Can too much light hurt seedlings?

I started seeds 3 weeks ago in rockwool cubes. After sprouting, I used a weak nutes solution for the seedlings as recommended by the manufacturer (4-6-7 @ 1 tsp./gal. of water), kept seedlings at around 1- 2 inches from floros lamps, 24 hours /day except on sunny days when they were moved to the window sill. I fed and watered the plants by hand, flushing the rockwool with nutes solution at least once per week and watering as needed with just plain water between feedings. At two weeks old and two inches tall, growth began to slow, and the new leaves began to curl downward, although no yellowing occurred. I moved the seedling to four inch rock wool blocks, kept up the same nutes / watering regiment, and moved the seedlings under a 400 watt sodium lamp at a distance of about one and a half feet, 24 hours / day. The problem only worsened. The seedlings, now at three weeks and only 3 inches tall, stopped growing all together, and the new leaves are tiny and curling downwards, but still no yellowing. People have told me the problem must be high nute concentrations, but I disagree for several reasons and have not deviated from the manufacturerâ??s recommendation. First, the solution I am using is weak, and I only use the nute solution when I noticed the leaf color just start to turn a slightly lime green color signaling the need to replenish the nutes. That happens about once a week. The rich green color quickly returns within the a day or two. Second, nute buildup, is unlikely to occur in just 2 - 3 weeks. When I moved the cubes to 4 inch blocks with no improvement, that pretty much proved conclusively that nute buildup was not the problem. Third, this is my fourth attempt and had the same dismal results.With each attempt, I cut back on the nutes from the manufacturesâ?? recommended dose, as everybody recommended, until I got to their minimum level, the â??lime green color.â?� And finally, I never saw the usual early warning sign of over fertilizing: the dark forest greening of the leaves which eventually turn almost blueish. Instead, I suspect the problem is too much lighting, since it is the only variable I have not change. I think by keeping the seedlings rather close to the lamps (1" - 2" under floros, 24 hours/day, and full sun when available, or 1- 2 feet under a 400 watt sodium, 24 hours/day is not quite enough to burn them outright, but intense enough to wither them slowly, like what happens with over fertilizing. What do you think?

did you prepare the rockwool first?you must stabilize the cube's and block's ph before their used,by soaking them in a ph solution of water adjusted to 5.0 for 24HR's before you use them,or else they will be too alkaline for the plant's....bonbon

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Originally Posted by bonbon

did you prepare the rockwool first?you must stabilize the cube's and block's ph before their used,by soaking them in a ph solution of water adjusted to 5.0 for 24HR's before you use them,or else they will be too alkaline for the plant's....bonbon

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No, I did not. I heard of the alkalinity problem with rockwool. I also know and witnessed some who never stabilze their rockwool and do not have a ph problem. However, for them, like me, they do not use an active hdro sytem, rather we hand water. One inherent problem with hand watering is the tendency for the raockwoll to build up nutes, salts, and become acidic. Whereas the acidic problem may be appearent in a more netrual medium, in alkaline rockwool the " acid problem" associate with hand watering serves to neutralize the rockwool "alkaline problem". However, the rockwool alkalinity problem may still be prevelent at least initially until multiply nute feedings have brought down the ph. Since I handwater, rockwool alkalinity has not been a problem except when sprouting seeds od I would assume cloning. The reason being that during these earlystages very little nuts solution is used to counter the rockwool akalinity. This doesn't seemed to be a problem at later life cycles when using blocks and slabs because much more nutes are used to quickle nuetralize the rockwool. I recommend that when hand watering, one needs only to stabalize starter cubes for seedlings or clones, and not worry about the big blocks and slabs. A tell-tale sign that the rockwool is too alkaline will be a slimey, geasey feel in the water and rockwool. Thanks for the tip. Now some good news. My plants are recovering. The problem seems to indeed been the keep the plant either too close to the lamps of for too long. I moved the plants to the widow sills for a full day sun, and no more. They slept in the dark at night. I also gave them a does of nute because of the lime green color. No they a doing beautifully. Dark green color has returned and leaves have no more curl.

I'm glad to hear that the plant's are rebounding,but i'm going to have to disagree with you about the necessity of leaching the rockwool of the lime and calcium,after i stabilize and set the rockwool up i adjust the(reservoir) solution to 5.5,and recheck after the first flood cycle is complete,and there alway's is a slight rise of 0.3-0.7 at which time i re'adjust the "ph" lower to about 5.8 to where it usuaully stay's,then i check the block's with a soil "ph"tester at where their around 6.1-6.3 and there the reading's will be consistant throughout the rest of the grow,i flood my system at 8hr interval's.each cycle is a1/2hr.at the rate of hand watering you're using, it will be sometime before the medium is stable,in the meantime you are risking a secondary nute lockout,but if the method you use is working out for you by all mean's, then use it.as far as you're lighting goe's,I also use a 430WT hps that i keep at 12" above the canopy,with a overhead exhaust and a occilating fan between the plant's and lamp,sorry if i sounded critical,i did not mean to,just a simple disagreement,welcome to the forum and keep us posted on you're grow....good luck....bonbon :D

glad it looking better for you
i hate to think of dying plants
sad sad shit that is


i dont know nothing about hydroponics
i hope to learn a lil something here myself
so please anything of value to the mind you have learned
i will enjoy reading about

thanks for helping others

peace

Hey Bonbon, you were right about a secondary lockout. Alas, the symptoms started to occur again. Frustrated by a year of rockwool ph problems, not to mention problems with its disposability, nute and salt build-up, maintainace of handwatering, expense, and limited results even under ideal conditions, I decided to abandon to use of rockwool as a media altogether, and instead purchase a high quality manufactured system.

