Tree wells and drainage

[t.phillips]

hi,
I wanted to ask the group if routing street drainage to sidewalk tree wells (or pockets) will encourage rotting of roots and trees or other problems? A current proposal calls for a 4 foot deep by 6' to 12'diameter stone filled pocket in a sidewalk,into which would be planted a tree. these pockets would be set such that the street runoff caught in the gutter would enter them until full. Once full the backed up water would continue to the existng catchbasin system. As planned, the tree would be rooted in the soil underlying the 4 foot stone chamber (with a 3'gap (tree well style) separating the trunk from the stone.

other than the rot issue(or others that I've missed) I wanted to know if there was a species of ornamental that could handle the innundation and droughty conditions?
thanks in advance
Tyler Phillips

 

[treeclimber165]

This sounds like an idea thought up by someone who has absolutely NO KNOWLEDGE of trees! My gut reaction would be ABSOLUTELY NOT! NO WAY, NO HOW! But then I would have to look at the site, soil types and species of trees and be familiar with the needs of trees in your area. For all I know, there may be some tree in NH that could survive and even thrive in your doctored up conditions, but it sounds like a liability waiting to happen in my opinion. 15-20 yr old trees with rotton roots over a road and sidewalk sounds expensive and deadly.

 

[John Paul Sanborn]

Most desirable street plants cannot take being in saturated conditions. anaerobic conditions take place, and roots need oxygen. If all you were planting is baldcypress, tamarack and silver maple then I would say it may work. But most every thing else will not.

ANy time you have a boxout with no drainage the trees do not last long. This looks like a design idea without any urban forestry consultation.

I think that all boxouts should have good sub soil drainage and species selection should lean towards drought tolerent plants. Most cityscapess are realy concrete and asphalt deserts anyway. Then plant them small and bare root so that the roots can be positioned properly.

Bassuk of Cornell has a study on bare root planting. Good paper.

City of Milwaukee Forrestry has som good studies on downtown street palntings.

here is their web page
http://www.mpw.net/Pages/dpw4.htm

 

[Kneejerk Bombas]

I would recommend those plastic trees they sell at department stores.

 

[t.phillips]

tree well follow up

Hey, a genuine thanks to those who responded (aside from the plastic tree idea-good chuckle though)to my question. I appeciate the candid responses to my question. Although I am not an arborist I do know a bit about the subject and certainly anticipated the root zone anaerobic issue, but it is good to see that I'm not being overly sensitive or conservative in being hesitant to implement the proposed idea.

Unfortunately there are many objectives of the project (of which tree health is probably about 4th or 5th on the list-but still quite important to some in the project). What I was (and still am, assuming I have not overstayed my welcome on this site) interested in finding out is presented with this a frequent saturation as a given, are there mitigation measures that could be employed to alleviate some of these basic problems? This is an out of the box project to begin with so please let you imaginations run a bit. (We have even consider small aeration units at the root zone powered by solar charged batteries).

Would for instance a stabilized planting tub (with holes cored in it) for the root ball set in the surface of the stone pocket work? or is this so limiting to root development (roots would not likely exit holes to flourish beyong tub)that the tree would be stunted and just approximate street trees set in the barrels sitting on the sidewalk?

To pick up on the silver maple idea can anyone add some more trees to that list.

Sorry for the Pe(st)cistance, I just want to make sure I flush out all of the options and kick over all of the stones. If it is not do-able that is fine I just want to be sure.

Thank you
Tyler Phillips

 

[Kneejerk Bombas]

I don't know if this a consideration where you are, but around here, road de-icing salt would be a big problem for your planters, not to mention other road contaminants. Did you ever look at road runoff?

 

[Tom Dunlap]

Time to start building a fire or a gibbet. I'm going to espouse heresy here. Bruce Cockburn says it better:

Tie Me at the Crossroads
Chorus
Tie me at the crossroads when I die
Hang me in the wind 'til I get good and dry
And the kids that pass can scratch their heads
And say "who was that guy?"
Tie me at the crossroads when I die

Looking outward see what you can see
By the time you look at something it's already history
As the echoes of our passing fade, all there is to say
Is, "You know I loved you all in my particular way"
Chorus
It's more blessed to give than it is to receive
Except when it comes to free advice I believe
Here I go anyway, back seat driving tonight
Move fast, stay cool, keep your eye on the front sight
Chorus

There are sites where we want trees to grow but the site is not where trees want to grow. Even though I despise throw-away planning and the disposable world we live in, I have an idea for sites like this. Instead of thinking that you have a hope of growing a tree to maturity on this site, think of it as a three, four or five year petunia. Plant now, when the tree dies, plant another one. Sometimes the battle isn't worth the fight.

Sounds like you're trying to develop some sumps to hold some of the run off water. I gather that you've done the hydrological calculations and figured out how many cubic feet of water to expect after any rain in quarter inch increments. If so, its hard to imagine how you could have enough of these tree sumps to have any meaningful effect on the amount of run off. Reduce the hardscape or make holding ponds.

Tom

Make my noose out of Yale Peppermint

 

[t.phillips]

Yes sir,
As a matter of fact the salt issue was probably my first overiding concern. I thought however that there may be some way around it through species selection or as a last resort through the application of wetting agents. When compared to the saturation issue the salt issue seemed more surmountable.

This leads to another general question, are wetting agents or other practices effective at ( what I undstand to be) supplying nutrients to the roots in soil that has high salt content (and resulting osmotic (?) inbalance).

Thank you,
Tyler Phillips

 

[Jay Banks]

The principle is sound - bio-retention - It just sounds as if there is a need to educate the engineer designing the "system". I have seen similar systems established in parking areas the receive salt treatments, pollution from dripping oil and antifreeze. They do work.

Take a look at
http://for.communitypoint.org/pages/grogreen.html
http://state.vipnet.org/dof/rfb/riparian/rain_gardens.htm

 

[John Paul Sanborn]

The easiest means for salt mitigation is flooding. Salt is veryu mobile in the soil so it can be washed out with H2O.

There is no real way around the drainage problem.

Why try to re-invent something other muni's have gone through?

"Arboriculture" 3rd ed, Harris et al, has a chapter (10, on pg 270) special palntings, dealing with street palnting , raised boxs....

I don't look into downtown urban forestry much, but as Tom states it is more of a short term aestehtic issue. A very harsh environment, with many hazards to the tree; cars, people, heat, pruning needs....the urban desert.

Some of the othere things you may want to look into are the structured soil studies that ahve been going on.

Raised planters have an additional problem of freezing roots

Then you need to look at the growth habits of the trees you want to plant, cant have a wide spreader a few feet from a tall building,you just end up having to hack them up to conform to the space look for cvs with names like 'Fastigiata', 'Pillar' and such.

 

[Jay Banks]

And take a look here on salt tolerance

http://www.extension.umn.edu/distribution/naturalresources/DD1413.html#Trees