I planted around 230 seedlings in rockwool.
They are not growing but the leaves are turning yellow and more and more of the seedlings are dying. I already lost more than 30 because of that.
I really don’t know what it is.
I have HID lightning 400W in 120cm distance. I have running a big dehumidifier set at 65 percent. Seedlings are in small rockwool cubes in a heated plastic basin set at 26 degree celcius. I started fertilizing after a week. I use tap water and regulate the ph to 5.5 before feeding.
Problems started before fertilizing. In beginning I had t5 lights, but all of the plants stretched, so I hanged the lights lower but then the leaves hang down and wilted. That is when the shit started. I put the lights higher and then plants in the periphery started stretching because the tubes were too short. So I had to put the plants under HID lightning. 400 W distance 120cm. Since then the plants don’t do anything anymore, the weaker plants slowly crumble… :-/
I am watering the plants once a day since the rockwool dries out really quick. I am not sure if I maybe overwater them. Because sometimes there still stands a bit water in the basin after I gave them water. The cubes soak themself full. If I dont do that they dry out too quickly. I don’t cover the rockwool cubes as it is too many of the cubes. I mean how wet is too wet? Will my small roots be able to drown in rockwool? I heard there is so much air in rockwool that the plants can’t drown. If there is residue water it is not so high.
It is a bit of a pity, as it is around 500 bucks worth of seeds. I am not sure what is the reason the plants are fucked up and if I need to start over. Maybe you can give me advice. Tomorrow I try to send pictures. I didn’t want to post pictures because of security reasons. But in that case I will do.
(I was not able yet to install the air exchange fan of the room. The room doesn’t get hot and is dehumidified. Also when I am working in there, the small plants should get enough CO2).
Are the plants maybe light burned and then overly sensitized to all other influences???
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Looks like a refresher course is in order.
There is a FAQ section that may have exactly what you are dealing with.
Light burn may have been the first assault, not sure.
Do you treat the rock wool blocks before you place the seeds in, or straight water (pH) ?
Are you feeding these things in the first week of life?
and on and on the questions go.
Pictures are worth a thousand words.
Are you planning on going hydro?
Soil is an easy place to start!
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I’ve just answered your thread on RIU. Soak the cubes in PhD water several times. Lightly squeeze the cubes and check the water ph that comes out. Rock wool cubes are a nightmare for ph stability. Even the ones advertised as ph stable I’d soak several times.
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How about some pictures so everyone can see what the problem is… Would go a long way!
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I squeezed a cube where a dead plant has been inside. Over 7.5 ph!!! Only in the very beginning I didn’t ph adjusted the water. Since then I always feed 5.5. So the watering in the beginning messed the cubes ph for longterm? How do I get that shit out of the cubes?
I will do now a solution of 5.5 (maybe better 5.0?) and soak the cubes and squeeze them out carefully. Hope that will do the trick. Hope the plants are not too much strained already…
I got a hid at 120cm at 400W. Should I reduce to 250W at that distance?
Here are some photos of the nightmare.
Light burned, over watered, under read. 230?! Plant as many seeds as pages you’ve read on the subject is my best advice.
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Grodan comes with instructions on soaking right on the package.
I read a book from spear. He said he bought cultilene because there is no need to presoak. Also you can contact grodan. They recently changed their product also so that you dont need to presoak them anymore but still they ship the product out with that instruction. So it seems that I did read more than you about that.
I had several grows with soil indoor and outdoor and it was pretty easy and there were never problems.
Let the cubes sit in PhD water for a few days before putting seed in to allow it to stabilise. I absolutely hate rock wool for this exact reason.
Even if they say pre soaking not required I’d still do it anyway. Rock wool is a nightmare for ph drift. Give jiffy pellets a try next time.
@SamandMax I literally sent you the info from grodan directly. They’re pH balanced, but have residual dolomite lime. A soak is still needed.
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I would lower your heat down to 20-22 , I think you have too much heat on the roots !
Edit : in addtion to the ph issue others are stating * combination
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I flushed each single cube with ph adjusted water several times and squeezed them a bit.
I lowered the HID light a little bit but reduced the wattage to 250W.
Also I lowered the temperature to 21 degrees.
