Heavy clay drainage issues

[Amateur Devon]

Dear forum members,

 

I am reaching out to the community to seek advice on how to treat the soil in my garden to enable me to plan an ornamental tree and not be concerned about excessive watering.

 

For context, my house is located in a relatively new development in East Devon. The type of soil in the area is very clayey thus waterlogging is a very common issue in the community. We've been in the house three years now, and did some work to the garden a year after we moved in. The works consisted on enlarging the patio area, installation of artificial grass and installation of raised beds all around the perimeter of the garden. We have a rather energetic dog, which doesn't mix well with muddy lawns, hence the artificial grass, which is very practical for us.

 

We did however cut a circular opening in the middle of the garden to enable future planting of a Prunus Kanzan (a cherry tree variety). To do so, we excavated a knee deep hole and mixed in compost and grit with the native clay before planting the tree last September. The tree has been following its regular cycle of dropping its leaves, blossoming and growing new foliage and branches.

 

Unfortunately, a couple of weeks ago, maybe three, we started to notice its leaves drooping. We couldn't really pinpoint the issue, but we suspected it might have been something in the soil, potentially poor drainage after reading some articles and forums online. Our suspicions were confirmed upon excavating the hole; we've put the tree back into the original pot after rinsing the roots and placing some fresh soil (not sure it will survive, but would be keen to know people's opinion of what they'd do to increase the tree's chances of survival).

 

I have read online that a way we could break up the clay is by laying some gypsum into the hole. I'm thinking this would also be necessary beyond the hole, but the artificial grass is in the way, so not sure whether it would be as simple as applying it on the grass itself and rinse it with a hose so that the gypsum dissolves and percolates through the grass and underlying compacted sand and gravel until it eventually reaches the clay?

 

What do people think about this? We'd really like to plant a tree in this location without having to take out the grass.

 

Photo descriptions:

Photo 1: detail of hole

Photo 2: recently planted tree last September

Photo 3: new foliage and flower buds

Photo 4: detail of new leaves and flowers

Photo 5: drooping leaves a few days ago

Photo 6: drooping leaves today after taking tree out of ground

Photo 7: detail of free standing water in hole. I added the water some three hours ago to measure drainage rate. Water level hasn't moved at all in this time, which clearly shows waterlogging.

 

Many thanks for any help or advice you may be able to provide. I should add that my knowledge of gardening is extremely limited!

 

.. 

 

Edited May 12 by Amateur Devon
Change photo

[dumper]

You would be better getting goldfish

[dumper]

My solution would be to re excavate the hole trying not to smear the sides, use a fork and don’t stand in the hole.fork the bottom to full depth of the tines then add two cups of lime  mix in a 150 mm layer of gravel then backfill the hole with quality topsoil, not the. Compost / sand crap that most sell, then plant your tree on a raised mound, perhaps get smaller tree 

also would put drains under the artificial grass the tree pit is acting as a sump

 

Edited May 12 by dumper
Grammar

[Steven P]

so.... new build house sounds like the developers scraped off all the top soil down to the clay.

Big impervious patio area

Artificial grass - not sure how porus this is but it has a nice big drain hole in the middle for all the rain water to run off into,... which is where the tree is.

That's where you are at?

 

My view is that all the rain water isn't going very far and what drainage it can find it is filling up - the tree hole.

 

Looks like you need to add some sort of drainage to take the water away from the garden and not leave it in a hole in the middle - a trench part filled with gravel and then soil on top sloping away and to somewhere suitable to accept it. Are you able to peal back the grass around the perimeter to add drainage in there?

[dumper]

What I should have said

[difflock]

Regardless, I understood your dilemma, and can only suggest a "cam-o-flay" aka a shaped charge(of explosive) to blast a hole down through the impervious clay.

From vague RE memories of 40 years ago.

[Ollie_M]

following from difflock, on clarksons farm a company came out and used high pressure air to create cracks in the clay, they then filled the cracks with seaweed to hold them open - they did it in a puddle and you could see the bubbles coming up through the puddle showing where they aerated the clay. i would say worth looking into.
also agree that that hole is the only permeable bit of your garden and is therefore acting as a sump for all the run off, a vigorous grass would help with this as it would hold the water and use it rather than letting it runoff however you wanted artificial so it is what it is

[Amateur Devon]

2 hours ago, dumper said:

You would be better getting goldfish

This is plan B. Plan C consists of enlarging the hole and build a swimming pool.

[peds]

There isn't a single thing in the whole garden except that small tree to soak up the rain. 

 

I'd recommend a similar remedy to difflock's approach, but try and keep the blast above ground. Then start again. 

[Amateur Devon]

2 hours ago, Steven P said:

so.... new build house sounds like the developers scraped off all the top soil down to the clay.

Big impervious patio area

Artificial grass - not sure how porus this is but it has a nice big drain hole in the middle for all the rain water to run off into,... which is where the tree is.

That's where you are at?

 

My view is that all the rain water isn't going very far and what drainage it can find it is filling up - the tree hole.

 

Looks like you need to add some sort of drainage to take the water away from the garden and not leave it in a hole in the middle - a trench part filled with gravel and then soil on top sloping away and to somewhere suitable to accept it. Are you able to peal back the grass around the perimeter to add drainage in there?

I don't think peeling back the grass should be too much of a problem. I could possibly dig out a trench and fill it up with gravel around the perimeter of the hole and continue it downstream towards the back of the garden to intercept the flows that are filling up the hole.

 

Although this will help, I'd still be left with the actual hole itself which, even if I replace the material to fill it up with something more porous, it will still be lined by the native clay. I suppose that with frequent rain, this will end up filling up with water anyway?

 

I'm wondering whether the conclusion to this is that, without doing any major works, having a tree there is not compatible?

[Amateur Devon]

31 minutes ago, Ollie_M said:

following from difflock, on clarksons farm a company came out and used high pressure air to create cracks in the clay, they then filled the cracks with seaweed to hold them open - they did it in a puddle and you could see the bubbles coming up through the puddle showing where they aerated the clay. i would say worth looking into.
also agree that that hole is the only permeable bit of your garden and is therefore acting as a sump for all the run off, a vigorous grass would help with this as it would hold the water and use it rather than letting it runoff however you wanted artificial so it is what it is

Not seen that, but sounds expensive! 

 

Agree that natural grass would help, but the underlying soil will still be clay, so in my mind a few rainy days is all it would take to flood the hole anyway...