Jesus christ... has anyone reliably solved the issues of weak growth in early veg under LED? What's the answer????

DukeFluke said:

Thanks for all the replies, I appreciate it.

From what age are you feeding at that strength? And, how different is that from when you were under HID?

Did you have issues trying to feed at the same strength you did using the old halides?

This might be where I'm going wrong.

Slow growth, lack of vigour, spindly stems, some interveinal chlorosis, and the leaves curling down away from the light rather than praying up for it. Generally slow shitty plants.

Nice. So what's your environment setup, ie temps/Rh/light distance etc

Thanks man

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A picture is worth a thousand words. Until then . . . we're all still guessing.

Maybe you're frying the seedlings with light – who knows? How are you measuring your PPFD? How many watts of light are you using over what area and at what hang height? If you're using strips I'm guessing you built the light yourself?

A picture is worth a thousand words. Ah, but I just said that.

Tip #1 If your tap water is hard, then it is usually a good source of calcium-carbonate and magnesium-carbonate (from limestone water sources). It can also be a good source of zinc, iron and copper due to leaching from the pipes. An exception is if you live near a desalination plant, in which case most of the hardness will likely be sodium.

If you use RO or demineralised water, then you will nearly always need an additional source of Ca and Mg, especially in coco (more of which later).

If you use tap water, your base EC must be added to the recomended EC. For example, with a base EC of 0.3 (my tap water), I can add 2.0 EC worth of nutrient for a total of 2.3.

But generally speaking, you also need to increase your EC under LED to compensate for lower transpiration. Just as you need to increase EC slightly in cooler weather and decrease it slilghtly in warmer weather. You need to adapt to the conditions.

In the mean time, a short story . . .

I have always used flowering nutrients full run, even in veg. With run-to-waste coco, the plant takes what it needs and the rest gets flushed. Flowering nutrients are always lower in N and generally lower in Ca and Mg. However, I never had an issue with them under HIDs because I had good transpiration and medium-hardness tap water (as mentiuoned).

Under LEDs it was a different story. Slow seedling growth, lime green leaves and pink stems. Always seemed to happen a few days to a week after they popped the surface. I did three things to fix this:

1. Reduced the amount of light I thought I needed. Call it denial, but I refused to believe I needed much less wattage over my seedlings under LED than I used to give them under HID. LEDs are very powerful. And I learned the hard way (initially).
2. Raised EC by about 50%. This was needed to compensate for lower transpiration.
3. Added Cal-Mag. Again, this was needed in coco under LED because I was using (and still do) flowering nutrients all the way through. I use a 3.3.1 Cal-Mag (3 parts N, 3 parts Ca, 1 part Mg).

Red-pink stems (as opposed to red-blue, which is genetic) are a dead giveaway to photo-oxidative stress. In other words, too much light. The plant produces a red stress pigment called anthocyanin designed to reflect red and blue light to reduce temperature build-up, especially in the stems and petioles. You see it a lot in plants that have been heavily defoliated because the fan leave are no longer there to absorb light and shade the stems.

The lime green leaves and slow growth (outside root stress inhibiting uptake) are due to low EC, but mainly nitrogen and magnesium, which are required for chlorophyll production.

If you are using cheap coco that has not been flushed and prebuffered, then it will be high in sodium and initial cation exchange will bind any calcium and magnesium and release sodiuim and potassium in its place. Ca and Mg are +2 ions. Na and K are +1 ions. Coco is negatively charged and will attract positive ions. Ca and Mg are more attractive than Na and K due to their increased ionic charge.

So it is important that your coco has sufficient Ca and Mg to begin with. Even prewashed and pre-charged coco can use a little extra Cal-Mag. It is hard to overdo calcium initially, because it is not really until you hit the flowering stage that it starts to compete with potassium and lock it out. Cannabis still needs a lot of calcium during the initial stages of flowering.

Overwatering is very rare in coco. If you have good drainage, it is almost impossible to overwater. I use straight coco – always have - and have never had issues with overwatering. And my plants get auto-watered 5-6 timres a day. The pots are always moist, but with good drainage coco will always have enough oxygen around the root zone.

