different and most popular vegetables and cover the soil depth requirements for each briefly. A standard raised bed frame measuring 4ft x 8ft and say that the sides are 8″ tall, then that is a great place to start with vegetables that will comfortably grow in this space and depth. Some of these would be, Cabbages, Lettuce, Strawberries, Onions, Leeks, and most of the common herbs like chives, spinach, celery, mint and so on. All or most herbs and salads would only need a few inches of soil to flourish and are really easy to start with. So in terms of work preperation, you can see very little is required for these varieties.


6-8 inch raised bed

Deeper rooted vegetables:


Moving on to the next category of deeper vegetable requirements and we will firstly look at how to have a better soil depth and how that is arrived at. If needs allow, a taller sided raised bed frame would accomadate these varieties and would require a little more prep work and planning. Again the soil is the common denominator and this is crucial for the successful growth of these veggies. The depth of soil we would be looking for would be in the region of  10 – 16″ at a minimum. The deep rooted vegs that we would be planting in this example are, Potatoes, Peas, Beans, Peppers, Carrots, Parsnips,Kale, Swedes and Squash and others in that vein. It’s easy to understand the soil requirements if we have been gardening prior to now and for the beginner or novice gardener, we will learn as we go forward. Experience will come with practice and for other reassuring measures, the growing instructions come with the veg. packaging. There are gardening experts at all the nurseries and garden centres, who will offer the best of advise at all times.


10 - 16 inch raised bed



Other deep rooting variety requirements;


There are a few species that require a greater depth of soil, such as, Tomatoes, Asparagus, Artichokes, Pumpkins, Watermelons and when we name these few, its easy see why these need that extra growing room, ie, when we see the fruits that these produce, its easy to understand their needs in this terms of garden room and space. How do we arrive at depths to accomadate these few vegetables that require a greater depth that the others ? Answer , double digging or really high sided raised beds. What is double digging, I hear you ask ! This is where we dig the soil within the bed frame area before we actually locate and assemble the raised bed. We would dig the soil to a depth of 12-16″ and then add some topsoil when the bed is in place and this would give us the deep soil measurements that we would need for these special varieties. A little more preparation than normal and a little extra hard work in the beginning, but the pay-off and rewards come later.


14 - 20 inch raised bed


Basic soil preparation;


The first layer of soil, say to a depth of 6″ is where most of the vegetables get their nutrients and growing requirements, so this is the most critical part of a raised bed or garden. Having this area well cultivated and fertilized, will pay us back by the bucket load. Ensuring that the soil is well tilled, aerated and also that it has good drainage will return high quality and good quantities of harvest. The beauty of raised beds is that we can improve the texture and quality of the soil at all times. Every year before planting, its a case of adding some good quality compost, farmyard manure or well rotted leaves or hedge trimmings. Just fork in and mix with the existing soil and we are good to go. Better still, if we could add this mixture just after harvesting and leave over the winter months to break down and integrate with the existing soil, that would be ideal.

If by chance that we would like to plant some of the deep rooted and short rooted vegetables in the same bed, a good tip is to plant the tall growing veggies towards the centre of the bed and the shorter ones nearer the sides or outside. This will ensure that the tall plants will not block out the sun or smother the smaller varieties.

I hope that this post will answer some of your questions and queries and if not, please use the comments box down under and we will reply to all your issues in due course.

Happy gardening to all who try and succeed,

Cheers     Phil Browne.


” There can be no other occupation

like gardening in which,

if you were to creep up

behind someone at their work,

you would find them smiling “.


~Mirabel Osler


8 thoughts on “How Deep Should Raised Beds Be

  1. You have built a good website. Easy to read. Nice to look at.
    I like the way you explain “double digging.” Didn’t know that is what it is called. Good point on adding sand to clay soils too.
    You sound like you know what you are talking about – and you do.
    So much information on raised beds. You’ve got a one stop website here.
    Beautiful quote about walking up to a smiling gardener too.
    Very professional. Very good website. I have bookmarked it.

    1. Hi there Suzanne,

      Many thanks for stopping by and offering great feedback. I am glad that you found this website and also that you found the information useful and informative. I am grateful that you liked the post and that you have saved it for later.

      Thanks again for stopping by,

      Best wishes,

      Cheers          Phil Browne

  2. Hi Phil,

    Great article! I have learned so much from your site and yet you keep posting great articles. Thank you!

    I have often wondered about planting root veggies in raised beds. I tried it once, but did not commit the proper planning and time to it, so I was never sure what I did wrong. Your guide on this helps a ton! I will be trying the double digging method in the near future.

    Thanks again,


    1. Hi there Jaimeo,

      Many thanks for reading this post and offering great feedback comments.

      I hope this idea will work out for your deep rooted veggies and there is no reason why it won’t. By double digging, we gain approx an extra foot of soil in depth, so it does’nt really matter what height the sides of the raised beds are, we can compensate by rolling up the sleeves, get the spade and start digging. It will give a greater return on the vegetables also, as this exercise makes growth much easier for the veggies. They like the arable, tilled, cultivated soil and our hard work will pay us back handsomely in the end.

      Thanks again for stopping by and happy gardening

      Cheers    Phil Browne

  3. Good stuff sir. I have a raised bed in the back yard and it out performs my “regular” garden each year. I haven’t done enough soil work on the “regular” garden. I followed along with a square foot gardening book when I did mine.

    I had an idea while reading your post maybe and I’m sure there are 100s of pins and posts with this same thing, but it just hit me so here goes……I’m going to put a smaller square like you said in the center and fill that with dirt. A second tier so to speak, b/c I never grow the deeper rooted stuff in the square foot garden even though it produces better. So thanks for the idea.

    1. Hi there Capt,

      Many thanks for stopping by and offering great feedback on this post. I agree with you that raised beds will outperform the open ground gardening all the time. In terms of quality and earlier produce, the raised bed system will work all the time.

      I like your idea and I think it could be a runner. Its a great idea and I guess that is the versatility with raised beds, you never know how good they are until we try them.

      Best wishes on your new plan and happy gardening,

      Cheers     Phil Browne

  4. Awesome article! I learned a lot today thanks to you. I know a little about indoor gardening but my outdoor game could use some improvement. Could you recommend some indoor potting mix or soil for marijuana? I am looking forward to your new articles and I will be talking to you in the future. Thank you!

    1. Hi there Karl,

      Many thanks for stopping by and reading this post, its greatly appreciated. I am glad that you found the article informative and interesting. Unfortunately, I have no experience in these types of plants that you have just asked about. I would suggest that any ordinary indoor potting compost would be adequate for this purpose, it might be an idea to ask at your local garden centre for advise, when purchasing this compost.

      Thanks again for stopping by

      Happy gardening

      Cheers     Phil Browne

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