How to remove clay soil?

[Amylee]

Hi..

My Mum has very heavy clay soil that she had someone plant Japanese maple and some Ficus emeralds(not knowing anything about soil or plants she just asked for a nice garden)

Unfortunately they all died due to waterlog of how they were planted.

I tested the clay by digging a hole and filling it will water-1 week later it was still there.

Unfortunately she does not want to spend time amending it with clay breaker or building high garden beds..

I want to know if by getting a bob cat and removing about 20cm or more (unsure how deep it should go?) of the clay soil and then adding topsoil and some compost will be ok for when she wants to plant a new maple and ficus trees? Also will adding drainage pipes also help with drainage once some layers of clay is removed?

Atm the clay soil is smelly from where i had to remove the dying plants.

[MitchellMc]

Welcome to the Bunnings Workshop community @Amylee. It's sensational to have you join us, and many thanks for your question about planting in clay soils.

How deep is the clay layer? 

You would need to remove enough clay that there is sufficient soil under the plant's roots when they mature. Those plants have a reasonably extensive root system, so removing 20cm will not be anywhere near enough. Even as juvenile plants, if their root ball is 15cm deep, you'd need at least another 15cm of the soil underneath it for water to drain and not be sitting at the roots. Even to get a few years of growth without the plants being adversely affected by the clay layer, you'd need to dig down one metre.

It sounds like the ground might not be suitable for planting in. Have you considered having a truckload of soil bought in and building up a mounded bed? If you search landscape mound on Google, you'll see what I mean. This would be an easy way of creating a fantastic-looking feature that's suitable for planting in.

You could use excavation and drainage pipes to solve the issue, but if this is a solid clay layer close to the surface, you might be in for an uphill battle.

Mitchell

[twocutekelpies]

I would also look at googling clay soil friendly plants and checking out the neighbours' yards to see what grows well in that area. She could have a thriving native garden eg https://www.australianplantsonline.com.au/tubestockplants/plants-for-problem-places/clay-soils.html for ideas. Your local Bunnings may stock many of these varieties too. 

[Amylee]

 

Next door have beautiful ficus and the exact same level of land and they have successfully grown ficus plants..

How deep would these ficus roots grow?

Also would you know what these ficus are?

 

[MitchellMc]

It sounds like a great opportunity to pop over next door and ask them about their amazing looking Ficus @Amylee. I'm sure they would be thrilled to let you know any preparation steps they took before planting them and what variety of Ficus they are.

The plants look reasonably established, so you could expect their roots to penetrate around 60cm deep.

Let me mention @Adam_W, @Noelle, and @BradN to see if they have some thoughts on preparing clay soils for planting.

Mitchell

[Noelle]

Hi @Amylee 

Treating a heavy clay with clay breaker or gypsum might be a slow process but the end result is worth the time taken, if your mother wants a garden like the neighbour's! Mitchell is right in saying that you would need to go down at least a metre to remove the clay and then replace it with decent topsoil - that is, if you can find quality topsoil for the job and enough of it. This could prove the most expensive path to follow.

Raised garden beds - building the soil up on top of the clay layer to a depth of at least 600mm - may be a solution but it is absolutely crucial that you do not dig into the clay when planting. Diggi8ng holes into the clay will simply create sumps that will fill with water and drown the roots of your plants.  Your test holes have shown the clay is poor draining.

@twocutekelpies offers a good solution in suggesting planting shrubs etc that thrive in clay soils.  If soil treatments and building raised beds are not options, your mother may have to adapt her ideas to suit the soil profile.

[Adam_W]

Hi @Amylee, clay can be such a headache to deal with.
The best long-term solution is to use gypsum etc. but that is, realistically, something which may takes years.
The issue with removing some clay is that, assuming that there is clay soil underlying in a pan or layer, you are effectively digging a dish into the clay that will in-fact collect water. It just becomes a larger version of what happened with the planting holes.
Adding drainage in such a situation would likley be a very expensive exercise which would be a serious amount of work.
I have similar issues around here and yes, in some places I've built raised beds, but in others I have just created planting mounds. These don't have to be too large but they give the plants some roots space and then they will dive into the existing soil if they wish to.

You say the clay area is smelly... is it a smell like rotten eggs? If so there's a possibility that it may be an area of acid sulphate soil in which case I'd recommend you do not disturb that lower soil any more.

[Amylee]

Thank you for the reply.

The soil smells from where the plants that were waterlogged had been due to the root rot and is now contaminated.

I will have to be digging it up and removing it so it doesn't kill any new plants that will be planted.

I will most likely be getting drainage to prevent future issues and hopefully really good topsoil.

As for raised beds I will need to have a look but atm the soil is the main concern 

[Adam_W]

Hi again @Amylee okay, so if that soil that was added was high in organic matter & it has been sitting in a hole full of water then yes, it's likely getting smelly.
The biggest issue with drainage is making sure you can actually take the water away to somewhere. If that can be achieved and you're okay with the expense & level of work involved then not a drama.
And regarding a raised bed... this is all it needs to be. I needed to do this to plant a screening hedge as there was too much clay in the area.