Chinese Elm has brown spots

[Wulfskaar]

Hi B-Nutters!

I've been growing a Chinese Elm from seed and it's been doing well, for the most part.

However, it is getting some brown spots on it. I could not find anything with the exact same spots.

My first guess is that it's fungal, but I have seen other posts about too much water. But in the "too much water" posts, the brown spots looked different and larger.

Any ideas?

 

[Bonsai Nut]

I've been growing a Chinese Elm from seed and it's been doing well, for the most part.

Good for you on the "growing from seed" part!

Having grown tons of Chinese elm in SoCal, I don't recall ever seeing those little spots. It would be a strange time for fungus - late fall in SoCal. Almost looks like pinpoint insect damage. However I see yellowing around the leaf fringe and wonder... is this just the tree getting ready to drop leaves?

 

[Wulfskaar]

I've got some copper fungicide handy. Would it hurt to give it a nice bath before bedtime?

 

[Wulfskaar]

Hmmm... the only similar pics I see online (on plants other than elm) are supposedly from fertilizer burn. I do fertilize with liquid every 2-3 weeks, so maybe I used too much?

 

[Bonsai Nut]

Hmmm... the only similar pics I see online (on plants other than elm) are supposedly from fertilizer burn. I do fertilize with liquid every 2-3 weeks, so maybe I used too much?

Fertilizer burn is universal... in other words it does't show up as dots, but entire leaves crisping then dying. Fertilizer burn is actually a misnomer. It should be called "root burn" from over application of fertilizer. Roots get burned, they die, and the associated foliage dies. It definitely doesn't show up as small dots on leaves.

 

[jeremy_norbury]

Looks fungal.

I'd defoliate it of all the affected leaves. I had something MUCH worse on some wych elms from seed this year and complete defoliation saved the day here.

 

[Wulfskaar]

Fertilizer burn is universal... in other words it does't show up as dots, but entire leaves crisping then dying. Fertilizer burn is actually a misnomer. It should be called "root burn" from over application of fertilizer. Roots get burned, they die, and the associated foliage dies. It definitely doesn't show up as small dots on leaves.

Yeah there is so much conflicting info out there. I'm glad to hear from people with real experience.

Looks fungal.

I'd defoliate it of all the affected leaves. I had something MUCH worse on some wych elms from seed this year and complete defoliation saved the day here.

That terrifies me.

 

[jeremy_norbury]

This is how mine looked earlier this year

IMG_7506 by Jerry Norbury, on Flickr

So I pruned off ALL the foliage - nearly all branches removed.

IMG_8001 by Jerry Norbury, on Flickr

And they grew back without the issue

IMG_8960 by Jerry Norbury, on Flickr

 

[63pmp]

I think overwatering as well. Needs a repot. Black dots are related to manganese toxicity which becomes more available with waterlogging; not a fungus.

 

[Bnana]

The example of jeremy_norbury looks different to me, that looks like some pest, probably fungal.
The original photo does not look fungal to me, the pale edges of the leaves indicate a nutrient issue and the brown spots are not raised or deformed.
What soil do you have? how do you fertilize? 6pmp might be right.

 

[Wulfskaar]

Hi @63pmp and @Bnana,

What you guys are saying is more in line with what I found googling this. The pictures I found that most closely matched had commenters saying it was either too much water or "nutrient" (fertilizer) burn, but those were on a different plant altogether. I could not find pictures of chinese elm with this pattern of brown dots.

I grew it in straight peat. I plan to repot into better soil and pot in spring.

It gets fertilized with 3-3-3 liquid every 2-3 weeks. I wonder if I used too much on such a small seedling. It also gets plenty of water, so it's possible I am watering too much. I'm still also open to the idea of it being fungal, but am worried about defoliating because it's still growing.

 

[Bnana]

Peat is a horrible substrate. It's very likely the roots are too wet (the actual problem being not enough oxygen). Reduce watering but don't let it dry completely.

 

[Wulfskaar]

Peat is a horrible substrate. It's very likely the roots are too wet (the actual problem being not enough oxygen). Reduce watering but don't let it dry completely.

