Why is this tree's foliage yellow?

This is an older Atlas Cedar (I think over 40 years) in my collection. It hasn’t been repotted recently and it grows well as you can see (buds everywhere) but for some reason, its foliage is way off colour.

I can tell its original colour was what you get with a healthy Atlas Cedar because its older needles are a different colour (darker). So I checked to see if it’s infested with spider mites but nothing like that fell off it during my white paper test.

Does anyone know what might help this tree get its colour back?


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Excess of water might cause yellowing foliage evenly. Could that be the case?

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@CoffeeCherry ah interesting thought and that maybe, although it tends to be the same all year around even though in winter I hardly water it and winters are fairly dry here.

Whats the pH and alkalinity of the water and the soil? Maybe try to add some MgSO4 or Epsom salt? I water with the supplied city water which is aquafer fed and very “hard.” I use Epsom periodically to green up the plants. This acidifies soil and replaces magnesium and helps green up the foliage.
Just a thought.

Chlorosis perhaps? Giving the tree chelated iron could help get it green faster if that’s the case. Though I do think the root cause of cholorosis often has to do with watering or water ph being off or something, don’t quote me on any of that, but something to look into I would think.

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Whats the pH and alkalinity of the water and the soil?

I actually don’t know the answer to that question but it’s worth finding out. However, I wonder wouldn’t unsuitable PH levels in our water affect my other Cedars just the same way? None of the others trees has reacted this way - at least not yet.

Trees as a species have generalizable characteristics in terms of habitat preferences. Their ideal growth conditions and tolerances… pH, humidity, soil preferences, temperature, etc. But every tree is unique and individual in what it needs. I have through time found that all my plants periodically need MgSO4 supplementation. Most are annual to semi annual, however, I have an azalea that I frequently add Epsom salt to the soil bi-monthly. Its in pure kanuma and in theory should not have any problems with alkalinity and nutrient uptake, as kanuma is considered to be acidic. My other plants/azaleas do great with the regular but infrequent annual Epsom salt addition. I feel that when it comes down to maintaining the health of our bonsai it becomes an investigative process of elimination, we rule out problems until a solution is found. Pests, sun exposure issue, soil/water/root related problem, pot size and moisture retention, watering schedule, fungus, etc. There is sometimes no easy solution but if you elimiante enough problems sometimes the answer becomes apparent. For me the yellowing of my plants that are still growing tells me to add epsom salt after I have ruled out the rest.