Leaves discoloration on oaks started indoors

[sam_1421]

I'm asking here because I know you guys have extensive knowledge in starting trees indoors. I have been reading these forums for a while already and found the knowledge shared here very valuable.

I started many varieties of trees, mostly nut trees (oaks, hickories, walnut, horsechestnut) and followed a lot of the advice I read in this ver complete thread. Here are some information on my setup:

Containers: RootMaker 18 propagation trays (not the express individual ones, though)
Soil: Promix BX
Nutrients: Osmocote Plus mixed in
Light: LED grow lights (the ones weed growers use) in a 2x4 grow tent, synchronized with sunrise / sunset
Water: rainwater collected from the gutters, exclusively
Air: ~76-80 F, 45-60% humidity, fan one hour ON / one hour OFF
Sown 3-4 weeks ago

Here are pictures of the discoloration (those are english oaks but I also see it on other oaks):


The one on the left is an english oak I started a month before the others to test my setup. It's more evident on that one but the same pattern is starting to emerge on the new ones. Do you have any idea what it could be? It would be very unfortunate if I missed one small thing and it stunts or kills them.

Thank you!

 

[Teeder]

Welcome.
Most of my oaks look like that now under lights. Especially the English. They will harden up and get darker green once they're outside.
Caution, they need to be eased into the sunlight. Every year, I try to go easy, but get impatient and burn some.

 

[Johnrpb]

Probably an issue with the specific nm spectrum your led bulbs are producing. Weed growers use different spectrum bulbs depending on if they are wanting to promote vegetative growth or flowering/Budd growth. Check your bulbs to see was nm spectrum they produce and then adjust if too par on either end of the spectrum.
Couple of additional thoughts:
- you can run lights longer than natural sunrise/sunset now if you want to juice the growth while inside,
- 2nd what Teeder said, they are remarkably easy to sunburn when first taking outside, either severely limit the time at first or get some sort of filter net so they aren’t in full sunlight.

 

[sam_1421]

Thanks for the replies - it sounds like this is not a big issue then, especially since they're moving outside in maybe a month already.

- you can run lights longer than natural sunrise/sunset now if you want to juice the growth while inside,

Noted! I added an hour before sunrise and an hour after sunset, this will certainly help! I thought too it would promote more growth but I didn't want to do anything I was not sure was OK with these little babies.

I'll have a look at the spectrum, but they seem pretty complete already - I'm using 2x this. Maybe I can supplement with an additional bulb or two in specific wavelengths to promote vegetative growth as you said, it's a good idea.

Most of my oaks look like that now under lights. Especially the English. They will harden up and get darker green once they're outside.

Now that everything is growing a bit more, it definitely looks like this affects mostly oaks. I have horsechestnuts that are 3x the size of my oaks and some black cherry and they don't have any coloration issues.

It's interesting to experiment with this. We can get loads of information online about LED indoors growing but most resources we find are for weed growing. A lot of good advice but not everything applies, and their goals with the plants are different. There's definitely not a lot of info on starting trees indoors under LED lights and even less specific to oaks.

I'll keep looking around and experimenting on my own, and I'll report if I find something that works for oaks. I'm sure we can figure out how to get healthy looking plants even if they're not under normal outdoors lighting and conditions.

About the hardening, I definitely made mistakes in the past being impatient and set back some tomatoes and pepper plants because of this. How long do you recommend acclimating them before full midday sunlight exposure?

 

[yoderjac]

Nope, nothing to do with lights. Spectrum doesn't matter when starting trees indoors under lights. I've used cheap shop lights for years.

What we have here is Iron chlorosis most likely. It is most likely due to the water you are using. Most media, like promix, is pH adjusted to neutral. Chestnuts and some oaks want some acidity in the soil. Using rain water solves that problem as it is slights acidic. City water usually has salts in it that you want to avoid. Well water does not have salts if taken before a water softener, but it may not have the same pH as rain water. You can use some sulfur based products they sell for blueberries to adjust the pH.

You probably don't have an issue with iron itself. It is more likely the ability of the tree to uptake the iron because of the pH.

Thanks,

Jack

 

[sam_1421]

@yoderjac it sure looks very similar to iron chlorosis when I look at pictures and compare!

It's a bit strange though as I'm using rainwater already in a pH-adjusted to neutral mix, so if I understand correctly what you said, it should leave me with a slightly acid growing media, which would help prevent iron chlorosis). To get to the bottom of this, I tested the soil using a cheap yard test-kit I had. It's probably not the most accurate but should give an idea.

Two different trays gave me approximately the same result: between 6.5 and 7.0 pH. Soil from the single plant pictured above (which was planted individually in cheap peat-moss I had before the others) seems to have a pH closer to 5.5, however. It's a bit strange as Promix BX is 75-85% peat moss - I would have thought that given the same growing conditions, both growing media would have the same pH roughly.

So while 6.5-7.0 pH is slightly higher than oaks seem to prefer (and 5.5 should be perfectly fine), the iron chlorosis theory makes the most sense to me given the symptoms so far.

I had some Ferrous Sulfate Heptahydrate on hand and mixed some with water to spray the leaves of a few trays and plants. This should temporarily fix the iron chlorosis in a matter of a few days, from what I read. I'll be able to compare sprayed vs not sprayed and see if it really is iron chlorosis.

I'll report back in a few days with my findings. I'm probably going way overboard with this but I'm always looking to improve my technique, and I'm sure if plants could be even more healthy when started indoors it could help produce even better trees in the long run.

 

[Teeder]

My chinkapin and burr oaks have the same yellow and they aren't as sensitive to the lack of acid.
I've been starting oaks for over 25 years. City, rain, well, and well through a softener, I got the same results through the years.
Imo, you're over thinking it.
It could just be over-watering.

 

[yoderjac]

@yoderjac it sure looks very similar to iron chlorosis when I look at pictures and compare!

It's a bit strange though as I'm using rainwater already in a pH-adjusted to neutral mix, so if I understand correctly what you said, it should leave me with a slightly acid growing media, which would help prevent iron chlorosis). To get to the bottom of this, I tested the soil using a cheap yard test-kit I had. It's probably not the most accurate but should give an idea.

Two different trays gave me approximately the same result: between 6.5 and 7.0 pH. Soil from the single plant pictured above (which was planted individually in cheap peat-moss I had before the others) seems to have a pH closer to 5.5, however. It's a bit strange as Promix BX is 75-85% peat moss - I would have thought that given the same growing conditions, both growing media would have the same pH roughly.

So while 6.5-7.0 pH is slightly higher than oaks seem to prefer (and 5.5 should be perfectly fine), the iron chlorosis theory makes the most sense to me given the symptoms so far.

I had some Ferrous Sulfate Heptahydrate on hand and mixed some with water to spray the leaves of a few trays and plants. This should temporarily fix the iron chlorosis in a matter of a few days, from what I read. I'll be able to compare sprayed vs not sprayed and see if it really is iron chlorosis.

I'll report back in a few days with my findings. I'm probably going way overboard with this but I'm always looking to improve my technique, and I'm sure if plants could be even more healthy when started indoors it could help produce even better trees in the long run.

Best of luck! As I said, it is usually an issue of the trees ability to uptake iron rather than a lack of iron in the media, but it couldn't hurt to add some micromax.