Building a wall around a tree

[Tierney]

Hi,

I've got a Mimosa tree in the garden that I want to build a small wall around. The problem is that a number of the roots are running at ground level (slightly above in some instances) and I want to know what will happen if I cut them to lay the foundations? The tree trunk is about 8" (200mm) and there are about four roots that I want to cut, the biggest is only 1" (25mm) in diameter.

All advice gratefully received.

Regards,

DT

 

[Mike.S]

I'm no expert but from from experience of digging up the roots of similar sized trees and a quick scan of my RHS book on trees/shrubs, I'd say:

1) Executive summary
Do it!

2) more thoughtful
From the picture you'll be cutting 2' plus away from trunk so stability shouldn't be impacted (given only 4 roots and max size of 1" roots). Losing roots this time of year may 'stress' the tree so some TLC afterwards (especially water) is desirable. Try to preserve the thinner, fibrous roots (often descend straight down from near surface roots) as much as possible - these are more efficient at water/nutrient gathering than the thick roots.

HTH.

 

[paulm]

I would just build with loose stones, like a dry wall, given that it is going to be a small area and low in height. No need for foundations for that situation, just use large enough stones so that they have sufficient mass to stay in place when/if the soil is topped up inside the walled area.

Wouldn't be hopeful of successfully cutting a number of roots that close to the tree, at this time of year in particular, and there may well be more roots you can't see yet once you start digging.

Having said that, trees do get moved/transplanted with that kind of sized root ball, not sure of failure rate though......

Cheers, Paul

 

[Jonzjob]

From our experience once you have a mimosa you can't get rid of it unless you freeze it to death! Our three died after almost 2 weeks of solid sub zero a couple of months back. All of our neighbours lost theirs too One neighbour, 22. Another has had to completelt change her garden layout she had so many. And they were quite mature too!

Cutting a few roots won't effect it, but as has been said a small dry stone wall would do the trick and you won't have to cut anything..

 

[Harbo]

The rule of thumb for Highway Construction schemes was to avoid any works or disturbance within the trees canopy.
One idea that comes to mind is create some supports (block work/bricks/metapost??) - carefully placed - bridge these with some narrow RC Slabs at just above ground level, then build on top?

Rod

 

[Tierney]

Thanks, I do tend to over-build on the basis that I don't want to do anything twice; hence the foundations. I think I'll have another look and try and build around most of the roots and maybe only cut back a couple.

As always, thanks for the advice.

DT

 

[CHJ]

Have you thought about using so called Railway Sleeper timbers to build what I assume is a shallow retaining wall for a small flower bed or bark mulch retention, no foundations needed, resistent to or accommodating of heave.

 

[Phil Pascoe]

You could get hold of some reinforcing mesh and/or rebar and create a shallow "raft" foundation - it would be unlikely to crack with that sort of weight on it.

 

[andersonec]

I would go the sleeper route too, lay them brick pattern where they meet at the corners and when they are in place, drill down in the corners and hammer in some copper pipe or something which won't rust and they will not move.
The problem is not so much cutting smaller roots, at this time of the year they will soon regenerate, what could cause more damage to the tree is the concrete you will be pouring into those trenches, tree roots and concrete do not mix, almost certain death unless you put in something in to separate them eg some builders plastic.

If you do cut them, make sure it is a clean cut (ragged cuts rot) and the cut face is pointing down, this is all to do with how the new roots grow from underneath the bark.

As mentioned previously, do not let those exposed roots dry out.

Andy

 

[Tierney]

Thanks, I think I'll go the sleeper route. I was thinking of using some brackets on the inside of the frame (i.e. wall) to hold the pieces together. I will now hopefully cut the roots properly and not kill the tree.

Thanks,

DT

 

[paulm]

Why would you cut the roots at all if now going the sleeper route, perhaps I missed something ?

Cheers, Paul

 

[Tierney]

Hi, I am turfing around the sleepers which will mean that a couple of the roots that are running along the surface need to go.

 

[Jonzjob]

I had a look at the base of our 'dead' mimosas and there are new shoots growing!!!!!

I doubt very much that you will kill your tree even if you tried to very hard!

 

[Lons]

I wouldn't worry about it Tierney.

It will take some killing if all you're doing is cutting a few 25mm thick roots near the surface.

I bet if you cut a 300mm deep channel all around the tree you still wouldn't be able to rock it due to the tap root and masses of other deeper roots.

I've done it a number of times, though never with a mimosa, (wouldn't recognise one if it hit me in the face). Never lost a tree yet.

Bob

 

[mickthetree]

The rule of thumb for Highway Construction schemes was to avoid any works or disturbance within the trees canopy.
Rod

Ah! that'll be why they pollarded all of the trees in our road, then dug down right next to them.