With one exception: repotting. You need to be a little more careful going from a small to large pot that you only water around the base of the plant to begin with to encourage the roots to grow into the new coco. If you saturate the large pot, the new coco will take longer to dry, as there are no roots in it. The repotted plant will still grow, but not as fast until its root system starts to fill out the larger pot.

I need to stress that contintual auto-watering is a GOOD thing for coco, as each watering draws oxygen down with it and flushes out unused nutrient. This is different to hand-watering and leaving a plant to dry out by itself, because once the initial oxygen in the root zone is depleted there are no subsequent waterings to replenish it, and the coco needs to rely on evaporation to draw fresh air into the root zone. Coco will not suffocate roots like over-watered soil, as it does not hold as much water, but reduced oxygen at the root zone will slow growth.

Sorry, my "short story" is turning into a bit of an epic . . .

Back to the OP's problems.

DukeFluke said:

From what age are you feeding at that strength? And, how different is that from when you were under HID?

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I start at about 2/3 strength, or around 1.8-2.0 EC (1.5-1.8 EC plus 0.3-0.4 EC tap water, on average), and go to full strength by about week 2. Every time I water, I have a small amount of runoff – except right at the start when I saturate the pot and let it dry out a little as the seedling developes its root system. After no more than a week, I am watering to runoff.

As mentioned, I need more alround nutrient, but also a little more Cal-Mag. Canna Coco A&B already has more Ca/Mg than other base nutrient, but 0.5-1ml per litre of Cal-Mag will not hurt.

It is strain dependent, as indicas tend to be magnesium hogs compared to sativas.

Foliar feeding is the fastest way to correct a calcium or magnesium deficiency/lockout.

DukeFluke said:

Did you have issues trying to feed at the same strength you did using the old halides?

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Yes, as explained above.

DukeFluke said:

Slow growth, lack of vigour, spindly stems, some interveinal chlorosis, and the leaves curling down away from the light rather than praying up for it. Generally slow shitty plants.

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Sounds like a bit of light stress to me, but you'll need to give us more info.

DukeFluke said:

Nice. So what's your environment setup, ie temps/Rh/light distance etc

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No real idea what my Temps and RH are to be honest. I don't pay attention to the environment as much as I pay attention to the plants. They will tell me what they need.

What I can say is those seedlings were grown in the middle of winter when temps were anywhere from 5-10C overnight and 15-20C during the day. I compensate in winter with a higher EC.

Lights are my own and I will give them around 500 PPFD during veg, up to 600 PPFD later in veg, and that is measured with an expensive PAR meter (so my numbers are accurate).

Remember: if you reduce the amount of light, you can reduce the amount of nutrient – and vice versa. However, if you have too much light to begin with, increacing nutrient will not fix it. If your problem is too much light, and you reduce it and your plants start to thrive, then that is your problem. If you reduce the amount of light and the plants bounce back but are still a bit slow, then your problem is two-fold: light and nutrient.

The way to tell the difference is, reducing the amount of light should aleviate pink stems and bleaching (yellowing/bronzing) of the upper leaves but if you have a nutrient deficiency at the same time, you will still have yellowing of the lower leaves (N) with possible interveinal chlorosis (Mg) and random rust spots (Ca), usually in the lower to middle part of the plant.

Did I mention a picture is worth a thousand words?

DukeFluke said:

It's staying wet a lot longer tbh, but this doesn't seem to be an issue once they get fully going. It's this initial struggle that really frustrates me.

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It sounds like your environment is within a safe range, but possibly too much light too soon/potentially overwatered.

If your plants are not drinking like they should, they may possibly have gotten stressed from too much light too early, or getting overwatered, or a combination of the two. This will effect the plants transpiration/how much they drink. If they can’t transpire/uptake water easily, you will notice your media staying moist longer, which can lead to low oxygen levels in the media which can cause all sorts of other issues (nutrient uptake and lockout/pathogen infection/root illness).

Coco Media that stays wet too long (plants not drinking/overwatering), in my experience, will often have a very high EC and will drop your media PH like a rock in a pond making for very acidic conditions, which also affects passive water/mineral uptake. This makes your plants even less likely to drink, even if your environment is in check. If this happens early on, it will set you up for snails pace growth and unhealthy plants as root growth/nutrient uptake is inhibited.