I disinfected the basin and made sure that there is no residual water after flushing.
Also I added 1ml of H2O2 12% per Liter of Water for the flushing.
Tomorrow I will give fertilizer.
But I guess I need to buy some new seeds too.
Question: If I can rescue and stabilize the plants, will they show deficient qualities the rest of their lives, e.g. reduced yield, or will they behave normal? My plan was to select mother plants. If the plants show unusual traits because of the severe stress as seedlings, the choice might be flawed?
Oh and I contacted Cultilene and Grodan about the necessary pretreatment.
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Generally speaking regardless of brand, soak for 24 hours with the ph adjusted to 5.5 if there a lot of cubes or 5.8 if only a few cubes. EG 10 cubes in 10 litres 5.8ph, and 50 cubes in 10 litres 5.5ph. This is after adding what evr nutrient solution your pre mixing with. A very low EC/TDS advised.
If given 24 hours they should be reading around 6.0-6.2ph I have always found.
If your tap water is higher than 7.0ph to start may be go as low as 5.0ph to soak
Going yellow and wilting may be they starved to death…no food 
If you want to soak a thousand cubes just use the math / ratio above, depends on the size of your reservoir for soaking
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Not that hid light is bad, but flouro would be less heat and can be placed closer. I use cfls to veg under personally. I don’t know what’s causing your stretching issue there, but it does seem they’re stretching out.
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Use jiffy pellets. I’d not use any kind of rock wool at all. With it being your 1st grow I suggest you should have grown in soil 1st and got a growing or two under your belt. Soil does not need your water PhD.
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I had to put the seedlings under hid lightning because the t5 which were delivered with the greenhouse were too short and too high (some crappy plastic holder to put on the greenhouse). In my opinion a misconstruction. I did another construction with these tubes but they were too short. I would have needed 120cm. The plants in the periphery were just stretching. I am getting now a 120cm 8 bulb reflector with adjustable amount of bulbs.
Unfortunately it seems that the flushing had not a good effect. The plants are still dying, now it seems even a bit faster. Maybe I handled the small cubes to rough while flushing. Or they were too stressed and almost dead anyways
When I squeezed a cube with a dead plant inside I still got a ph of 7.8. Even when I flushed the cube several times.
Maybe it is normal that the plant increases the ph of the cube? So far it seems the ph in the cubes never changed. Even with flushing.
I guess this experiment is now finished. Have to start over. Didn’t expect that hydroponics in the seedling stage is that unforgivable. Also I didn’t expect that if I buy a product about which it is said in a book by a renowned grower that you dont need to presoak it, you will have wished to do otherwise. But who knows, maybe that wasn’t the problem even…
I got some questions. I got now calcinit and epsom salts to do my calmag stuff. I still have some hundred liters of osmotic water around. The water is from last winter. Can I still use this water or is there some chance that the water is contaminated now in a way which will fuck up my seedlings again? Maybe I could add H2O2?
Also I am not sure if I still want to do rockwool if I need to presoak it. I got five ebb and flow tables. I wanted to do a perpetual SOG. What could I use instead, which doesn’t create too much hassle with lot of plants?
Because I got a lot of rockwool around now, I am also thinking about just doing the seedling stage with something different than rockwool starter plugs and then transfer it 10cm x 10cm rockwool cubes and slabs that I got. Could that work? Can you recommend anything for the seedling stage? Maybe these coco tablets are good?
Jiffy pellets. Bin the rock wool altogether. You maybe just had a bad batch sold to you.
For shits and giggles I cracked this seed on friday. I put it into soil on Sunday into a biodegradable pot. I plan on sticking it into the ground outdoors hopefully this weekend. I have not touched a ph meter once or adjusted the ph levels and my tap water sits at 7.5.
Soil maybe the best option for you.
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I think the flushing may have been too little too late, the damage had already been done.
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I can’t work with soil in that size. How could I do a SOG with four 1.2mx1.2m tables with soil?
Actually it is not my first grow. And I never ran into any big problems. Also before I did a SOG with 50 plants from seeds in soil and it worked perfectly.
I never expected that all my seedlings would just die in the beginning. And I am still not sure about the reason.
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