Yellowing Shimpaku

Help please? This happened last year around this time. Yellowing of the foliage nearest the branch ( some at tip but more at the branch side ) spreading ( last year) through the tree. My local bonsai folks thought maybe Juniper tip blightor other fungal problem ( lord knows we have every fungal disease here in the PNW) and recommended Fungoil. After removing all the yellow and 2 applications it stopped. But not sure if the oil was it. It seems worse than just senescence. This year I prophylactically treated w/ copper. But here it is again. Anyone know what it is? I am watering thoughtfully, percolation is good, checked for beasties so I think its fungal?


Have you checked for spider mites?

Garret - Thank you. Yes. While I saw them in a couple of other trees ( deciduous), I got on that FAST. I never found any on this tree

How frequently are you watering? Does the soil dry out a little between waterings? It’s hard to tell from a photo but my best guess is that this is an overwatering situation. You might try backing off on the water and protecting from rain if it isn’t time to water. You also might prop one side of the pot up on something so that the pot is at an angle. This creates more downward force and helps the water move through it better. It can however create a pool inside the pot so you might need to drill a little hole in the bottom of the pot. Use a ceramic bit and a squert bottle of water to keep the pot wet and go slowly.

1 Like

Thanks Jenn. I think you are right. While I repotted, the remaining roots and soil were pretty compared and I think don’t get to dry out enough. So I am going to try to err on the dry side ( at least at the center ) and see if that works.

I agree with Jenn. Probably not fungal. Most times when the problem is all over the tree and effecting the foliage at the base of clusters, it indicates an issue with the roots. When a juniper is having problems, the foliage should only be removed when it is brown.

You said you repotted. Did your problems occur after the repot? Your new soil may be holding more water. If that is the case, you may want to consider a larger particle size next time. A new pot with smaller drain holes or no feet can do the same thing = Less oxygen coming from the bottom. I like to set up my pot and particle size so I can water once a day because when you water, as the water drops though the soil, it also draws fresh air into the soil.

Since you say it is only happening in the summer, it could also be under developed roots (after repot). In that case, less to no fertilizer and just maintain and do not prune foliage until healthy.

Good luck with your juniper, and have fun.

1 Like

Almost positive now it is over watering combined with drainage issues. Problems predated the repot. I repotted into same pot with good drainage. And while the new soil is drying out ok , the remaining soil - really broken down and compacted, less so. So I am checking that soil more carefully and am shocked at how slowly it is drying out. I didn’t want to remove too much of the root mass on the repot - I removed about 50%. And the problem is absolutely at the base of the clusters. Everything I read about fungal problems w/ junipers was at the tips so the root issue is more logical. Next question is - should I repot again next year and try to remove more of the old soil?

No, a repot would be bad. Let the roots balance out. All the signs, especially the 50% root reduction, are pointing to underdeveloped roots. junipers shed their interior foliage when they are stressed. This is not a bad problem. Let it grow, prune as little as possible and keep it out of the hottest sun of the day. I have one that is doing the same thing from frost kill of the roots.

Good luck

Thanks for the help, folks

A bonsai noob here, reopening the chamber of yellowing Shimpaku foliage.

I attached some pictures of a couple trees with what I believe is a similar condition to what was discussed earlier in this thread. My gut (and awareness of my over-nurturing personality) says it could be the same over-watering issue. I do check for spider mites and other pests regularly, and have been adhering to a regular treatment of Neem + Bronner’s baby soap + rubbing alcohol diluted with water. Perhaps that could be an issue?

After reducing the amount of waterings and paying closer attention to the moisture in the remaining potting soil from the first repot, and after ensuring good air flow in the bottom of the pots, what kind of timeline might I expect with regards to improvement? Will I lose all of the yellowed foliage, or will some green back up?