Noobie Lettuce Raft Problems

efm7November 6, 2010

Hi there, I am currently attempting to grow "Green Deer Tongue" lettuce in a raft under a couple of high output T5's growing using Pure Blend Vegetative nutrient solution.

My lettuce is looking very thin and tender...

This is my first attempt at growing anything since i grew beans in wet napkins in kindergarten. LOL

this is my guesses as to what the problem could be:

- wrong variety of lettuce to grow hydroponically

- lights were initially too little and too far away (corrected this recently by adding a second T5 and placing them closer to the plans)

- bubbles from air stone not getting consistent coverage

- plants grown in jiffies were put into the system too soon (no roots were sticking out)

any advice is appreciated.

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If it helps any, there's a step-by-step guide at this site with weekly pictures:

From my perspective I'd say your light may have been too far away, it would also be worthwhile checking your EC to make sure they are getting the required amount of feed.


    Bookmark   November 7, 2010 at 5:36AM
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I don't' use artificial lighting so I don't have any first hand experience with it. But I to would be wondering about there being enough light intensity. But taking a closer look at the pictures, I think the roots are suffocating. The water level looks like it goes all the way up to the top of the growing medium. I set the water level so that only a small amount of the baskets are submerged. That is enough to wick up moisture but not suffocate the roots in it.

Also I have no idea how much air bubbles you have going in the reservoir but the more the better. That said, my lettuce plants did surprising well with half of the air bubbles the air-pump was superposed to put out. I just had the dual output air-pump from Walmart that's supposed to work for aquariums 30-60 gallons. One of the dual pumps went out before I ever started the lettuce plants, so only one side was working. I had 8 lettuce plants growing in a about 6-8 gallons of nutrient solution with only half of a air-pump working.

I don't' know if you have sufficient lighting (that may be a factor as well), but I think the roots are suffocating with the water level so high.

    Bookmark   November 7, 2010 at 5:53PM
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Thanks for the ideas,
the lights put out a total of 4400 lumens, im always hearing mixed numbers.. i've heard between 1500 and 6200.... so much different information i have no idea what to believe :(. I am in Canada so natural light is not an option.

I'll raise some of the plants a bit higher to see if it helps, but they used to be high to begin with and I had recently lowered them.

EC meters, I don't have one, how much should i spend on one?

I have the Elite 801 air pump for this lettuce raft. Im not convinced im getting enough coverage. the air stone is loose at the bottom and moves around throughout the day, and the plants that receive less bubbles only get a few bubbles a second.

I also notice that the plants receiving less bubbles are yellowing a little.

good news is that the leaves have gotten much wider since first post.

    Bookmark   November 7, 2010 at 11:02PM
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The bubbles don't directly affect the plants. they add air to the nutrient solution which the plants then consume. So whether or not they're directly hitting the plants should not matter.
They look too wet to me. you can see standing water at the top of the hydroton. your plants should be set so that bottom of the medium just touchs the nutrient solution. The medium will wick up what it needs from there.
The lights may be a problem, but they don't appear to be excessively high right now. Remember its not the lumens put out by the bulb you're concerned with, it's the amount striking the plants. light diffuses very quickly, especially with flourescents. That's why you keep them so close.
I wouldn't worry to much with EC just yet. pH is much more likely to cause problems than EC (assuming you're mixing according to the manufacturers directions) and even that isn't likely to be locking out the primary nutrients to show the problems here. I'm not saying it's not important, just not yet.
I say start with the water level. Those plants are swimming.

    Bookmark   November 8, 2010 at 8:54AM
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yeah waterlogged, even just below the bottom of the net pots if you have enough air stones, the air bubbles breaking on the surface splash water up into the netpots/medium.

    Bookmark   November 8, 2010 at 11:40AM
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splitsec002(z9 CA)

Your plants actually look fine to me. They might be a tiny bit water logged like grizz says but I've grown raft lettuce like that and the plants always look weak in the beginning. After some time they will take off. If anything I would increase the light. Just give it some time. They look ok for that stage of growth.

    Bookmark   November 8, 2010 at 9:06PM
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Karen Pease

General lighting rule of thumb for fluorescents, HPS, and MH: if you place your hand where the plants are, the lights should feel comfortably warm. If you're not feeling the warmth of the light, they're too far; if your hand feels uncomfortably hot, they're too close.

    Bookmark   November 10, 2010 at 1:56PM
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I've got to agree with the grizzly guy. I've started a slew of plants in hydro and plant after plant (tomatoes, lettuce, basil, peppers, citrus trees: tangerine, lemon and orange, plus others). The roots need oxygen, the kind found above the water line! Every hydro method I know of makes use of at least some of the roots getting oxygen without being submerged in water constantly.

