Old trees fertilizing methods

[tomstrees]

A customer had this 150 year old oak tree with very little in the way of real foliage, mainly sucker growth. She was hoping that something could be done to re-invigorate it. I got the best organic fertilizer, low nitrogen and it did not seem to help.

I guess the message here is don't do anything if you don't have the solution? Is there anything that can be done with trees that are still standing but showing little in the way of real foliage?

 

[ATH]

diagnose the cause of the problem if possible (sometimes quite the challenge...).

are disease or insects involved?

Has there been a change to the soil/roots?

 

[tomstrees]

150-200 plus year old trees are not something that can be reinvigorated much right? The only sensible solution is to either leave it alone or maybe top dress with humus rich soil, others here would know better. On this request by a customer I used an organic fertilizer, some lime, etc.. Customer wasn't happy that i couldn't work a miracle with a tree that had been in decline a long time.

 

[ATH]

I wouldn't say they "cannot" be reinvigorated. Too many variables. Certainly, there is no miracle cure/fast turn around. Soil quality is very important. As go the roots, so goes the top. A big shot of N may give it a quick greenup, but that may not be a good thing for the long-term as it forces the tree to push top growth at the cost of roots and defense compounds. I recommend against it.

Paclobutrazol may be a better help than fertilizer.

Soil decompaction and incorporation of organic material may be a better option.

First, look for pests attacking the tree. It may be something as "simple" as a bad lecanium scale or obscure scale outbreak, for example. If you aren't looking them, they are very easy to miss. If that is the cause, this is probably the closest thing you'll have to a quick turn around.

Second, has anything changed with the soil in the last 10 years? Construction, new driveway, replaced sewer drain, etc... Or has there been ongoing compaction - even a lot of foot traffic in parks will cause compaction issues.

Third, do a soil test. Is anything in short supply? What is the pH (certainly figure that one out BEFORE you put lime down! - many urban environments have a pH that is already too high)

Then, start to put those pieces together to come up with a treatment plan. That may involve periodic hazard reduction pruning. I point out to people "if this tree has 10% of its life left in it, that is 20 years!"

No shame in bringing another arborist out to help with the plan. Where are you located? @guymayor travels helping people do just that with historic trees.

 

[guymayor]

Absolutely they can be reinvigorated. Topdressing just scratches the surface lol of what the soil needs. I often fracture subsoil 2'+ deep and blast in compost etc. to deepen soil volume and increase drainage.