Ok. Will try that first. If it gets worse, I'll go ahead and defoliate in late fall.

Would it hurt to use some copper fungicide just to be certain?

 

[Bnana]

It's toxic to mycorrhizal fungi. Those already have a hard time as they need oxygen in the soil. So I wouldn't use copper on a plant like this.

 

[Wulfskaar]

In more tropical parts of Australia where they don't actually have winter the Chinese elms never lose leaves and are always growing. They still grow and repot Chinese elm. They have discovered that Chinese elm can be root pruned and repotted any time of years without harming the tree so don't be concerned about missing the traditional repotting time for Chinese elms.

@Shibui I copied a comment you made a while back in another thread (https://www.bonsainut.com/threads/repotting-chinese-elm.42233/)

I'm in a Mediterranean-type of environment (southern California). We have "winter" but it's very mild. We might get below freezing once ever 10 or 15 years (guess). Average high in January is 62 F.

My Chinese Elm (6 months old) has brown spots, most guess due to over-watering. It's in the peat that it was germinated in. The leaves have not changed color yet and there are a couple new leaves growing in. Unlike the thread where I copied your comment from, mine is not budding at all, just growing longer on it's very long and skinny main trunk.

a) I feel it needs a repot into good soil. Is your comment above true for a non-tropical environment?
b) Should I remove the leaves in the case that the spots are a fungus?
c) If a, then no b?

 

[Shibui]

A long, skinny main trunk with few side shoots is quite normal. Like many trees they are adapted to try to grow to the top quicker than any competitors so putting all your resources into tip growth makes a lot of sense. To get side branching you need to take charge. Pruning will activate dormant buds just below the chop site. Fortunately Chinese elm are really good at making new buds after a chop so it generally does not matter how big or how old the trunk is. New shoots will develop after pruning. Chinese elm will even develop a ring of buds from exposed cambium around the circumference of a trunk chop so it does not really matter if your seedling does grow tall. It will be easy enough to reduce height when you need to.

You should be able to repot most trees pretty much any time of year provided you don't root prune heavily. I repot seedlings of all species whenever they need it - right through summer and into Autumn, even if that does require root pruning. A 6 month seedling is still in that very young stage where they can recover from almost anything.
Fall repotting (with root pruning) should be safe provided you still have a few weeks of growth before leaf drop (if they do drop leaves there) so the tree can start to heal the cut roots.
I have had some bad reactions to heavy root pruning when I dig advanced Chinese elms from the grow beds early in winter. They seem to get infection in the cut roots while it is cold and wet so I now dig those later in winter or closer to starting new growth which for Chinese elm is any time from mid winter through to spring.
Having only experienced this one growing environment I can't say what temps or winter conditions would be the change point from late winter safe to all year round safe. Having had the experiences here I would probably advise erring on the side of caution and doing any root pruning in warmer weather rather than colder. Even though we do get below freezing nights through winter Chinese elm seem to be on the borderline of evergreen. Trees in the grow beds frequently retain leaves and continue to grow through winter. My guess is yours will probably retain leaves most years and may even grow all year there.

I can see I have been hedging my bets rather than giving you black and white answers but that's because there are no definitive answers.
I would certainly be happy to repot a 6 month old seedling (with care) any time of year.
Removing infected leaves is always a good idea as that should reduce spread to new leaves. Your tree may or may not grow new leaves this late in your season but if it decides not to shoot, having no leaves through winter should not hurt it.

 

[Wulfskaar]

A long, skinny main trunk...

Thank you @Shibui ! You always give a lot of clear and good advice on here and I appreciate it very much!

I think I may go ahead with a repot just to get it into better soil, but not mess around with the roots until another time.

 

[Wulfskaar]

UPDATE: I just noticed it's starting to back bud way down the trunk. We're in our second warm spell already this fall, so that must be what jump started it.

 

[Wulfskaar]

More buds are starting to swell and extend all the way up and down the trunk, so I may be repotting very soon.

 

[Wulfskaar]

I went ahead with the repot into good quality soil. While the season is off, the swelling/elongating buds told me it was time. Hopefully it isn't too shocked, as I did not prune any roots.