Planting hole COMPLETELY waterlogged :-/

jamesharcourt · October 2019

Help! Last night's biblical rainfall has created a situation where the deepest hole in the garden, with the free-est draining soil mix inside - has just filled with water. With a previously "fairly" happy Sango-Kaku inside :-// See the vid below, I had to take the Sango Kaku out (full rootball which was totally waterlogged / dripping). Ideally I want to put it back there and solve this drainage issue but not sure what to do. I tried using a mallet and a 6' stake to hammer 5' holes but it doesn't seem to drain away still. The hole was 3-4' deep when it was dug out (clay) and replaced with free-draining soil ... but it seems that at the bottom of that is a basin and the amount of rain last night has just filled it up and the drainage rate is so slow that 7 hours later, it hasn't gone anywhere. Any suggestions??

https://youtu.be/5gPyfzWx-AA

BobTheGardener · October 2019

That is a textbook example of creating a 'sump' which is inevitable when digging a hole in heavy clay and water from the general area will now always drain into the sump. The only real solution is to install a drainage system under the soil, assuming you have somewhere to drain the water to, such as a nearby ditch. If the local water table is high, you may be on a hiding to nothing though. It's going to take a huge amount of work, even for a small area. Deeply digging over the whole area (including lawn and borders) and adding as much organic matter and grit as possible (I'm talking 50l or more per square metre) may also help but you would probably still have to choose a tree species which can cope with waterlogging. Building a raised planter for you favoured tree is the only relatively easy way out of this one, I reckon.

Fairygirl · October 2019

I'd agree with @BobTheGardener too. If it was me, I'd go along the raised bed route for the Acer. It would be a pity to lose it.
My Dad had the same problem with drianage in the front garden. He built a sump, about 3 or 4 feet deep, filled it with gravel, which then became part of the pathway, and it worked very well. They had a peony just beside it after that

Lyn · October 2019

We’ve got sumps around our garden for drainage, rain water doesn’t go into septic tank.
As gravediggers we’ve seen plenty of holes filling to the top with water!

jamesharcourt · October 2019

If I dug another hole behind it (in an area lower on the overall garden slope), would the water drain into this instead?

What I’ve done for now is use a bucket to remove as much water as possible, then add 100L of my homegrown compost mixed with pine bark fines and plant the Acer tree in this with the base on the rootball level with the ground level (with the boggy soaked soil a few inches below this).

I did have a wisteria there for a whole season which didn’t suffer ... I think the rain of the last week or so has been more than I can remember in years ....

Borderline · October 2019

From what you describe and what I saw on Youtube, it's going to happen again because you have dug so deeply into the clay soil and created as others have said a sump. It's not ideal to dig so large an area for a tree that size. The best way is to dig wider instead of deeper so the roots adapt quicker to its surrounding soil.

Even in high rainfall at this time of year, water will flow around the heavy clay soil, but unlikely penetrate deep down to even a foot at this time of year. But because the soil has been worked on so deep down, there is a risk of the same thing happening again unless you back-fill clay soil mixed very lightly with a bit of compost.

Creating a raised bed there may be the best option, otherwise, you will need to back fill clay soil back into that area so there is less chance of water rolling into that loose soil.

Trees, even Acers can cope with some water-logging and heavier soils. It's always worrying to see scenes like that and think the worst. But even a few days sitting in water is unlikely to damage your tree at this time of year.

I think you could have planted your tree into the clay soil and not need to change the soil so drastically. When winter rain and autumn heavy rain comes, the water would collect, but not pool around like that. It's actually long-term rainy wet weather in the cold that normally causes more damage to some plants in the winter. But trees are more better equipped to deal with this. With no leaves and the growing shut down, they are less likely to suffer as much in the winter wet.

jamesharcourt · October 2019

Thanks @Borderline.

I should probably explain better… The reason for the original size of hole was that there had been a mature tree there that had become diseased and died and I was advised to replace the soil. The tree I now have in there is much smaller. I actually had a wisteria tree there for about a year before moving to a sunnier spot.

I have manually removed as much of the water as possible and backfilled this hole with my own homegrown compost and grit. At the moment it looks like this:

The sludge is a good few inches below the base of the rootball now.

Borderline · October 2019

That now explains for the huge size digging.

It's tough to call for this one. In this instance, I would get bags of top soil from the shop and pour it into that area to compact the area back down. Gardening can be very slow process at times. You would need a period for it to rest and slowly allow the soil to drop down as rain gets into the area. This can take a month or more. Then start digging the hole to plant your much smaller specimen.

But since it's all done, for now, it will be fine. Don't worry too much about adding grit for your tree. They will be fine without it. Grit is usually in containers but in the ground out in the open, water will move away from the root space. Acers are in more danger of getting dry and getting sun and wind scorch.

A mound will help the water slide off, but be mindful it may not last long and will need you keeping your eye on the levels possibly dropping over time. I think, if you have gone to the trouble of digging such a large area, it's best to replace the soil with a heavy loam based soil to help keep the soil around the area very similar to the surrounding soil. In the event of heavy rain, the water will spread more evenly rather than collect to an area of loose soil.

Hostafan1 · October 2019

This is precisely why my heart sinks when certain TV presenters bang on about putting grit etc in the bottom of planting holes " for drainage"

jamesharcourt · October 2019

Thanks again @Borderline

The compost I used to backfill the hole is my own made up from things originating from this garden including some clay ... I hot compost through the summer so produce quite a lot of it. It isn’t particularly light and airy or “loose” without adding perlite, I’ve found.

Either way I imagine when this all sinks down it will end up 20-30cm lower than it is not so I guess I’ll need to put down a load more.

Ultimately I think I need to dig another hole behind it to act as a sink but even then ... where will that water go?

Makes me think - where was all this rain last year when I needed it and stuff was being cooked 😬😬😬

Fairygirl · October 2019

I'm with @Hostafan1- I've never subscribed to the 'put gravel in the bottom of the planting hole' malarkey. Might be ok in drier areas, but asking for trouble here!

I wonder if the old tree has created the problem @jamesharcourt? By that, I mean that the route of the old trunk and roots has made it easier for water to travel to that area. Also, the old tree would have been sucking up any excess rainwater you were getting.

Planting hole COMPLETELY waterlogged :-/

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