I have a row of Elaeocarpus Eumundi along my back fence of my Sydney property that are over 10 years old and mostly doing well. There is one tree that is not, for some time it has been looking paler and a bit more scraggly that the other trees. I had not being doing much special care to these trees for a while since they were quite established. In January this year I noticed that the problem tree was quite dry around the base so I watered, mulched and added some enriched cow manure. I kept up water to the tree but my March it still wasn’t looking any better.
The leaves are a pale colour, and they are spotted with what looks to be a nutrient deficiency. Day by day the leave continue to drop to the point that the tree will have no leaves within a few months. There are signs that new growth wants to come out, but it never seems to happen. The last very small flourish of leaves came out quite pale with green veins but light green leaf colour otherwise. Everything that I read suggests that the tree is suffering a nutrient deficiency, or potentially too much phosphorus. The soil is relatively high pH (6.5 – 7). A tree arborist suggested to try and adjust the soil PH down which I started trying around 5 weeks ago. I tried sulfur powder, and then a few weeks later liquid sulphur (since the powder didn’t seem like it was getting absorbed). In between I also tried Iron Chelates since I read that may help with getting some green back into the leaves in the short term. We have had quite a bring of rain in the last few months. Nothing seems to be making any difference and I worried that the tree will die. Would appreciate any thoughts on the matter.
Well it is most definitely undernourished e.g. it is struggling along but is lacking everything it needs to be vital and healthy. But the big issue here is that the others have not been reported by you as being poorly in any way. If you have soil structure issues or ph problems or anything else then it would definitely affect all the plants in that area. It is possible to have a small pocket of different soil structure but this is not common. Winter is not a good time to be monitoring and applying remedies as the growth rates will be quite reduced. But in springtime it should be starting to burst back to life - if it doesn't then I'd suggest a strong burst of nitrogen, this is what makes the leaves green which in turn produces the energy by photosynthesis from the sun. Urea is a good source, so is Sulphate of Ammonia which also delivers sulphur too. Don't overfeed but applying a good dose in late winter may give you a decent chance. If not then there's something hidden like underground bugs eating the fine feeder roots - but we can only guess at that. As with all these conundrums it is best to speak to a local specialist, like an arborist who can see the local conditions, ask questions and even test the soil for you.