Dawn Redwood Leaves Curling

njohns321

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Hello everyone, I am having issues with my dawn redwoods. The leaves are all curled. I am keeping them well-watered, but I'm thinking it may be the heat and sun. I just would like confirmation on that or if you think it's something else. I fertilize once every two weeks and water mostly with RO water and some tap. I also am wondering if I should just keep them in the shade. Right now they get about 3-4 hours of very bright, direct sunlight. I am in Montana, and the sunlight here is very intense in the summer with little humidity. It's been in the high 90s-100s for the past week.
 

njohns321

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Alright here you go:
 

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Brad in GR

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In my experience this is absolutely related to stress from heat. I had this on most of my dawns in 2019.
Do you have your dawns in “bonsai” substrate, or something more organic?
Zone 6a here, I have found that Dawn can handle our occasional days in the 90’s if they are in a soil with at least 50% organic. @Forsoothe! has opined in the past on this as well, and he is absolutely correct.
I believe he prefers 100% organic, in fact.
With an organic mix (or sure, 100%) they can handle the heat. If they are in pure ‘bonsai’ inorganic soil I find that they struggle on the very hot days.

a stopgap in my experience (trees that I am not ready to repot, but potted into mostly bonsai soil when I was more foolish on the topic a few years ago) is the submerge the container in water on very hot days.

cheers.
 

njohns321

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Thank you, and by organic you mean organic matter, right? I make my own soil, and I'd say it's like 20-30% OM. I have a lot of them, and I don't want to lose them. I am running a nursery, and it will be a huge loss if I do. It's just been so insane here; I've lived in MT most of my life and have never seen temperatures like this. I'll repot all of them if need be, but I just want to make sure first that that's what's going on.
 

Wulfskaar

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If the problem is the heat and lack of water due to fast draining soil, why not try to put mulch on top of the soil? Isn't that supposed to help retain water by limiting evaporation?

If the heat wave is temporary 🙏 then something like that might be easier than repotting everything.
 

Cadillactaste

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If the problem is the heat and lack of water due to fast draining soil, why not try to put mulch on top of the soil? Isn't that supposed to help retain water by limiting evaporation?

If the heat wave is temporary 🙏 then something like that might be easier than repotting everything.
I wouldn't do mulch. I would worry itnheld onto the moisture longer than the substrate below it. I use New Zealand spaghnum moss for top dressing. As many in bonsai do.
 
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I cultivate then the same as bald cypress, try submerging them in water at the 50 % line of your container.
 

Wulfskaar

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I wouldn't do mulch. I would worry itnheld onto the moisture longer than the substrate below it. I use New Zealand spaghnum moss for top dressing. As many in bonsai do.
Thanks for that. Would you recommend the sphagnum moss for this particular issue?
 

Brad in GR

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Shade also won’t kill these trees, so if the wave is temporary then that is an option. I would not risk repotting in the middle of summer personally…
 

Vance Wood

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I would go for the shade and, if not changing the soil mix to a more organic one, I would place a good amount of peat moss on the surface as an insulating layer as suggested.
 

Forsoothe!

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I don't think I'm looking at drought. Pick a disease or pest. Level of ferts may be problematic, exactly what are they?
 

sorce

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The extra heat probably made them susceptible to mites.

Welcome to Crazy!

Sorce
 

hinmo24t

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they love water and they dont love direct sun

semi sun


some ppl put them in tray of water or drainless pan.
i had mine like that and wasnt blown away so i removed water tray
and she is fluffing out nice now, but i keep it wet and use a straw mulch to keep it moist.
just dont have your mulch touching the trunk to encourage rot.
 

Forsoothe!

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Mine is in the most sun I have, all day, maybe 12 hours. No problemo in organic soil. Assuming "bonsai mix" is appropriate for every species on Earth is probably a dumb conclusion. Maybe it's not really a conclusion, a word which insinuates a thought process considering more than one option.
 

LittleDingus

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I agree with "insect" over "heat" damage. I've never seen redwood leaves curl like that due to heat. The tend to shrivel and turn dull.

20210702_112854.jpg

My heat is typically a humid heat. I suspect yours is not...which I would think would lead even further from leaf curl due.

I have a couple that are in full sun dawn time 5PMish. This one, for example:

20210702_112918.jpg

It will lose some tender new growth from time to time due to the heat if I don't mist it during the hottest part of the day...but it takes my full sun well enough.

That said, I'm at 900' above sea level. Full some here comes with mid 90F days at high humidities. Depending on where in Montana, you have a mile less atmosphere...and a LOT less humid atmosphere...than I have to contend with!

I still don't feel the sun/heat is curling those leaves...but shade/mist/water are still likely warranted.
 

njohns321

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Ok, thank you all so much for your input. I really am at a loss.

I am going to try to repot a few with more OM, move some to the shade, and yeah I can try misting too.

Yeah my elevation is like 3,000'. I'm learning that "full sun" doesn't mean full sun in Montana. The sun is just really intense here. Back east it's pretty hazy, which diffuses the sunlight.
 

LittleDingus

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Ok, thank you all so much for your input. I really am at a loss.

I am going to try to repot a few with more OM, move some to the shade, and yeah I can try misting too.

Yeah my elevation is like 3,000'. I'm learning that "full sun" doesn't mean full sun in Montana. The sun is just really intense here. Back east it's pretty hazy, which diffuses the sunlight.

I also do astronomy. I've got nice data laying around somewhere showing the effects of atmospheric extinction through different elevations (the data is actually angle through the atmosphere but equates to elevation) I've got some data on extinction through different humidity as well. It's pretty impressive!

I have no doubt that at your low humidities and higher elevations that "full sun" means something like 2x the photons "full sun" means to me here! Protection is definitely warranted.
 

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