Hi Bonsai-en, I purchased a Juniper bonsai tree in November 2019, I believe it is around 7 years old and was in very good health at the time of purchase, however I’ve since seen it become more yellow/light green over time. As someone who is very new to bonsai I have tried to correct some initial mistakes such as over-watering, placement and feeding, however as much as I’ve tried to correct my mistakes, the yellowing is looks to be getting worse.
I received a care guide with my tree; it was very explicit regarding watering “WATER YOUR TREE EVERYDAY” it said, and I done this for 2–3 weeks before I started noticing slight yellowing. After contacting the nursery and doing some further research I have reduced watering to when the soil is almost dry, I say almost dry as I wait till the surface is dry but still has a bit of moisture an inch deep, I still try not to let it get bone dry so watering occurs roughly every 2-3 days.
Initially I had the bonsai in an area that received about 4 - 5 hours of direct sunlight with shade. After about 6 weeks the yellowing started to get a bit worse so I moved the tree into an open area, it gets full sunlight but we have a high fence so not too much wind.
I received my tree with a small bag of slow release fertilizer which I was instructed to place around the tree. About 4 weeks ago I took my tree to a bonsai meet up, as the yellowing was starting to progress. One tip I received was to try a bit of liquid fertilizer once monthly to see if this would help. I purchased an all purpose liquid fertilizer N.P.K 9.4.5. At this point I didn’t want to overfeed so I gave the tree half the recommended dose, which was 2.5ml per litre, this I did about 2-3 weeks ago. At the time there was only 1 small branch that was really yellow, so I removed this branch; however more branches are now yellowing. I had intended to add the liquid fertilizer once monthly but at this point I’m unsure if to increase or decrease feeding.
I really hope I can save my tree, I’ve been reading up on possible solutions including testing the PH of the soil and treatment for iron deficiency and maybe even reducing watering a bit more, However at writing this we are at a level 4 lockdown here in New Zealand due to Covid-19, so all stores are closed and I am unable to purchase anything. I’ve attached some dated photos so you can see the progressive yellowing that is occurring.