Root barrier for new plantings

[Jesse]

The attached photos show the last lot of transplanting and the root barrier. The barrier has since been moved out to give the roots some room to establis. We are finding that roots will not penetrate the pumice level because it is so hard and deep. They call it a pumice pan. There is no soil below for, in places, over a 100m, and in Taupo and Turangi for as far as you can dig after the first meter pretty much. I had a fence put in at home and they hit pumice less than 0.5m down when digging holes for the strainers. Working on the basis that the root barrier is to encourage the root to grow down but the pumice pan prevents this...........are we just going to end up with stunted trees?

 

I'd say yes you are going to end up with stunted trees, but in that situation I would say that thats ok, BS standards or recommendations or any other uk documents will really have little relevance where you are, volcanic subsoil ? I will try and explore the issue more, things looking good for you over there ?, mines a V B one day maybe .

[Taupotreeman]

A VB? c'mon, you can do better than that

 

That's the problem I'm finding with all the info on the web. Nothing really applies because of the pumice layer.

[Jesse]

A VB? c'mon, you can do better than that

 

That's the problem I'm finding with all the info on the web. Nothing really applies because of the pumice layer.

 

Now whats wrong with a V B ? I know, I,l give it to you that you serve it in a frosty glass raped in a doily , on a hot day after a hard one which was EVERY DAY out there, it was a quality treat , BUT WHY NOT MAKE IT A PINT ? i can't remember the sizes but they were pretty shoddy

[David Humphries]

My queries are; the trees will be growing in a pumice pit (due to layer upon layer of ash deposits from volcanic eruptions) so the roots cannot grow down, as in some cases with root barrier. Council is wanting full size specimen trees. What will the effect of the barrier be on the root growth? Will the trees be limited in size (presumably they will be) because of what will basically be a root barrier on all sides including under?

 

 

How about moving away from trying to establish new trees in the available poor rooting environment and creating bespoke above ground containers which can have an increased nutrient rich soil volume.

 

I think i read somewhere that Singapore brought in some massive container trees for the duration of the Grand Prix, which they removed back out to storage until the next one. These were pretty large trees from what I recall.

 

Might be worth having a look at that as an alternative strategy

 

 

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[Taupotreeman]

We had some David. They were in large metal containers and were approximately 4 to 5m tall with trees. They were planted with London Plane, Cherry and Liquidambar. They were moved around the town from shop front to shop front by HiaB and flat bed. The powers that be got bored with them after a while and, apart from two that a local cafe adopted, the rest were dumped in a reserve, still in the metal tubs, forgotten about and left to die. We have managed to save all but one and the current plan is to gas axe the tubs and plant them in the reserve this winter.

 

Unfortunately, we, the arborists, are seen more as chainsaw hacks and are at council for nothing more than keeping service requests to a minimum. The project manager, landscape architect and community board all want instant tree and rather than planting a tree to suit the environment (I.e. shallow soils and hard pans) they want large specimen trees with no root disturbance to roads, footpaths etc. it was suggested that we plant smaller growing Acer species that would maintain the colour but have less issues. We are already being asked to remove a lot of the Oaks by property owners due to leaves, acorns, shading, roots in the lawn and drive etc.

 

Yeeesh, my last few posts here and with the root pruning, are very negative but it seems we are constantly fighting an up hill battle and it does wear thin after a while.

 

 

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[Taupotreeman]

I'll take some photos of the site, that might help a little.

 

 

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[Paul Barton]

Interesting thread - I feel your predicament T'man. Sounds like an all too familiar situation where the person that really knows and cares about the trees long term, hasn't been given the political and financial clout to make the important decisions! Still, you can still lay the facts (?) out straight to your council officers.

 

A tree with a restricted rooting volume cannot reach its full potential, either in terms of life span or ultimate height.

 

I think the starting point is to ask your colleagues what kind of tree-scape they are aiming for. If they want large canopy trees (which generally provide the greatest benefits) they have to accept that large soil volumes are needed.

 

James Urban's book 'Up By Roots' suggests that a rough guideline is 1-3 cubic feet of soil per square foot of tree canopy - the lower figure being for a well-irrigated soil and the higher for a drier soil. He doesn't quote a source for the soil volume calculations so I can't say whether it's made up or well researched but using his calculations:

 

If your barriers are 2.5x2.5x0.6 (metres) that's a s volume of 3.75 cubic metres or 132 cubic feet. So, in an average soil you could assume that for every 2 cubic foot of soil you'll get 1 square foot of canopy....132 cubic foot might therefore support a tree 11 foot tall by 6 foot wide (based on a simple rectangle area).

 

That's a small tree!

 

It may well grow larger than this but I think the suggestion is that it will be running out of steam from that point.

 

Of course this is only considering the volume of soil....it is advisable to also assess the soil for its structure, nutrient content, water availability and so on.

 

If the main concern is future damage to pavements, how about using a structural cell system to provide a greater soil volume and support the hard surface? It has to be said that the author of the above book has a vested interest in recommending this system as he designed them but they may work for you as you could install the root barriers much further away around the edge of the cells.

 

Silva Cell Tree And Stormwater Management System From Deeproot

 

Of course any technical solutions come with a price tag - so it's back to the question of what the end-game is. If smaller trees that will need to be replaced every 10 years are acceptable then you could stick with the tiny pits but if bigger trees are required some innovation and $$$ is needed:biggrin:

[Gary Prentice]

Interesting thread - I feel your predicament T'man. Sounds like an all too familiar situation where the person that really knows and cares about the trees long term, hasn't been given the political and financial clout to make the important decisions! Still, you can still lay the facts (?) out straight to your council officers.

 

A tree with a restricted rooting volume cannot reach its full potential, either in terms of life span or ultimate height.

 

I think the starting point is to ask your colleagues what kind of tree-scape they are aiming for. If they want large canopy trees (which generally provide the greatest benefits) they have to accept that large soil volumes are needed.

 

James Urban's book 'Up By Roots' suggests that a rough guideline is 1-3 cubic feet of soil per square foot of tree canopy - the lower figure being for a well-irrigated soil and the higher for a drier soil. He doesn't quote a source for the soil volume calculations so I can't say whether it's made up or well researched but using his calculations:

 

If your barriers are 2.5x2.5x0.6 (metres) that's a s volume of 3.75 cubic metres or 132 cubic feet. So, in an average soil you could assume that for every 2 cubic foot of soil you'll get 1 square foot of canopy....132 cubic foot might therefore support a tree 11 foot tall by 6 foot wide (based on a simple rectangle area).

 

That's a small tree!

 

I think the pits are circular, with a 2-2.5m radius, so the soil volumes a fair bit higher. But the sort of size the council are looking to attain (judging from the residential area photo) are planted in verges. From what was said earlier, those trees were planted forty years back, so it's quite possible there were/are no barriers to radial root spread.

 

If the intention is to plant trees that are going to reach maturity, a much more expensive, engineered solution is going to be necessary.

[Paul Barton]

Ah, sorry about that.

 

On the same basis the pit would have a volume of 416 cubic feet. On the basis of 2 cubic meter to 1 square meter of canopy that would give you a tree with a canopy of 208 square metres.....that's still only 20ft by 10ft plus the height of the clear stem.

[treeseer]

not really clear on why holes were not dug deeper to increase soil volume.

stunting scenario seems possible--hope you are retired before.

jeez i thought i had problems with clay...!