Heavy dense clay

[SWOTHEAD]

I terraced a section of my garden which involved digging out heavy clay from a sloping bank. The result is a flat, raised area about 50M2, where i would like to sow grass seed and dig out the ground for 5 pixie size fruit trees.
Problem: water will not drain and lies in puddles. i considered laying a French drain, but the clay is so dense water will not percolate into the perforated pipe. When I ram a steel bar into the clay about 24 inches, i reach a base of rubble and the water drains, but only where the hole has been driven.
When the clay dries out it sets like concrete.
I can't see that digging a sump/soak away would work, for the same reason.

Amending the clay by digging in organic material/sand etc would be an enormous job and might not work.

Question: would laying say 3 inches of 50mm stone chipping and then cover with say 3 inches of good soil do the trick? Would the water drain away if i create a slight slope, or will it just accumulate and as the water table rises kill the grass and trees (eventually)?

Of course i could just gravel the whole thing, but that is not what we would like

Any suggestions?
Thanks!

 

[Marck]

Greetings, welcome to the Forums.

I found your other thread without the photo first. I'll post my reply there below. After seeing the photo, I will add that the situation is not hopeless. amending and mounding could turn such soil into a fine garden, at least for clay-tolerant species.

Of course, you want a lawn, so do amend generously before planting (yes, it will work) and then plant a grass species that is adapted to seasonally wet clay. Turf cultivars of Tall Fescue (Festuca arundinacea cvs.) might be a good option. Some say it makes a coarse lawn, but really it can look very good. It's a lawn, not a putting green.

If it is true that across the entire terrace, there is a 'base of rubble' that drains, you could do something with that.
Perhaps, dig a number of two-foot deep holes. one or two feet wide and fill them with a mix of gravel and compost.
Perhaps ten holes or so, depend how the 50 square meters are arranged.

Always consider plant selection. Plant species (grass or otherwise) that prefer heavy, seasonally wet soils.

 

[Marck]

Another reply originally for the other, more active thread. I'll add it here too, as it seem to still make sense out of context.

The description of the clay in the OP is not that different form the soil (clay is soil) found in the grasslands of California, as well as being the base soil of my garden. Unamended, it is heavy muck when it rains and concrete-like adobe when it dries. All the same, with water, the grass and many other plants grows lushly.

By all means increase the organic matter by amending with compost, but no need to wait a year. Seed or sod can be laid down immediately after. Plant selection is key.

 

[SWOTHEAD]

Greetings, welcome to the Forums.

I found your other thread without the photo first. I'll post my reply there below. After seeing the photo, I will add that the situation is not hopeless. amending and mounding could turn such soil into a fine garden, at least for clay-tolerant species.

Of course, you want a lawn, so do amend generously before planting (yes, it will work) and then plant a grass species that is adapted to seasonally wet clay. Turf cultivars of Tall Fescue (Festuca arundinacea cvs.) might be a good option. Some say it makes a coarse lawn, but really it can look very good. It's a lawn, not a putting green.

If it is true that across the entire terrace, there is a 'base of rubble' that drains, you could do something with that.
Perhaps, dig a number of two-foot deep holes. one or two feet wide and fill them with a mix of gravel and compost.
Perhaps ten holes or so, depend how the 50 square meters are arranged.

Always consider plant selection. Plant species (grass or otherwise) that prefer heavy, seasonally wet soils.

Very helpful Marck. There is hope! i'll give it a go. Thanks!

 

[SWOTHEAD]

Another reply originally for the other, more active thread. I'll add it here too, as it seem to still make sense out of context.

The description of the clay in the OP is not that different form the soil (clay is soil) found in the grasslands of California, as well as being the base soil of my garden. Unamended, it is heavy muck when it rains and concrete-like adobe when it dries. All the same, with water, the grass and many other plants grows lushly.

By all means increase the organic matter by amending with compost, but no need to wait a year. Seed or sod can be laid down immediately after. Plant selection is key.

 

[SWOTHEAD]

Thanks for the suggestions. i have now done as follows: perforated holes about 18 -24 inches deep with my "wrecking bar" (done while the clay was moist!), thin layer of gravel, layer of building sand (an inch or so) and finished with 1-2 inches good topsoil (i ordered a dumpy bag of 850kg, which just about did it. Sowed the grass seed two weeks ago and now shooting up. For plants (fruit tree and fruit bushes) i dug out 24 inch holes about 18inches accross and filled with good stuff. They seem to be thriving too. The grass seed is Johnson's Tuff Grass.

 

[lifegardener]

Thanks for the suggestions. i have now done as follows: perforated holes about 18 -24 inches deep with my "wrecking bar" (done while the clay was moist!), thin layer of gravel, layer of building sand (an inch or so) and finished with 1-2 inches good topsoil (i ordered a dumpy bag of 850kg, which just about did it. Sowed the grass seed two weeks ago and now shooting up. For plants (fruit tree and fruit bushes) i dug out 24 inch holes about 18inches accross and filled with good stuff. They seem to be thriving too. The grass seed is Johnson's Tuff Grass.

Love what you have done - absolutely beautiful.
Your trees will gradually help moderate the temperature below and around them - improving the conditions for many things to grow.