Shrub Detective needed! (Boxwood Health diagnosis) - THANK YOU!

[dklecko]

Hoping there is problem we can solve:

Background:

- In the PNW (USA)
- 25 Green Gen Boxwood (Buxus microphylla var. koreana x Buxus sempervirens) in 9" diameter containers on a deck (S side of a residential building)
- plants get full afternoon sun, summer temps in the 90s and fall temps high 30s to low 40s
- planted April 2020
- pruned May 2022 (normal healthy growth to this point)
- fertilized June 2022 (10-10-10)
- plants checked daily for soil moisture

As of June, 2022, leaf tips began to show yellowing (just the tips, body of leaf healthy green). This is abnormal for this cultivar.
As of October, 2022, plant leaves also began to show moderate bronzing

I suspect the leaf tip and bronzing may be due to a mineral deficiency and/or possibly the soil being too acidic (have used pine mulch around the plants)

Thoughts on factors contributing to lack of plant health? Thanks!

 

[dklecko]

Attached are photos of the plants

 

[Oliver Buckle]

They are not huge containers for the plant size.
Lack of iron can make the leaf tips yellow, but box is pretty unfussy about nutrients, my cuttings have been in trays that got flooded by rain in a way that would wash out most nutrients, and don't care. The only thing I have had to watch is watering, if the bottom of the pot is wet or damp they are okay, but I have lost a few to dryness. I grow a variegated one, but yes, they do get yellow if too dry.
Don't know what the pine mulch would do, it is well acidic, blueberry loves it.

 

[dklecko]

Thank you Oliver!

• I have a concern for container size too, given the size of the plants (drip line is nearly the edge of the container), point well taken.
• As to iron, I suspected that too.
• I will closely heed your advice on watering (while late autumn, being on a wind swept deck I think has caused the plants to dry out more than normal). I mentioned pine bark as I have read boxwood appreciates nearly neutral pH soil; the bark may have made soil more acidic and may possibly contribute to plant discoloration. Am I mad to think that?

Thanks, Dave (Seattle)

 

[DirtMechanic]

Thank you Oliver!

• I have a concern for container size too, given the size of the plants (drip line is nearly the edge of the container), point well taken.
• As to iron, I suspected that too.
• I will closely heed your advice on watering (while late autumn, being on a wind swept deck I think has caused the plants to dry out more than normal). I mentioned pine bark as I have read boxwood appreciates nearly neutral pH soil; the bark may have made soil more acidic and may possibly contribute to plant discoloration. Am I mad to think that?

Thanks, Dave (Seattle)

Mine grow in 5-5.5ph drained clay. I have read about magnesium toxicity (iron) and winter damage capable of making these symptoms. Hard to guess. What do you fertilize with? Slow release organic?

This was interesting,:

My boxwoods have a yellow leaf edge. Deficiency?

Boxwoods planted last spring in a shallow trench now have a distinct yellow leaf border. Wondering if this is a nutrient deficiency? Or symptom of...

forums.botanicalgarden.ubc.ca

 

[kasigarden]

Thank you