Clay soil under planters

jamiebrand19956AP2cmjK · April 2022

Hello all, I've recently built myself some raised beds out of old pallets planning to use the square foot gardening method as a rough guide for my planting in the bed & I've now noticed the only realistic place I can put them is on top of this patch which is thick wet clay soil that doesn't drain the best.
I dug it all out and raked it level for the beds to go on top & I poured over a can of water and it did drain eventually maybe upto 5 mins for 1 6L can of water. Doesn't seem Ideal.

My issue is. If I put my raised beds on top and fill them up with (still to decide my method of filling, open to suggestions) a growing medium and then start planting I don't want the ground under my beds to become waterlogged if it will at all? The beds are approximately 450mm-500mm high.

I'm thinking either it will be fine and the time my beds drain through and absorb what I put in it would give the clay plenty of time to drain also... Or it's gonna be a total pain in the butt.

Any of you came across this?
F.y.i. the pictures isn't the final place. I don't have a picture of that top hand (thought I did)

jamiebrand19956AP2cmjK · April 2022

jamiebrand19956AP2cmjK · April 2022

Fairygirl · April 2022

I wouldn't worry at all, especially with beds that height.
You should see what's under my raised beds

JennyJ · April 2022

I think they'll be fine. Have you tried pouring water into the raised beds in their final position (before filling) to check that it drains through? You might need drainage holes in the base lining if it's plastic (can't really tell from the pictures, maybe it's permeable membrane).

punkdoc · April 2022

You won't have a problem.

Nollie · April 2022

They look great. Yes, drainage holes in the membrane below if it’s impermeable fabric. You could always drill further holes in the bottom vertical plank if you find you need to.

You will need a large quantity of material to fill them and my only concern is that the pallet construction would not be strong enough to resist the outward pressure of the significant weight of all that soil/compost, especially when wet. To prevent the sides bowing out, I think I would screw in some sturdy 2x2” posts midway along each side. If you put them on the outside of the boxes you could knock them into the ground a little when in their final positions for extra strength, then screw them to the boxes.

What you fill them with depends on what you plan to grow it them, but usually it’s a good idea to have a mix of topsoil, compost and maybe manure. Compost on it’s own doesn’t have enough nutrient ooomph for very long and tends to dry out quickly. If the plants you are growing aren’t very deep-rooted you could always fill the bottom with building rubble, gravel etc., which also helps with drainage.

Fairygirl · April 2022

I would agree with @Nollie - the timber is very flimsy for the size of bed, especially if the growing medium is hefty.
They'd definitely benefit from some sturdy posts added.
Mine are all built with heavy duty fencing timber, attached to 3 inch posts concreted into the ground.

jamiebrand19956AP2cmjK · April 2022

It is a roll weed control fabric I've stapled to the bottoms. I did pour some water in and it just beaded. I thought it would've drained when I put it on initially. Going to puncture some holes in the bottom of it. I just used what I had. I'm only starting out on my gardening journey so I've went a bit mad with excitement and planted lots of stuff and then had that moment of "oh, where am I gonna put these when they mature" 😂.

Bracing is a good shout for the centres.

The corners have 50mm ring shank nails into 2x2 and a 50mm corner trim of metal hard edge screwed into the 2x2. Initially I thought that would be enough. I see the flaw in the middle between those corners now you say that @Nollie thank you.
I bet you can grow some amazing stuff over in Spain. Beautiful climate. I'm flying over to Barcelona on the 10th of may to catch the Barça Vs Celta Vigo game I can't wait. I've been a Barca fan for the last 15 years. Never miss a game on TV. (From Scotland)

I just used what I had to hand I had pallets left over that were gonna get skipped at a job I'm on and decided to repurpose them. Totally built for free except the wood stainer.
@Fairygirl do you happen to have a picture of yours? Or anyone else who might want to pitch in. I'm interested to see people's set ups

Thanks for the reply @punkdoc @JennyJ I'll brace it up a bit

hatty123 · April 2022

I've got raised beds on clay soil, mine are only about 20cm high, width of a scaffold board. I didn't use any kind of fabric at the bottom and haven't had a problem with weeds coming up (other than a very tenacious thistle I pulled 3 times before it gave up!). So I suggest taking the weed fabric out completely, the depth of soil/compost you have will be sufficient to suppress weeds and then you don't have to worry about the fabric hindering drainage.
Previous residents of my house used weed membrane everywhere, its started to degrade and put ribbons of plastic in the soil that I'll still be pulling out in years to come 😐
Like others have said, nothing to worry about with clay soil underneath. My veg does really well, even plants that require good drainage and not recommended on clay, the raised beds help prevent waterlogging.

jamiebrand19956AP2cmjK · April 2022

@hatty123 Okay, I'll take that on board. Thank you for your input. That's not ideal! The ribbons of plastic I mean. The fabric I've used is like a breather membrane. Its not plastic like the woven canvas type plastic you see. Its similar to breather membranes we use on roofs. Like you say though could probably do without it. As it doesn't allow the water to pass through so rather than poke holes I could just remove it.

What have you successfully grown in your beds? In this great British weather we have 😅.

Clay soil under planters

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