Cotyledons are turning light green to yellow...HELP

I, too, am new to growing from seed; however I currently have several flats, about 6, that have germinated. Most are in peat pellets and were planted in a seed tray with a clear lid. When they sprouted, I removed the lid and placed the seedlings under lights, with the lights about 3 to 4 inches above the seedlings. I have been misting the seedlings twice a day with a diluted 3 % H2O2 and water solution. I also keep the lights on about 14 to 16 hours daily. (All of this I learned from this forum by the way!) I noticed tonight that the larger seedlings' (which are about 2 to 4 inches tall) cotyledons are turning yellow.

Could they be getting too much light or too much H2O2? Should I be watering with 100 % water at least once daily rather than the H2O2 solution twice daily? Is it beceause the 1st true leaves may be getting ready to show and the cotyledons are dying?

Any information anyone could provide would be greatly appreciated. I have truly enjoyed growing my little seedlings and I would like to make sure they live.

Do these seedlings have true leaves yet?
The cotyledons will naturally turn yellow and shrivel and/or fall off when the plant can photosynthesize.

No, no true leaves yet. It is primarily my hollyhock seedlings that are doing this.

I would stop using the hydrogen peroxide so much, its not necessary. I would also stop misting the seedlings, and start to just water as needed. You should only mist when the seeds are germinating, and then after they have germinated, switch to watering. I would also let the soil dry out some between waterings and you will get better roots. You will be surprised at how well seedlings do in dryer soil.
If the seedlings are 2-4" high, you should see some true leaves-thats a tall seedling to not have any true leaves. I would start to fertilize with a very mild solution of fertilizer once a week after they start to put out their true leaves as well.

When you say a mild solution of fertilizer, how much is that. The Miracle grow I have says 2 teaspoons per gallon if inside. 1 T. if outside. But I don't know how much to cut it .

I think that 1T /gallon is about 250-300 ppm ( I think, I don't fertilize in that small amts, so not sure, but I think that I calculated the ppm (parts per million) for someone once. So you would want about 50-75 ppm, which is just under a teaspoon /gallon.

This is in general, depending on the numbers on the fert

I agree... time to switch from misting to bottom watering. The yellow could be from too much moisture.

I use half strength or even quarter strength Miracle Gro on seedlings, and they don't even get it every time I water. If they get too much nitrogen, you could get a lot of top growth without a corresponding amount of root growth... If top growth seems to stall after potting up, don't worry, the seedlings are probably just putting their energy into growing roots.

I have transplanted some of my seedlings already. The first set I sprayed with "deodorized" fish emulsion. Unfortunately, you can smell it in a small enclosed room, and the smell lingers. Even worse, it attracted my cat's attention. We are now working on some urinary problems. Cat urine is probably one of the nastiest things on the face of the earth, but we are coping with lots of ammonia and natural enzymes.

At any rate, I am now looking for a subsitute for the fish emulsion. I would like to use something organic. The organic fertilizers that I know aren't available immediately to the plants, but breakdown over a few months. I would welcome any non smelly suggestions.

I use fish emulsion exclusively, and I just plan for 1-3 days of stink. The seedling area gets quarantined until the smell dissipates so that the whole house doesn't share in the olfactory wealth ; ) . However, I do not have cats to deal with. Only water dogs who LOVE the smell, and have some serious, um, *consequences* if they get to it, haha.
Is Osmocote not organic? Forgive my ignorance on this subject. I only use fish emulsion or compost, so I'm not familiar with the other options/techniques.
I don't fertilize until the cotyledons have fallen off, and even then about every other week, at most.

I think that Osmocote is supposed to be organic, but I also believe that it takes some time to break down and be available to the plants.

I could be wrong, but I really don't think Osmocote is organic. It's a synthetic controlled release fertilizer.

But is synthetic inherently bad? Is it toxic to wildlife? I've never really looked into it. Would it be bad to use Osmocote in a greenhouse, say, where runoff is minimal?

I like Osmocote, myself, but I understand that with any synthetic fertilizer, salts can build up in the soil or potting mix over time, and that can be detrimental to your plants... that's not generally a problem with compost and other organic sources of nutrients.

So, that still brings me back to my question of what else I can use for the seedlings? I don't think that compost is a good option for them now. I would like to find something that doesn't have a scent since this is an enclosed environment.

I don't think that synthetic is bad necessarily, but I am trying to use products that will enrich the soil over time. From everything that I have read, it makes sense to feed the soil, which will feed the plants in return.

Feeding and enriching the soil is more relevant if you're growing things in the garden. In a container with all the moisture and temperature fluctuations I don't think you're ever going to get a good population of microbes, etc. Plus potting mix needs to be replaced frequently--your garden soil is always there and doesn't get changed out so it makes sense to try and improve it. Also compost and other things that are great for your garden tend to collapse as they decompose and that can create drainage problems in containers. I'm strictly organic when I'm dealing with the garden beds, but for containers I don't worry about it nearly as much, I'll use synthetic fertilizers, etc.

I know nothing about the difference between organic and synthetic, but I use 1/2 teaspoon Miracle grow to a gallon of water for my seedlings. I try to wait until everybody has their first set of true leaves, but in some cases (since I have up to 9 diff. varieties of seedlings per flat) they don't all grow at the same rate, so some get fertilized a hair earlier. I've heard wonderful things about fish emulsion, which I plan to use soon, but I haven't used it yet, so I guess I'm in for a real surprise when I smell it! Luckily my greenhouses are outside!!

