Shagbark Hickory preservation

[Rooted.Tree.Solutions]

I’d love to get all of your thoughts on a project that I’m looking at. There is a Botanical Graden in my community that recently underwent a huge construction project where they built a new visitor center and event venue. I don’t really want to get into all the mistakes they made when they did this project, what’s done is done.

So, there is a mature Shagbark Hickory tree that sits in a very prominent position for guests entering the park. It is also right next to the new visitor center. They broke ground on this building in the Spring of 2023. The soil around this tree was disturbed then, compacted by construction equipment, most likely had roots cut when they installed the sidewalk that goes near the tree, then had dirt piled on top of the root zone and buried the root flare. Construction was completed and the new visitor center opened in the Spring of 2025. The tree is showing obvious signs of stress and has tip die back happening in the upper canopy.

The gardens have recently hired a new superintendent and he is passionate about preserving this tree and recognizes its importance, if nothing more than to communicate to the community that their botanical garden understands the value of trees and is willing to do what they can to preserve them.

I have suggested that the area be air excavated to expose the root flare and regrade the area back to its original height and haul away excess soil. Then, top dress the entire area with mulch, apply a tree growth regulator and amend the soil with plans to fertilize the tree for the next several years.

I’ve never personally done a project in which I’m regrading and removing soil from a construction project, although I’ve read about it being done. Curious what your thoughts might be.

(I don’t know why it’s uploading my pictures sideways?)

 

[Matias]

I endorse your plan. Also, see if you can find a local source of high quality compost or worm castings. Don't buy the shit in plastic bags, as that is starved of O2 and very much compromised. It will almost certainly be very expensive, but you just need about a bucket worth, though make sure you transport it in a burlap sack so you don't suffocate the biology within. Stir about a quart per 5 gal bucket of water and spread it out to the entire root zone. If you need to scale up the process to do more area, I can send you plans for a commercial sized "tea brewer" that can ride in a trailer.

 

[Analog]

Seems like a good plan, though I question fertilizing a compromised and stressed tree. I'd also add vertical mulching while you're in there. Incorporate biochar into that and the backfill mulch.

What a frustrating issue!!! An ounce of prevention... and all that. Are they open to going a step further and fencing off the improved area to avoid future compaction, at least for a few years?

Best of luck to you. As I liked to say back when I was heavily involved in municipal plan review and tree preservation during construction, simply not removing the tree is not equal to tree preservation.

 

[Reach]

I like that idea, definitely putting a good quality mulch of some variety down after the excavation, and I am all for fertilization of that tree but with a mild fertilizer of some variety. I like the idea of compost tea or something along that line, maybe a good composted (Not fresh!) manure if you are in farm country. If you have to use a chemical fertilizer, use a mild one, and don't use too much of it. You're trying to give the tree a little bit of a boost, not such a shock it can't handle the "nutrients".

 

[ATH]

I like your plan and other comments with a few thoughts:

I don't know what the "right" answer is for soil removal. I don't want skid loaders running all of the the root zone again. But how else do you get that much soil out of there? Air Vac? Still a lot of dirt to move.

Also, I see the pond...was that there before, or a new addition? Be careful about getting soil, compost and fertilizer into the pond!

If soil removal is impractical, area-wide air-tilling. Part of that should be deeper holes for the vertical mulching piece. I don't know that you need to put anything into each deep hole. I would mix Biochar + compost in if you are air tilling the whole area.

Soil test to see if any nutrients are lacking. Only fertilize if so. Otherwise, I'd hold off on that. Maybe some Reliant Dry Phite instead of other N-P-K products to help with disease issues?

Perhaps a liquid/bio aeration product as well? The compost kick soil microbes into high gear should help there, but maybe a specific target application will help.

 

[Analog]

It doesn't look like too large of an area for humans with wheelbarrows to get dirt out, after air spading. Or a mini skid and a few ground protection mats.

 

[Matias]

It doesn't look like too large of an area for humans with wheelbarrows to get dirt out, after air spading. Or a mini skid and a few ground protection mats.

I didn't want to be that guy, but as a micro operator with minimal equipment, I would haul the dirt away in a wheelbarrow by myself if I was allowed that time. I would hate to see any equipment driven in there again.

 

[southsoundtree]

Agree with all.

Test before fert.


How much soil was added?

Mats decrease psi. Tracks are low psi when not loaded down putting point loads, but some mats/ ply abs staying off the restored area is sensible.

Maybe a Carefully operated mini-x with a wide bucket to skim, using a spotter, perhaps.

 

[Rooted.Tree.Solutions]

Thank you for all the feedback! The excavation work would be all air spade and hand tools. It’s really hard to say how much excess dirt is there.

In regards to “fertilizer”, I should have been more clear. I use that term with my clients because it’s easier for them to understand that than “soil amendments.” I would be amending the soil with a biochar and humate mixture. Soil testing to determine if there are any other needs.