My next diagnostic step would be checking your coco EC/PH. I would do this by measuring your feed solution, checking your runoff solution and comparing the results like @Rocket Soul already mentioned. One thing I would like to add is (if you have the ability) checking the PH/EC of the coco in your pots. Checking runoff is a helpful guide, but still won’t tell you exactly what the conditions of your coco media are.

When I ran coco/Jack’s, I was using a Soil PH meter & Soil EC/Moisture meter so I could gauge how much feed solution was needed to “flush” the coco. Just because your runoff results look in range, doesn’t always mean your media conditions are as good. Like I mentioned, checking runoff is a decent guide, but not the only thing to consider.

You could also lower the light intensity/raise the lights a bit to see if you observe a positive response like @Prawn Connery mentioned as well. This would be advised if your plants look stressed in general, until you can pin-point the true cause of the issue.

Because we don’t know what your plants look like, I’m linking some posts from the “Led Lights = More Mg?” Thread as someone posted some decent photos of light stressed plants. There’s also a YouTube video showing some examples of light stressed plants in the same thread.

If your plants look similar, which it sounds like it based on your description, I would back the light intensity off a bit and check your media as mentioned above. Once your plants start drinking more and improving their appearance, you can slowly begin to increase your light intensity. You’ll just want to read the plants. This is much easier to do when you know that the other variables (environment/media EC & PH) are within a safe range.



Good Luck Grower

It's sorta hard to read between the lines....... lol


Here's the skinny on temps etc


Everything sounds ok to me in that department
I'll hand it over to the coco guys now

was mentioned several times allready, intensity is the main problem.
i do still use also 3000k blux, same as you.
it pretty much never works out blasting them with light in veg.

repotted, put in the tent on 22th oct., slightly stressed allready, had been for too long in the vegbox and got too close to the cxb cobs, been in tiny starter pots also.

they basically couldnt stand much more then this.

this is from 19th nov., 29 days later.


quite some nice green and i couldnt complain about slow growth, they where 13 days in flower at this point above.
i noted down that i went to 700ppfd on this day.

in short, dial down to 20% and watch your plants recover, when they have developed more leaf mass (able to collect more photons), dial up.
its the hardest part of the led learning curve to only give them what they can take.

Thanks @Moflow

This is exactly what I'm talking about. And I notice the same thing when I pot up into final pots, around 20-30L or so...

There's got to be something to this. Maybe the plant needs more root mass to effectively process the light, I don't know.

Anyway, I've watered them with 2.2 ec canna base, as suggested, so let's see how they go. I'll get some pictures up to show them

Clones need to harden off mate. You can't just take them from a few watts (or whatever) of cloning lights and put them straight under 500-600PPFD of LED. They need to accumulate chlorophyll first before they can absorb all that light and use it for photosynthesis. If the plant can't photosynthesis the light, then it just builds up as heat, which creates photo-oxidative stress.

In the old days, if you had a sick plant outside the first advice you were given was to put the plant in a shady place to help it recover. You also learned not to sprout seedlings or put clones out in full sun. Same principle applies indoors.

DukeFluke said:

Honestly I'm thinking at this point to just get myself a t5 fluoro and go back to doing it old school.
In all my years growing, I just put plants into coir, fed them 1.0ec of a base feed, and stuck the fluorescent light on them and watched them boom. two weeks and a pot up later and I'm almost ready to flip...

But under LED there seem to be so many fuckin variables that I'm really feeling quite demoralised by it. I feel like a new grower again trying to figure it out, and I'm far from it. Brought the temps and humidity up, all the usual fixes which have sometimes worked in the past

Is it possible that the spectrum of the Bridgelux gen 3, 3000k whites is causing the issues in the first place? Or is the high ppfd demanding a higher strength feed or some co2?

Is anyone finding problems using similar lights?

Thanks ahead of time people

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don't you think that depends om the strain? I'm growing some grandmommy purples with leds and she isn't take this long

Prawn Connery said:

Clones need to harden off mate. You can't just take them from a few watts (or whatever) of cloning lights and put them straight under 500-600PPFD of LED. They need to accumulate chlorophyll first before they can absorb all that light and use it for photosynthesis. If the plant can't photosynthesis the light, then it just builds up as heat, which creates photo-oxidative stress.