Feeding seedlings is not actually necessary. The cotyledons contain plenty of nutrients to last for several weeks. I never fertilize until about 6 weeks old. Then it's about 1/4 strength Miracle Gro for veggies. (it has a lower N content) They get that one time before setting out into the garden...that's it.

Sounds like the yellow cotyledons are from excess moisture. Let them dry up some. As stated above by several others, excess moisture causes all sorts of problems, and is one of the most common issues with seedlings. I water as little as possible, always from the bottom and never mist seedlings at all. I keep a small fan blowing on them lightly to keep the leaves as dry as possible, and it strengthens the stems at the same time. It's not too much light. They need every bit that they are getting.

I've decided to try kelp. Fish emulsion works wonderfully - OUTSIDE!

Gosh Melody, I think that I would respectfully disagree with you about not feeding seedlings. They are actively growing and even though I don't use full strength fert on them, I notice a distinct nutritional deficiency with them if they get bypassed on the fert schedule. Certain plants are heavier feeders than others,granted, but all seedlings that are growing need more food than is in the cotyledons. The amt of sun and heat also affect the rate of growth, and maybe because mine are in a grhouse with full sun and heat at night, they are growing more, thus are able to utilize more fert.
I know annual plug growers start their seedlings on a fert regime from a very early stage, as do I- usually from the time that they are starting to put out their first true leaves. I use a weak formula for the first wk or so and then increase the strength until I transplant (usually after the 2nd pair of true leaves start to show) and then they get stronger fert every wk. When the roots start to hit the sides of the pot (3.5" 18/flat size) then I start with full strength.
I use a foliar liquid fert., and I get better control of the amt of fert that I need, its easier to increase/decrease if needed.

It may be that for the most part, I do vegetables, (tomatoes, peppers, eggplants) and direct sow everything else. I just don't care for the excessive top growth that fertilizer usually gives. I tend to want a bigger root ball than leaf area. I also only keep seedlings under lights for a maximum of 6 to 8 weeks. No more. When taken outside, they get fed, and my veggie garden gets fed 2 times a season. Once in Spring during planting, and the other when most everything has just set fruit. I've found that more than that gives lush top growth with very little extra production.

Every experienced seed starter has a system that works best for them, and by all means if it works, you got to go with it. It sounds like you have an excellent system that is quite successful. I've just found that over the years, the amount of fertilizer recommended by the fertilizer companies is more for their benefit, than for the plant's health.

Generally speaking, most seedlings get killed by kindness rather than by neglect. "Less is more" ... *most* of the time is the best. (especially, if you are unsure about what you are doing)

The only thing that I would add to that is that the more foliage you have, the better able the plant is to photosynthesize and grow more roots and vice versa. I also cut back most of the annuals that I grow several times before they go out, as I am looking for a bushier plant. So, you are right, what works best etc :) I would also add that the best way to get a good root system is to keep the soil on the dry side-letting the plant dry out before watering. Also, never fert a bone dry plant. Water first and then come back and fert a few hours later. The reason being that soluble salts tend to accumulate at the surface when the soil is dry, and that in addition to the fert you are adding, could burn the plant.

I don't mean to butt in here but have you ever tried liquid seaweed on your seedlings? I bounce between the liquid seaweed & the fish emulsion. That's all I use & it works wonders. It's also all I use outside too with the addition of alfalfa pellets.

Broots,

Isn't kelp liquid seaweed?

pennefeather, yes I think you are right. Great stuff.

Has anyone seen these squeeze-bulb sprayer anywhere? They are great for what is being discussed here. They are vastly superior to misting bottles, because you can get so much more water, gently, onto the seedling before the true leaves appear. Any tips would be greatly appreciated.
Thanks,
Dave

I'm more a fan of bottom watering, but for directing a gentle stream of water around seedlings without knocking them over, I like plastic condiment bottles. The squeeze bottles sold at beauty supply places would work fine, too.

I'm not a fan of top watering either, and try to limit the amount of moisture on any leaves, period. I simply do not mist seedlings at all. They are not like houseplants that benefit from having their leaves sprayed. The only moisture that mine get is from below.

After many failed attempts at seed starting years ago, I learned to avoid peat containers, and any moisture above the soil line. My success rate increased dramatically when I learned this.

Actually, I use the condiment bottle mentioned above mostly for watering in seedlings when I first transplant them (to settle the soil around the roots)... after that, it's back to bottom watering!

I'm with you on avoiding peat containers, too, Melody, although I do have a few plants in "cow pots" this year because I got curious about them!

I don't have too many probs with peat pellets, except that there always seems to be one pellet that just refuses to stay wet. But, as soon as I use up pellets, I think I'm changing to jello cups. One on the bottom, and one as the dome : ) Saw that somewhere on here......

Peat pellets and peat pots are different critters, and each has its own set of advantages and limitations... people tend to either love 'em or hate 'em!

With peat pellets, it often seems necessary to tear away some or all of the netting around the pellet when you transplant... roots don't always make it through the netting easily (despite the advertising claims).