Parched Japanese Maple in Zone 7 (Queens, NY)

[Enlight]

Hi folks, thank you in advance for any advice.

 

I have a Japanese Maple that has been losing limbs and branches. It receives full day sun and has nothing shading it from the south. Its brother on another side of the property is flourishing. We hired an arborist a few years back and his assessment was this tree was not getting enough water. I have since undertaken some rainwater harvesting measures in the form of storing rainwater for hot days, redirecting our downspout to feed the trunk of the tree, and also re-routing runoff to infiltrate into nearby earth.

 

While I have spotted some new tender growth (spotted on the ground after squirrels gnawed them off), I'm not certain the overall health of the tree is improving. Is there anything in the way of soil assessments I should be looking at in order to help this tree? The pictures shows bare soil at the base which I just aerated before putting down pine bark nuggets. The mulch that was previously there completely decomposed and even caught fire last year.

 

 

General View

 

Westerly Facing Dead Growth

 

Easterly Facing Healthier Growth

 

Trunk (will soon receive pine bark nuggets)

 

Trunk Bark

 

New Growth

 

Water Harvesting

Edited May 20, 2022 by Enlight
Formatting and captioning

[Steve Bullman]

Thats a pretty poor environment for that tree really, and I wouldnt expect it to thrive there. You mentioned the other tree is doing well...i'm guessing its not growing in quite the same environment?

[Enlight]

The other tree receives more cover from the afternoon sun. I've come to accept the site location is not ideal. Unfortunately, that's where the tree was when we purchased the house. Perhaps there were other trees giving it cover in the past.

[Bunzena]

I agree that it's not in the best position for a Japanese Maple.  Although I can't be absolutely sure about the variety - it looks like an Amoenum group 'type'.  In my experience these aren't the biggest fans of direct sun with their delicate leaves.

 

Likewise, the planting medium/position looks pretty tough - set, as it is, in a block paving circle with a slightly raised soil level. 

 

However, this is a very mature tree and has clearly been happy enough to reach this size despite the exposure and any other factors.

 

And the leaf tips don't show any signs of scorch or browning.  The fist sign of sun/wind damage. 

 

Instead - it looks like 'die-back' - where whole branches just die-back to a point on the main stem.  This isn't uncommon on Japanese Maples and could have a number of causes.

 

Here in the UK where we live - this could be frost damage.  Recently late and sharp frosts when our Acers are coming into leaf have had this affect on a small number of trees.  Leaves are hit and then branches can die-back to the main stem.

 

The second cause could be fungal/bacterial infection - which, again, is common in Acers that are under stress.  Stress perhaps caused by a recent hot [and windy] summer, maybe pollutants running off from your drive into the soil, lack of water or a change in soil level around the tree. 

Ironically it also be caused by too much water.  Many Acers are mountain trees and like moisture - but free draining soil too.

 

Once stressed, the most likely culprit here would be Phytophthora or Verticillium.  One way to check would be to look at one of the affected branches and see if there is a colour change of the younger bark, near the top and near the die-back.  If so this is a good indication of fungal infection.

 

If that is the case then the best approach is to remove the branch right back to the main stem.  I will also treat the cut surfaces with a fungicide to try and prevent further spread.  In the past using an old-fashioned, copper-based product has worked best.

 

If Phytophthora or Verticillium progress too far into the vascular system  - you may lose the tree entirely.  So be prepared to be ruthless with some pruning if this diagnosis is correct.

 

Alongside all this I'd also look to give the tree an easier life.  Check you aren't under/over watering.  Maybe remove some of the soil and top-dress.  Perhaps open-up that locked-in circle of stone it lives in.

 

Hope some of these suggestions might help.

 

[Stubby]

The fact that the previous mulch caught fire won't of helped the roots .  Could pine bark mulch be too acidic for this species ? I'm no expert .

[Enlight]

Thank you for your thoughtful responses.

 

In response to Bunenza... I, too, am surprised that the tree was happy to grow to such a size before these ailments. It is still mid-late spring and it will be summer before the scorching begins - it has suffered from scorching in the past. I am fairly confident that the tree has good drainage as we have sandy free-draining soil here. It does not receive any runoff from the drive as it is up slope. I have thought about removing those paving stones in order to create a "swale" to capture more water during rain events. There is never any standing water here due to the topography, I am almost certain this tree is not waterlogged.

 

10 hours ago, Bunzena said:

Likewise, the planting medium/position looks pretty tough - set, as it is, in a block paving circle with a slightly raised soil level.

...

One way to check would be to look at one of the affected branches and see if there is a colour change of the younger bark, near the top and near the die-back.  If so this is a good indication of fungal infection.

Is there anything I should be aware of with soil levels? What kind of colour change should I be looking for. I haven't seen any so far, just lichen.

 

7 hours ago, Stubby said:

The fact that the previous mulch caught fire won't of helped the roots .  Could pine bark mulch be too acidic for this species ? I'm no expert .

Luckily it was spotted quickly by a delivery driver. What had happened was the small dendritic roots of the tree grew so dense that it trapped the heat from direct sunlight. In any case, it was put out quickly and didn't touch the trunk of the tree or any large roots. I later loosened up the soil with a handrake. What I've read is that pine bark rarely changes the pH of the underlying soil, though Japanese Maples prefer slightly acid soil anyway.

 

I've also attached a picture of my healthy maple.

[Bunzena]

1 hour ago, Enlight said:

Is there anything I should be aware of with soil levels? What kind of colour change should I be looking for. I haven't seen any so far, just lichen.

In my experience, Japanese Maples don't seem to like the soil piled-up against the main trunk.  We have a collection of nearly a hundred in the ground that were all originally in pots.  We took care to make sure that none were planted deeper in the soli than the level they were in those pots.  However a few inevitably ended-up deeper and they did seem to struggle.  If you had added too much mulch - that just might be an issue.

 

As an aside - a small amount of pine bark is fine - and that Acers don't mind the minor acidity that brings.  Just not loads.
 

The colour change that occurs with fungal die-back is only evident to the bark before it thickens and becomes woody.  New stem growth or last years stem growth that may well be green or light brown on the variety you have.  So you'll have to get up into the tree or remove a section high up.  It's not evident lower down on the old wood. 

 

Generally the branch starts to develop a brownish, reddish or yellowing tinge to the stem that then travels downwards as the infection is being fought by the tree over a period of a few weeks.  Once you see it - you'll know it. 
 

If die-back is due to something more mechanical [such as frost damage or desiccation] then this colour seems to be absent.  
 

The tricky bit is that you have to catch the colour change as it happens.  Once the branch is dead - it will all look brown.  I've uploaded an example of a fungal problem, the indicative colour change and the dieback.

 

Hope this helps.