In the old days, if you had a sick plant outside the first advice you were given was to put the plant in a shady place to help it recover. You also learned not to sprout seedlings or put clones out in full sun. Same principle applies indoors.

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I understand this mate, but there's more going on than hardening off.

I used to take clones and put them straight under high intensity lights and watch them explode. There's clearly a difference using LED lights that is specific to LED. There's no doubt about it.

The higher strength feeding is definitely paying off though. I've been giving them 2.0ec and it's made a huge difference, especially to the young clones that I just started off on this feed. I'll get some pics up soon

I can't remember the figures but 4x t5s isn't a huge amount of light.

Moving from t5s to led I used the same light intensity with the led I used with t5s.
On paper that might work out in practice it didn't, that could be for reasons I'm overlooking idk.

I've questioned the intensity versus the quality but you know what it's like, nobody wants to hear it.
I use led but I'm not convinced it's a all out better spectrum for growing I actually think hps is the best all round for growth rates,
I still use led for the other obvious reasons.

Star Dog said:

Moving from t5s to led I used the same light intensity with the led I used with t5s.
On paper that might work out in practice it didn't, that could be for reasons I'm overlooking idk.

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T5s are inefficient, so act as a heater. If you replacd the light intensity but don't adjust for the lower temps you're not comparing apples to apples. It is just more complex than replacing one light with the next and then blame the changed (worsened) environment on the lighting technology.

Star Dog said:

I can't remember the figures but 4x t5s isn't a huge amount of light.

Moving from t5s to led I used the same light intensity with the led I used with t5s.
On paper that might work out in practice it didn't, that could be for reasons I'm overlooking idk.

I've questioned the intensity versus the quality but you know what it's like, nobody wants to hear it.
I use led but I'm not convinced it's a all out better spectrum for growing I actually think hps is the best all round for growth rates,
I still use led for the other obvious reasons.

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Some of you might be aware I only change to led in the height of summer.

DukeFluke said:

I understand this mate, but there's more going on than hardening off.

I used to take clones and put them straight under high intensity lights and watch them explode. There's clearly a difference using LED lights that is specific to LED. There's no doubt about it.

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As I said, we're guessing what your plants look like so it's hard to know 100% what the problem is. I'm glad the higher EC is paying off for you. Cal-Mag might be your friend – as much for the nitrogen as the Ca and Mg. It will raise your EC a bit, too.

The contribution of CalMg to Nitrogen levels is minimal.

For example, GH CalMagic has 1% Nitrogen, or 3 ppm N per ml/G.

Lou66 said:

T5s are inefficient, so act as a heater. If you replacd the light intensity but don't adjust for the lower temps you're not comparing apples to apples. It is just more complex than replacing one light with the next and then blame the changed (worsened) environment on the lighting technology.

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I'm not 100% buying this theory tbh. When I used T5s I used to have a fan blowing through the vents and could touch the bulb with the back of my fingers. They were at least as cool as my leds, if not a bit cooler.

It's possible it has something to do with the diffuse light shining through the glass tube rather than the point focus of the individual diodes, because in terms of the most significant difference between them, that's it.

cobshopgrow said:

was mentioned several times allready, intensity is the main problem.
i do still use also 3000k blux, same as you.
it pretty much never works out blasting them with light in veg.

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Hey Cobs, what's your feed strength during this period?
Thanks

for the ones above, hard to say this time as i tried a few rounds half assed organic growing.
had been recylced and recharged soil, was/is a lot EWC in it and other stuff.
well, they had been well feed at that point for sure seeing their green.
will do more with salt soon again, but as i grew so much in soil with EWC and organic fert pellets recently i hesitate to throw out a number... but may would give them 1.5 (IF it was a salt grow).

DukeFluke said:

I'm not 100% buying this theory tbh. When I used T5s I used to have a fan blowing through the vents and could touch the bulb with the back of my fingers. They were at least as cool as my leds, if not a bit cooler.

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T5s have an efficiency around 0,7 µmol/J, LEDs have 2-2,8 µmol/J. So for a given amount of light T5s produce 3 times the heat that an LED does.

The quantum board style LEDs are quite diffuse. They don't lose much to T5s in a real world scenario. COBs are worse of course.