Mature Pin Oak stressed

belter

Hi,

First of all thanks for the great forum and info, this is my first post. I have moved to a property which has a mature pin oak (50-60 years old) in the back corner which has struggled with the ongoing SE australian drought. The canopy is quite sparse and there is plenty of dead branches through out but nothing major is dead. The leaves are very small and the crown is thinning out also. No major construction or change to the trees enviroment has happened in the last 3 years. To help it out I have removed all the turf around the tree and mulched out as far as i can practically, fairly close to the drip line. The trees dripline is rather large so i concentrate my watering to about 1/3 of the trees canopy and water once every 2 weeks or so in summer. The ground is sloping and quite compacted. The tree seems to responding to this treatment a little but i am wondering what more i can do to help save it? It has put new growth (endormic?) on the main trunk which i understand shows stress. Is it worth trying fertilizer injections aeration etc, or is the tree just going to keep decling now it has been stressed for so long?
Thanks in advance.
PS i have applied plenty of seasol, does it really work?

treeshaveneeds

If the ground is quite compacted, wouldn't it make sense to de-compact the ground, and allow more water to penetrate, and have a better air exchange for the root systems?

On jobs where I have been asked to decompact the ground, I have found 1"-2" diameter holes on a 1 ft x 1 ft to 2 ft x 2 ft (depending on the compaction) has been beneficial, generally drilling the holes about 6-12 " deep, and using an airy organic mix to enhance air exchange, and augmenting with liquid seaweed. Trees have responded well to this operation, leaf size has improved, and deadwood formation has dropped.

belter

Thanks for the response treeshaveneeds, i did put the garden fork deep into the ground and tipped in the seaweed (seasol) all around the drip line i could get too. Maybe i should have a look at bigger cores. I had a arborist come out a couple of years ago and he pretty much said some of the northern hemisphere trees are getting found out due to the drought and suggested the mulching and watering. Add the coring etc. is it worth going down the injection/air spade or some other route? I really like the tree and its way cheaper to keep it alive than letting it die and costings a small fortune to remove. Thanks.

TreeSpecialist

Pictures?

The place to start - especially with pin oaks - is a soil test. They don't like the least bit of alkalinity.

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Eric Frei

There's some really intelligent and current advice here in this guys post.

Now putting garden forks, tines, spears etc is not the best. Also air injection in clay soils has been debunked too.

Read this thread, it is chock o' block with data and fact. To reduce compaction you need to increase volume, shoving things into compacted soil can increase compaction but drilling makes a hole, pulls the swarf (soil) up out of the hole increasing mass. Read this thread.

Soil Aeration Experiments| Grade Changes| Compaction| Decompaction

Here's a quote from post 29

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TreeSpecialist

Vertical mulching works well - takes a while to see results.

Using an Airspade® rather than a drill to make the holes seems to leave the soil more open.

In the 80's a german guy showed up in Texas with a Terralift® that supposedly fractured the soil and left it well aerated. The dozen or so trees he applied his machine to today look no better than when he started in 1986.

Making the soil a nice place to grow roots can start with a layer of compost ( 1-2 inches thick) followed by a layer of mulch. This should extend out at least to the drip line of the tree. Less labor intensive than vertical mulching.

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Eric Frei

Well, Terralift has been around a while then. Funny how things appear to return to their prior state of condition when left to their own. Natural forest are continually replenishing the forest floor with organic litter, the humus layer is continually being added and the microbes are reproducing happily. In suburbia, sure people have lawns around trees and in some tests lawn can exceed mulch for compaction benefits .... however, we mow the lawn (compaction), we fertilize it, we spray it with weed spray and we remove all the organic litter especially tree leaves and twigs etc.

There's some good shelf products these days to kick things along in the microbial dept, mulch & microbes (inc fungi) is the way forward for urban trees.

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belter

Thanks for the discussion guys, its winter here now so the tree has dropped its leaves there is not much to see in a pic but i can take one if you like. Under the drip line of the tree i have basically converted it into a horizontal compost heap where i throw all the excess leaves and mulch to rot down. I keep to about 7-10cm thick. I gather it takes a while to turn a big tree like this around from being stressed? The black saturday heat and earlier heat waves just cooked it in 2008-9 and it shedded a lot of the canopy mid summer.
As for a soil test, the next door neighbour has a pin oak that was planted the same time as mine (about 40-50 years ago) and theirs is thriving on neglect. Its about 20-30 metres away from my tree.
Realistically if the tree still looks like poo this spring/summer is it worth hiring another arborist or am i doing as much as i can for a foreign tree in harsh old oz?