Willow problem, recently slabbed around

I have a 20yr old American purple stem willow tree about 9 or 10 foot tall by about 9ft diameter shaped like an umberella. Apparently this type stay fairly small which is why I chose it. Its leaves have started to go yellow mostly at the ends of branches. Not sure if its because of the new slabbing around it, that it will be much getting less water or if its normal for the leaves to go yellow at this time of year?

I have just had slabs put all around the tree to extend the patio area and while this was being done some of the roots (I'm pressuming it was the roots from the willow) were chopped as the area was dug to 6 inches deep before the slabs were laid so it has lost 6 inches of top soil over a 15ft by 15ft area (willow in the middle). The gaps between the slabs have been filled in and under the slabs will now be the sand and cement mixture which was put in all the corners of each slab so there will be gaps under them too with no soil.

I don't really want to lose it, next to the trunk which is approx 8 inch diameter at widest bottom point there has been left quite a small soil area about 15 inch square including the trunk.

Could it be that it has to recover from the roots being chopped a bit or will it be the sudden lack of water? I thought with it being there for 20 years that it might withstand this as its root system was well established. I thought the roots would find thier way to the outside of the slabs where there is grass. Will it recover?

It was previously surrounded by grass

 

Hi Lady Gardener,

Roots are highly sensitive and should generally be left well alone if you want to keep your tree healthy. Just a few quick points about the importance of roots to your willow tree.

1. The majority of the water absorbing root hairs are found withing the top 12 inches of soil and extend out as far as the tree crown. These fibrous roots are important as they absorb the water and nutrients from the soil and the larger, thicker roots then transport that water to the tree. Many people think the small, fibrous roots are not as important as the bigger root system, when in fact it's the other way around. By removing the roots and soil you are reducing the root's functionality.
2. The area around the root is called the rhizosphere and is where the tree root/soil interaction takes place. There is often a fine balance of beneficial fungi/bacteria in this zone which aids the tree with its water and nutrient uptake. Disturbing the rhizosphere can lead to tree decline.
3. As you stated; by slabbing around the tree you are reducing the amount of water the tree will now be able to absorb. Trees grow according to the amount of water and nutrients available to them. By suddenly reducing the amount of water your tree is able to get you are creating a defecit which can lead to tree decline.
4. Trees need oxygen in the soil in order to do well. Tiny pores in the soil contain pockets of oxygen that the fibrous roots absorb. Slabbing over the soil compacts these pores and reduces the amount of oxygen available to the tree; again resulting in poor tree health.
5. Biodegradable matter such as leaves, mulch and dead fauna/micro-fauna rot down at the base of the tree and add vital nitrogen back into the soil for the tree to absorb. Slabbing around the tree will not allow this to happen.

There are more factors but I hope you get the gist. A yellowing of the leaves is a sign your tree is suffering stress brought on about by recent changes to its conditions. Unfortunately many people are simply unaware of the importance of roots and fail to get a professional opinion before starying work. Instead they will only ask for help once work has been carried out, often which is detremental to tree health, and then ask for help afterwards.

 

Thankyou,

Well unfortunately I am one of those people that did not realise the impact that the changes would cause to this tree, I overestimated its strength being 20 years old but now realise there is more to it.

Its what to do now though if anyone can advise me, I know removing the slabs and cement and replacing the soil would be the best solution but I'm trying to avoid that if possible because its cost a lot of money and 3 weeks to do it and then I guess it wouldnt be 100% sure to bring the tree back to full health if they were taken up. If they had not been cemented down I would have but it would be a big job now.

The crown doesnt stretch to the lawned area either. So basically is this totally without hope of recovery?

I could water it in the open trunk area but would it help it to build up the fiborous roots again? Could I feed it with something? Would trying to remove the cement from between the joins help enough with water and oxygen? Is there any hope that with any help the tree might extend its roots to the lawned area gradually? Should I trim the tree so it reduces its need for as much water at the moment? The closest soil is about 2.5 metres away just at the edge of its crown which runs all the way down my garage

 

I wanted to try and do something so for the time being I have watered it around the trunk in that little square of soil and all over the leaves then I noticed the tomato feed has nitrogen so I put on 1 capfull in 1.5 gallons of water. I know its not going to do a miracle but I can't do nothing.

As far as the oxygen is concerned I don't know if it makes any difference but the slabs were not laid flat on top of the cement the cement was put in blobs in the 4 corners of each slab so there is some air under there because of the gaps.

As I was watering it I thought would it help to take out the soil from around the tree trunk because it would then leave a depth of 6 inches and the gaps between the slabs in the square around it would be more open and when it rains water would get under there more easily although I know not like before it was done. I'd just fill the hole with some granite stones I have that wouldnt slip between the gaps instead of the soil. I could even shove the hose pipe down between the slabs from time to time if it helps, do you think this might do any good?

 

Not sure where you live LG but its been a dry summer here, add to that whats gone on around your tree and I'm not surprised its acting up a bit.
I Think watering is probably a good idea, perhaps a hose left just with a trickle of water at the base where you still have visible soil has got to help a bit.
Not sure feeding is worth it at this stage though.

Just hope to keep it alive for the rest of the summer until we get the winter rain, and it might just pull through.

 

Hi again,

Your tree will probably be OK. It won't achieve it's full potential, but willows have a nack of hanging on in there when all other trees give up. Unfortunately willows do have quite a thirst and are highly water demanding.

The tree may extend its roots in order to locate water, so you may find that the root system develops further than the patio. Watering at the base of the tree will provide some help, as this is what happens to street trees when they get paved over.

I think you're just going to have to wait and see what happens.

 

I have the impression that paving an area, after the initial upset, actually holds moisture and cuts out the competition.

So if your tree can pull through this summer, I'm sure it will have masses of rooting area all to itself.

 

Thanks,

I have continued to water the tree around its base, it doesnt look fantastic but its looking as though its hanging on and at least has a chance, its not going to be easy to judge anyway as its getting towards the end of the season and it will lose its leaves anyway soon.

I don't water it every day though as I don't want it to get water logged under there as it is quite near the house too, about 12ft away probably. And I don't want the slabs to start moving by having too much water under there. I was pushing the hose under the slabs but I'm not going to do that any more I'll just water the base. It is near a sewer though, it will be really close to it as it runs in between the tree and the house so hoping that wont get damaged.

I will be hoping for signs of life in the spring next year, if it does not survive I'll have to plant something that will grow over it or take it of completely and fill in the hole where it was

 

Just a quick question: Have you considered what you are going to do when the roots start lifting the patio slabs as they search for water?

 

Well no I was hoping that might not happen, I hoped as there is a gap between the soil and slabs where there is no cement they might give up going that way. I can only think about that if it starts to happen, not sure what I'd do

 

Did you put any sand or cement down when you laid the slabs?

 

It was mixed up sand with tiny stones in, sharp sand I think with cement then put into piles in each corner where the slabs went, the rest was left just as compacted soil about 5 or 6 inches deeper than it was originally

 

No plants or trees like the lime in cement leeching into their roots and there can be "all sorts" of stuff in builder's sand.

 

Oh gawd does that mean its inevitable that its going to happen?