To wit: I just got into trying to grow dwarf citrus trees. The first plant I moved from their potting mix to hydro was a lemon tree. I put it in a net pot after washing all the potting mix off and submerged all the roots in the DWC system. It was doing poorly. So I removed some water so only about half the roots were submerged. It's starting to grow new roots.

A few days ago I added an orange tree, but this time left the potting mix on, Stuck it in another DWC bucket so just the bottom 1/2" of the roots are in water. So far (knock on wood) it isn't showing any signs of stress.


    Bookmark   November 10, 2010 at 9:33PM
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The lettuce is doing much better now that i raised the net pots about an inch higher, pictures to follow soon!

    Bookmark   November 13, 2010 at 1:29PM
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I've been growing 4 varieties of leaf lettuce (39 plants) in 3, 9 gallon flat plastic containers and have had generally good results for 9 months now. In one, I have 2 stones. In the others I have 2 open air hoses each. I cannot discern any difference.

My biggest problem has been ph control. The ph will drop to a 5 or less within 1 week of changing to new solution. That seems to have a significant effect on plant growth. I start with neutral (7) water so I'm not sure why this happens.

I've also noticed that if my solution level is too high the stem bottom rots.

I grew lettuce in my GH (in hydroponics) through the hottest part of summer, although they bolted sooner. I've never been able to achieve that before in spite of the fact that I live at 7400' in SW Colorado.


    Bookmark   November 14, 2010 at 9:24AM
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Do you measure the pH right after you mix the new solution, or just measure the water before you mix it?

P.S. What city in CO? I'm familiar with most city's on I25 and I70.

    Bookmark   November 15, 2010 at 3:14AM
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okay so here's what the lettuce looks like now

    Bookmark   November 15, 2010 at 7:08PM
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I am a newbie at this hydroponics things, less than a year. I am quite excited by the results so far, though. I check my ph a week or so after changing the solution.

I live near the Pine River between Bayfield and Vallecito, about 20 miles east of Durango. Very beautiful, but quite snowy and an extremely challenging area for gardeners.



    Bookmark   November 15, 2010 at 9:18PM
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The nutrients themselves will changing the pH of the nutrient solution. If your not checking/adjusting it right after you add the nutrients to the water, the pH will be different than it was when you checked the pH of just the straight water. The elements in the nutrients affect the pH as well as any buffers that are in them. It doesn't sound like anything is wrong, just test and adjust the pH level right after you mix the solution. I personally never bother to check the pH of the water anymore before I mix the solution, I just don't see a need to test it twice when the only one that really counts is the one after the solution is mixed.

Ya that's a extremely beautiful part of the country. Most of my runs to Denver took me over the 70 and up the 25 (depending on time of year and/or weather), but I have gone through Durango a few times. Once when the sent me from Denver to Farmington NM to pick up a load, and the other time I had some Volvo's to deliver to the dealer in Durango. It was winter that time. I also remember a time going that way when I stoped at a Indian consino at four corners. They had some "fall off the bone baby back ribs," on the menu, and they weren't kidding. Those ribs were so tender you could just pluck the bones out with your fingers, and eat the meat with a fork. My favorite times travailing were going through the Rockey Mountains as well as the Northwest.

    Bookmark   November 16, 2010 at 3:50AM
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I have tested my solution right after mixing and it's only slightly acidic. Within a week the ph drops significantly. A bit of a mystery.

The water I use is very pure, the Pine River is pristine and originates in the Weminuche Wilderness in pre-Cambrian formations. The town of Bayfield sent me an analysis of the water (I haul water 8 miles from town) and it's very clean. If anything, it should be slightly basic, since the last few miles of river are in Leadville limestone fm. The intense mineralization found at the head of the Animas River (next river to the east) and within the Silverton Caldera is absent on the Pine. ( A natural spring near my cabin at 10,700 feet elevation and above Silverton runs a ph of 4!)

I use Dyna-Grow, maybe that contributes, but I suspect the minerals in the water play an important role. Maybe some kind of reaction. But as I said, it isn't immediate.

If you drove a truck over Red Mountain Pass in winter, I'm sure you won't forget it. You might have come over Wolf Creek Pass though, quite easy by San Juan standards.

My daughter's father in law rode a semi loaded with farm implements off Red Mountain Pass in January of 2009 over a four hundred foot cliff. Backwards, which is what saved him. He ended up in the stream below and the trailer acted as a shock absorber. The next time you travel Red Mountain, look over the edge at mile marker 89. No one believes he lived through the fall.


    Bookmark   November 16, 2010 at 8:49AM
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FWIW, I mix my solution, let it set overnight while being aerated, then test it before adding it. I have found, repeatedly, it falls from a reading not long after mixed.


    Bookmark   November 16, 2010 at 9:42AM
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