Looking at the current technology available, it appears that aeroponics is the way to go, if one wants to get the best. So my questions are for anyone familiar with aeroponics. For the first question, is aeroponic technology the best system money can buy? What are its pros and cons?

I've notice that all of the areo systems are designed for a two tiered operation, either cloning systems or growth systems. How does one coordinate the timing of a three phase operation that involves rooting, growing, and flowering, with only a two tier clone / growth system set up? I guess you can simply solve the problem by buying two full-blown growth systems, and use one for growth whlie the other for flowering provide you have two large room and separate rooms for each system. But in my case, and probably for most, I have niether the cash or space. I have a 5' X 6 ' room, big enough to accomodate a full-size growth system, and a 2' X 5' room big enough for cloning machines. To coordinate three growth phases with a two tier system, some overlapping purpose with either system is in order. For example, it seems that some of the early veg growth could be done in the cloning machines, because most cloning machines use two inch root baskets> This allows for substantial development of the plants before they begins to crowd. Once the plants have been allowed to reached their maximum limit in the cloning machines, they can then be move to the large growth system in the large room. Here is where the timing gets alittle tricky. Moving plants to the larger room has to be timed with the havesting of the flowering generation which previously occupied the large system / room. After the plants are harvested in the big room, the mature clones (which can be considered young plants atthis stage) are moved into the large grow system where they continue their veg growth until their desired size is reach for flowering. During this part of their veg growth phase, cuttings can be taken for the next generation of clones. After then cuttings are taken the plants can be left alone continuing their veg growth until they reach their desired size for flowering. Does this seem like a plusible operation or am I way-off base?

I also notice that all of the aeroponic systems are very compact and retailers claim the systems are not meant for really big plants over three feet like inteterminate tomatoes. They usually employ five inch root baskets spaced every eight inches on center. This seems to be the industry standard. The compactness of these figures indicates to me that the plants should be grown using the "Sea of Green" method. If this true, do the small tightly space plants need support other than the basket lids or clay pellets that come with these systems?

And one final and really dumb question: how do you germinate seeds with an aeroponic system?

The last straw that led me to give up on rockwool was when I took Bonbon's advice and soaked the rockwool starter cubes in a 5.0 pH solution for 24 hours. I also used and a mild "for cloning" dose of ferts too before using them. I planted tomatoes seeds in the cubes, and for a comparative experiement, I planted the same seeds in regular potting soil. The potting soil won hands-down. After almost two weeks the tomatoes in potting soil are 4" tall while the plants in the cubes were only an inch or two. And there was far better germination with the potting soil too. Admittedly, it is possible that something still isn't quite right with the rockwool starter cubes i.e. nute lockout or pH, but I doubt they can be that far off at this early stage, because there isn't much that can go wrong sprouting seeds. If there is indeed still something wrong with the rockwool preparation, then it has got to be the most finicky and unstable media known. I'd lke to know if any successful rockwool users ever made comparision with potting soil. I have heard an almost unanimous consensous that any hydroponic system is far faster than soil, but can you explain what just happened in my experiment? :rolleyes:

Some grower's do experience the problem's that you mention with rockwool because they use the wrong application's,they either tend to over saturate it or the ambient tempeture's are too low or unstable,unlike soil,rockwool hold's a lot more water and oxygen and it's very porous,which make's it more sensitive to atmospheric condition's,that could be why the outcome of you're experiment gave you those result's,i started in soil(like most grower's) and used it for a long time,the convenience and low maintinance,not to mention being lightweight and economical as well as the cleanliness,make's it the medium of my choice.i think if you do a little more research,you will benifit from the advantage's of using it. http://www.mellowgold.com/grow/rockwool ....bonbon

Thanks Bonbon for your advice. Nonetheless, I'm still determined to go aeroponics instead of rockwool. Now you must be thinking, "this guy cannot get it right with Rockwool, how can he expect to succed with areo?" The reason is not that I cannot suceed with rockwool, but that I cannot succeed with a handwatering system. I am certain rockwool would not be a problem if I used it properly in an flood or drip system. As you said, the instability cause by handwatering leaves too much to chance. Since I have to invest in a new system anyhow, I might as well go with the best that is out there. So I go aero. :p

All the responses you got were right on. I have a website at www.growweed.com and think you might benefit. There is an exerpt from my book on the Cannabis.com website under hydro. Check it out before you spend any more time and money. You already have all the right tools and are on the right path.....Coloradojane

I buy regular potting compost at my local garden center,I use tomato plant food in every fourth watering.I got some slow release nutrient tablets off the net and my plants are coming up like prize winners.
PH balance ? rockwool?? pissing about ????
Stick em in the pots,light em,feed em,water em,harvest em.Simple ??

Smoke em. LOL

when you just planted the seeds how much light should they get till they sprout

that may work fine for you psychoat, but do you think you are harvesting the same amount of grams per plant as say, colorado jane? Hmmm

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Originally Posted by DirtyLinus

that may work fine for you psychoat, but do you think you are harvesting the same amount of grams per plant as say, colorado jane? Hmmm

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Yes