Boxwood Leaf

This leaf came from Buxus Microphylla 'Faulkner' and I'm wondering if anyone can offer some input as to what's going on here. I just came into posession of this tree and this is happening to the foliage in various places, but not all. Any help is appreciated.

Jesse

See this post it may help.
https://ibonsaiclub.forumotion.com/t8618-warning-be-on-the-lookout-for-this

Thanks, Bob. Forwarned is forearmed, after all...

I guess the good news is that after a visual inspection I could find no evidence of spore clusters, black places, or dead ends. The tree has been pruned back though, which would of course have removed the latter evidence. All I can figure for certain is that whatever is causing the leaves to wind up with that funky center stripe affects all the leaves the same. There are a few dead clusters of brown leaves, but again no spores that I can detect. The leaves are either healthy looking and green or they have that funky brown center patch. Likely I'll take it in to the Ag agent soon and see what they can tell me.

Here's hoping the blight leaves all our gardens alone.
Jesse

Let us know what the ag office says.

And in the meantime keep it well away from any other boxwoods in your collection or on your property, and sterilize all tools that may come in contact with it.

So the tree was returned, but not before I took it by the Ag office and left a sample branch with the master gardener there since the agent was out today. They should be getting back to me as soon as they know anything. Fingers crossed...

That leaf doesn't look happy, but you do know that Buxus mycrophylla leaves have a major leaf color change (orange-yellow-brown) during cold weather, and get pretty ugly. Other boxwoods may also, I suppose.

Question for the OP (Jesse) - in the posted image, the bulk of the leaf looks almost black, except for that center stripe. Is that just from the lighting? Is the outside part of the leaf actually green? When I downloaded and manipulated your image, I got this - which makes the outer part of the leaf look green (i.e. "normal"):



Checked on my one little boxwood that is in a bonsai pot, and I have a somewhat similar discoloration. The plant was allowed to be exposed to cold weather in the fall (to just below freezing) and has since been in protected storage, temps between 30-40 F. Here is a shot of some of the leaves:



I've been assuming this is a "normal" winter coloration, but cannot recall if the leaves looked like this last winter. Not all the leaves are showing this discoloration, some are still all green. My concern is that I may have let the tree get too dry this fall/early winter. I've got a couple of other boxwoods in nursery containers that have become very brown/yellow, quite ugly - but again, I think it's normal. They're out in the barn so I'll look more carefully at the leaves tomorrow.

Anyone else with boxwood in cold climates - what do your leaves look like?

Chris
I believe your boxwood leaves are displaying pigmentation changes based on cold exposure, and is probably normal for your Box. The image Jesse posted shows necrosis of the leaf cuticle even down into the upper epidermis and mesophyll layers, this is evidenced particularly by noticing that on your healthy boxwood leaf the midrib, though discolored, is still very noticeable, raised, fleshy and healthy. The same midrib on Jesse's leaf is clearly sunken and diseased and almost completely unnoticeable. You can see the boundary where the cuticle looks "eaten away" and your photo enhancement actually helps bring out the dark banding that highlights that boundary.

My big Boxwood (microphylla koreana) is in storage at about 36F and gets nice sunlight. It displays a range from sulfery yellow, some ruddy reds (kinda like yours) through pale green and even some darker green leaves. Reds and Purples in winter are often common color changes evergreens display in response to cold, Azaleas being very notable for the purple effect of winter on their leaves.

Discoloration or not yours certainly looks healthy with all those small extending buds I can see in your photo just frozen in time waiting for better days!
-Jay

Thanks for your thoughts, Jay. I do see the "pitting" in Jesse's leaf that is not present on my tree. The dark band along the edge of that discolored area is also different. Hopefully we'll get some kind of determination as to what's going on with that tree.

My boxwood is in a location that gets very little light during the winter. I'm sure that plays a role in the coloration.

Yeah, those partially extended shoots are strange. Last year it all the summer growth matured before fall, this year it kept going well into the fall, with many shoots not maturing before winter set in. Hopefully it'll pick up where it left off in the spring.

Chris

I've been surprised how much water my Boxwood has gone through so far this winter, this year its in a slightly warmer spot than last year and my leaves have remained fairly green, growth never really stopped this year it just slowed to a crawl. last year it spent the winter in my unheated green house and turned a very sickly yellow. But then bounced right back to normal in spring. Bloomed profusely in late March, it hummed with hundreds of my bees all over it enjoying their first taste of spring.
-Jay

Anyone else with boxwood in cold climates - what do your leaves look like?

Exactly like yours. My boxwood stays outside all winter. So far this year, temps have dropped to 18-19 F but it has been much colder in past years.

Jim, thanks for that info!

Jay, it's really been a strange "winter". I've had a tough time getting it cold enough in one of my storage areas (unheated mud room, where the boxwood is). All these days in the 40s and even 50s and extreme temperature swings (from 0 to almost 50 in less than 48 hours) are creating chaos!

So I finally heard back from one of the master gardeners in our local office after he had a confer with the Ag agent. He said that the best guess they could come up with was either leaf miners or drought. Either way, the plant is no longer on my grounds and I am much relieved. Now it's time for a cold beer...cheers, folks!

Could possibly have been leaf miners, I didn't see any blistering to the leaf that usually accompanies their presence. I doubt it was drought. Well seeing as miners overwinter in boxwood and return the next year, if thats what the cause was your better off without them!
Job well done! enjoy your beer.
-Jay