 

[The Green One]

Considering the Carya ovata has a deep taproot, and the stream is nearby, that likely helps a bit to offset soil volume losses from roadway work.... for rooting. (sustainability)

I would approach this project in 2 steps.

Step 1: would be to air spade/de-compact 3 feet out from the Root collar entirely, and then continue to "Radial Trench" technique from there, outward reaching to within 3 feet of the roadway and beds (leave turf buffer strip for sediment catch) making each trench the width of about a foot wide and 8-12" deep. A tree size you may have 10-12 trenches in total. Star pattern.....

This would preserve any "Fine roots" that have reestablished after the low/no oxygen poor gas exchange period when soils were once piled up within the Critical Root Zone.

Being mindful of the summer heat period happening, you would not want to compromise any more fine roots for now.

Radial air-spade trenching on foot, then backfilling with a quality hardwood mulch/biochar mix seems safe for this time period. (As Reach mentioned stay away from fresh local farm composts to avoid the pitfalls of SALT's/ High E.C.)

Step 2: In the Late fall air-spade the remaining CRZ entirely, only leaving the 3 foot turf/plant beds along stream/creek and roadway buffer, when the soil temps are around 45 F (Thanksgiving time in NJ) and thus fine root losses will be the least concerning.

Mulch/Biochar the remaining area in the CRZ to a 2-3" depth.

Reliant (Potassium Phosphite) is always a good idea with a stressed tree at least from my personal BMP's exp. A tree that size I would mix up a gallon of "label rate" mix and soak the trunk from the root collar up to 6 feet from the ground and any remaining mixture around the root collar.

Also it's never a bad idea to soak the CRZ now with 1/2 pound bag of Rhizofuel into 50-100 gal of water as a Drench.

I agree with others, steer away from any salt based ferts for now.

Best of luck moving forward.

 

[ATH]

...

Reliant (Potassium Phosphite) is always a good idea with a stressed tree at least from my personal BMP's exp. A tree that size I would mix up a gallon of "label rate" mix and soak the trunk from the root collar up to 6 feet from the ground and any remaining mixture around the root collar.

...

You ever use Dry Phite instead of mixing up the liquid?

 

[southsoundtree]

Digging some test pits may indicate the depth of added soil. More info at the start of the planning is better.

 

[The Green One]

You ever use Dry Phite instead of mixing up the liquid?

I have not ATH.

I just read up on it a bit @ Quest's webpage. VERY interesting that it releases over a 3 month period with rainfall OR Irrigation.

I'm going to order some. Thank you!

 

[Evo]

I’d start off with a half day exploratory work. The soil interface should be apparent. Ditto on RCX just to an archeological style dig to get an idea of how much fill there is.

Soil weight itself can add to compaction beyond equipment weight. If 12” of fill I wouldn’t worry too much about mini skid traffic to forward hand excavated fill.
Radial trenching is better than vertical mulching, and if possible I’d go with bio char and compost amendments.
Sometimes I’ll spec a detailed dead wood removal, to get the tree on a monitoring baseline.
Go slow if possible and increase or adapt as needed Vs hitting it with another sludge hammer

 

[Luzl78]

All they needed to do is protect the area with construction fencing. Builders are ignorant and not thinking ahead of the cost savings and the time it took for that tree to grow to that mature size. I love hickory trees.

 

[Rooted.Tree.Solutions]

*UPDATE*

So, some preliminary excavation with hand tools has revealed that the root flare is deeper than 15” down. The Superintendent is feeling like the project is hopeless. Do any of you have any experience/success stories with a restoration project like this? I’d love to find a way to convince the superintendent that there’s hope for success.

 

[The Green One]

I would not say hopeless.....

Years ago some Acer planted were in a similar situation (Acer are surface rooters btw) and I recommended that an Arborist with an Air spade, removed soil within 3 feet of the trunk, and to the depth of the Trunk/Root flair. When it was completed it looked like a Bowl shape.

The Deeply planted Acer responded well in a single season, and no further dieback in the canopy since the removal of extra soil was done.

Had it not responded well, I would have pushed for Radial trenching, outward to each trees drip line.

Remember we want the Root Crown/Collar to be able to dry out....

 

[TreeCo]

I believe the soil was added so the pond could be built.

Without correcting the poor drainage situation my prediction is that the hickory is doomed.

It's drowning.

 

[The Green One]

Any chance this Hickory is a Shellbark (Carya laciniosa) and not a Shagbark? I can't quite make out the leaves in the Photos.

Shellbark much better tolerance of wet soils....Reference: Silvics of North America Volume 2. Hardwoods.

 

[xovrin388]

15 inches of fill is insane, no wonder the superintendent is losing hope! But don't give up on it just yet. The Green One's idea of creating a sloped 'bowl' around the trunk with an air spade to let the root collar breathe really works, I've seen deep-buried oaks recover after doing that. Definitely worth a shot before calling it a loss!