All makes sense now ;-)

 

[Tierney]

Cheers, on the basis that nearly every one of the other ten trees in the garden are rotten, diseased or dying this tree must be made of sterner stuff.

The Mimosa is quite a nice tree, lovely yellow flowers in summer, which is probably where the cocktail got it's name from, and let's face it an alcoholic drink that you can drink in polite company before midday deserves some respect, even it is a bit un-manly.

DT

 

[andersonec]

I wouldn't worry about it Tierney.

It will take some killing if all you're doing is cutting a few 25mm thick roots near the surface.

I bet if you cut a 300mm deep channel all around the tree you still wouldn't be able to rock it due to the tap root and masses of other deeper roots.

I've done it a number of times, though never with a mimosa, (wouldn't recognise one if it hit me in the face). Never lost a tree yet.

Bob

Bob,

There's a safe way to dig round trees and seeing if it rocks isn't a safe way, those larger roots are there for two reasons, one for stability (which you mentioned) and the second is the transportation of nutrients and moisture to the tree from the hundreds of fibrous roots that are attached to that root, those hundreds of fibrous roots are in turn fed by millions of root hairs which actually do the collection of moisture etc from the soil so when you cut one 25mm root you are doing more damage than you think, that 25mm root is not the one which is collecting the moisture/nutrients.

The root hairs which do the actual collection of nutrients/moisture are very fragile, there are some 400 per square mm, and if these are all killed by exposure to the air and being allowed to dry out it will do your tree no good at all.
If you need to cut roots then plan to do it when the tree is dormant, preferably when it is just waking up round mid march, if this is not possible then try to protect any exposed roots as much as possible, cover with hessian and douse with water every day.

Most trees will tolerate the removal of a few of their roots but there is a limit, especially when the thing is fully leafed out and in full growing mode, and the older a tree gets the less it will tolerate the removal of roots, especially those underneath the canopy.

A fully grown Oak will use circa 400 gallons of water a day ..............

Andy

 

[Lons]

Bob,
There's a safe way to dig round trees and seeing if it rocks isn't a safe way, those larger roots are there for two reasons, one for stability (which you mentioned) and the second is the transportation of nutrients and moisture to the tree from the hundreds of fibrous roots that are attached to that root, those hundreds of fibrous roots are in turn fed by millions of root hairs which actually do the collection of moisture etc from the soil so when you cut one 25mm root you are doing more damage than you think, that 25mm root is not the one which is collecting the moisture/nutrients.

The root hairs which do the actual collection of nutrients/moisture are very fragile, there are some 400 per square mm, and if these are all killed by exposure to the air and being allowed to dry out it will do your tree no good at all.
If you need to cut roots then plan to do it when the tree is dormant, preferably when it is just waking up round mid march, if this is not possible then try to protect any exposed roots as much as possible, cover with hessian and douse with water every day.

Most trees will tolerate the removal of a few of their roots but there is a limit, especially when the thing is fully leafed out and in full growing mode, and the older a tree gets the less it will tolerate the removal of roots, especially those underneath the canopy.

A fully grown Oak will use circa 400 gallons of water a day ..............Andy

Hi Andy

Yes I know all that and of course you're right but I wasn't suggesting that the OP actually cut around and rock the tree My point (badly made) was that the roots at the surface are only a small % of the total root system (which is why it wouldn't rock).
The tap root and deeper roots are perfectly capable of supporting the tree and collecting nutrients and water and will actively seek out a moisture supply, which is one of the reasons they damage drains. I've repaired drains packed full of roots doing just that.

It's also one of the reasons why building inspectors will insist on very deep found excavation if anywhere near trees. Many extensions are built under the canopy without killing the tree!

Have to use commonsense but as I've said, I haven't lost a tree yet and I've dug around plenty, I also have 3 mature bramley apples which have been transplanted 3 times in 20 years and bear heavy fruit crops as well as a 10 year old oak twice and it's growing like hell!. It's also why bonzai root pruning is successful with almost any tree with care.
I'm not a tree expert btw, just had and have a lot of experience and love the things. I do a lot of ground works for other people which conflicts with roots. Had to take out 7 trees on my own land a few months ago which I didn't much enjoy though left one very large poplar with a 400mm trunk at 2.5 mtrs height to see if it will pollard and there's sign of life.
Amazing things are trees :lol:
My appologies for not initially expressing myself more clearly and for any confusion caused.

cheers

Bob

 

[andersonec]

Bob,
There's a safe way to dig round trees and seeing if it rocks isn't a safe way, those larger roots are there for two reasons, one for stability (which you mentioned) and the second is the transportation of nutrients and moisture to the tree from the hundreds of fibrous roots that are attached to that root, those hundreds of fibrous roots are in turn fed by millions of root hairs which actually do the collection of moisture etc from the soil so when you cut one 25mm root you are doing more damage than you think, that 25mm root is not the one which is collecting the moisture/nutrients.

