Need advice filling tall raised beds, TOP SOIL OR COMPOST?

dd.cole

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!

Pete.8

I had similar raised beds made a few years ago.
I filled them with about 80% topsoil and 20% rotted manure.
In hindsight I should have added grit too as the topsoil was very fine.
So I'd guess something like 60% topsoil 20% rotted manure and 20% horticultural grit.
Put the topsoil down first mixed with the grit then dig-in the manure to the top layer.
I got my topsoil from CPA Horticuture - very good quality too, but also very fine with no stones or grit of any sort - hence the need for additional grit.

Bags of compost (e.g. Levingtons) won't last long as it disintegrates, but you could add some if you like.

Good luck and Happy New Year

josusa47

It rather depends what you plan to grow.  If you are planting fruit trees, bushes, rhubarb or asparagus, which will stay put, do as Pete says.  But, if you are only growing annual crops, you could save a bit of money by filling the bottom half with rubble and/or discarded packaging material, that way you will use a lot less soil and compost.

dd.cole

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.

pansyface

Filling the beds with junk like bricks and stuff is just wasting depth and space. You might as well have built the beds that much lower or stuck them on trestles. Also cement is very alkaline. Not good for some plants.

Apple trees cannot be grown in such shallow and restricted spaces, no matter how dwarfing the rootstock.  See the RHS website for more information on apple cultivation. Here is a taster.







Also, a bed of only 27 cms depth is going to need constant attention to watering from late spring to early autumn. Maybe invest in a built-in drip system.

dd.cole

pansyface said:

Also, a bed of only 27 cms depth is going to need constant attention to watering from late spring to early autumn. Maybe invest in a built-in drip system.

Even if the bottom of the raised 27cm bed is open so the roots can go into the ground?

pansyface

Depends on the ground. If the ground is well supplied with water (soggy rather than sandy) then maybe you will get away with it. But I have to water anything in a tub. I have apple trees in 90cm deep plastic tubs (plastic being non absorbent and therefore “wet” as opposed to timber or terracotta which is “dry”) filled with top soil (the equivalent of your ground) that need watering every day in summer.

coccinella

Hello everyone and Happy New Gardening Year. I have had a tall (90 cm) raised bed built and the gardener used a German method (Hügelkultur) which is to fill the bed first with cuttings of thin/medium branches of any tree or shrubs then compact it down with a lot of stomping (two big fellas were jumping on it for a while) then fill it up with compost, and then more stomping.  I am totally new to this method and had my doubts especially the fear of those buried branches coming to the surface as babies.  But he has guaranteed that this will not happen. Fingers crossed for me? 

Microagent

I can share my own experience with my raised beds. They are two sleepers high, we filled them with garden clay soil mixed with garden compost and leaf mould. I was planning the have there sun loving plants like salvias, cannas, dahlias. The biggest problem turned out to be is drying out. Because it's raised it dries out in hot sun. The plants were struggling and never thrived. So, I enquired that to keep the moisture I must take all the soil out and line all the sides of the raised bed with plastic membrane. That's the plan now. 

Hostafan1

Microagent said:

I can share my own experience with my raised beds. They are two sleepers high, we filled them with garden clay soil mixed with garden compost and leaf mould. I was planning the have there sun loving plants like salvias, cannas, dahlias. The biggest problem turned out to be is drying out. Because it's raised it dries out in hot sun. The plants were struggling and never thrived. So, I enquired that to keep the moisture I must take all the soil out and line all the sides of the raised bed with plastic membrane. That's the plan now. 

Cannas  love sun, but they love LOTS of water too,dahlias love sun, plenty of water in summer and none in winter,  whereas salvias love sun , but not a lot of water. 
I'd change your plant choice and amend things  to whichever you choose, but I'd not grow those 3 plants together.

Microagent

Thank you Hostafan for your suggestion. Tropical hot bed was the theme for that area. And the drying out issue has to be sorted first. I know that my clay soil helps retaining moisture in the right conditions.