The root hairs which do the actual collection of nutrients/moisture are very fragile, there are some 400 per square mm, and if these are all killed by exposure to the air and being allowed to dry out it will do your tree no good at all.
If you need to cut roots then plan to do it when the tree is dormant, preferably when it is just waking up round mid march, if this is not possible then try to protect any exposed roots as much as possible, cover with hessian and douse with water every day.

Most trees will tolerate the removal of a few of their roots but there is a limit, especially when the thing is fully leafed out and in full growing mode, and the older a tree gets the less it will tolerate the removal of roots, especially those underneath the canopy.

A fully grown Oak will use circa 400 gallons of water a day ..............Andy

Hi Andy

Yes I know all that and of course you're right but I wasn't suggesting that the OP actually cut around and rock the tree My point (badly made) was that the roots at the surface are only a small % of the total root system (which is why it wouldn't rock).
The tap root and deeper roots are perfectly capable of supporting the tree and collecting nutrients and water and will actively seek out a moisture supply, which is one of the reasons they damage drains. I've repaired drains packed full of roots doing just that.

It's also one of the reasons why building inspectors will insist on very deep found excavation if anywhere near trees. Many extensions are built under the canopy without killing the tree!

Have to use commonsense but as I've said, I haven't lost a tree yet and I've dug around plenty, I also have 3 mature bramley apples which have been transplanted 3 times in 20 years and bear heavy fruit crops as well as a 10 year old oak twice and it's growing like hell!. It's also why bonzai root pruning is successful with almost any tree with care.
I'm not a tree expert btw, just had and have a lot of experience and love the things. I do a lot of ground works for other people which conflicts with roots. Had to take out 7 trees on my own land a few months ago which I didn't much enjoy though left one very large poplar with a 400mm trunk at 2.5 mtrs height to see if it will pollard and there's sign of life.
Amazing things are trees :lol:
My appologies for not initially expressing myself more clearly and for any confusion caused.

cheers

Bob

Bob,

I used to have my own plant nursery and just didn't want other people getting blaze' about digging round trees and cutting their roots.

Root pruning is a technique carried out by Bonsai enthusiasts for the simple reason to allow the tree to live in a tiny container, if the roots were not pruned the thing would soon push itself out of the pot. This is a technique which should be taught by all the 'TV' gardeners for keeping plants in pots, so many times I have delivered plants to people and seen trees, Acers mainly, looking very sorry for themselves and struggling to stay alive, when I ask them "do you feed it?" and "how long has it been in there?" the usual answers were "no" and "years" so then I would have to spout off and give them a lesson on how to re-pot in late winter.

Moving trees is not a problem if done at the right time and the right way, the Victorians used to do it because they couldn't wait for 200 years to see the thing fully grown, you can buy 20m high trees from some of the Italian nurseries and the japanese move large trees on a regular basis. Don't do it again before the tree recovers which is usually about three years, reducing the canopy helps when moving a large tree.

It was common practise to let Poplars grow to full height then cut them down to 2 or 3 meters, they would then regrow to form good wind-breaks, there are lots of trees which will tolerate being cut down and Yew is one of the best for it.

I know woodworkers have a love of wood and they should also develop a love for trees like yourself, a little knowledge of how they grow and why they do the things they do will help answer a few questions, I see a lot of mis-quotes about the purpose of the different sections of the trunk/leaves/roots etc.

Sorry for the rant by the way and now after all that I'm gonna get a bottle of beer and sit outside

Andy

 

[Lons]

Hi Andy.

It's obvious that you were in the trade when I see the pic of your beautiful garden. If you have 6 months spare, there's one here desperately needs some tlc :lol:

This is my 7th house. At all the others I managed to create really nice gardens, but not this one and I've been here 25 years Just can't find the time. A decent bit of land at around 1.3 acres but it takes me all my time to cut the grass these days and 4 days to cut the hedges as well #-o
It's on my "to do when retired" list along with all the other stuff :?

I grew bonzai for about 15 years. Everything from seed, seedlings from the wild to small shrubs from the nurseries. Tried all sorts and gave most away but kept 3 really nice specimens until my neighbour managed to "kill" them when we were in South Africa which sickened me off. I still have some of the books and a few tools and pots so you never know!

I absolutely agree, everyone should be educated in the art of root and branch pruning and read the basics of plant needs for good health.
Far too many healthy plants end up dead due to under / over watering / feeding by people who can't be bothered to educate themselves!

Hope you enjoyed your beer - my (2) were delicious :lol:

Bob