Backyard Aquaponics
A place to discuss aquaponics

So, I got rid of the arugula I had over winter because it was outrageously bitter. These were from seed I cultivated from a soil plant on my patio. The soil plant was the perfect flavor.

To fill that space, I put in a lettuce blend (mesclun maybe). The seedlings started popping up in late January.

My system is inside near a window. We are in Boulder. We had some very cold weather and I made sure to get heaters for the fish to stabilize the water temp. 3 of my girls had eggs in February, but none of them survived (I'm a newbie - especially to babies)

Now, in March, Spring is just starting here in Colorado. I wanted to have some of the lettuce, but it tastes like crap! This same blend that I've had from soil (outside, last spring/summer) and was fantastic, is just awful from my aquaponics system.

It is definitely not heat, but that is the only explanation other forums have given people with bitter lettuce. The plants are about 100 days old. I doubt that is old enough to be as bitter as they are.

In February, an expert told me that if my plants are spindly that I may need to add potassium. They were spindly (overly tall, falling over, not bushy like the soil ones were). But they've grown out and look good - not amazing, but good.

Could a lack of potassium also cause bitterness?

Apparently lack of moisture, stress, slow growth, nutrient levels, and getting near bolting can also contribute. Any information on the Nitrate levels?

What type of lettuce is this?

Try soaking the lettuce for an hour, then wash and dry. Store in the fridge for a couple of days before use and see if they've lost at least some of their bitterness (doesn't always work but it may).

Some Hydroponics growers grow then in water for the last week before harvest to ensure that the nutrients don't cause the lettuce to be bitter.

Great tip!

Do you have extra lighting on the plants inside? If they are spindly, it sounds like they are leggy, which can make them bolt earlym and bolting lettuce is bitter.

Otherwise some varieties are bitter, and if you collected seeds, they might have crossed with another lettuce to make a bitter lettuce?

yep, definitely sounds like they have already bolted to me, spindly and tall.
The only other ways i would normally see overly tall lettuce is if you planted way too many way too close together, but wouldnt be bitter.

What Nitrate level does the system have?... I've noticed with Lettuce that once my Nitrate level exceeded 40ppm they started to become bitter, and once it hit 80ppm they were extremely bitter.

I'm not sure if it was actually the Nitrates causing the bitterness. The high Nitrate level is a reasonably good indicator that other nutrients also be in high in the system, it could well have been a high level of another nutrient.

As far as bolting is concerned I've found it's usually one of two reasons, excessive humidity or heat, or lack of light.

I also grow indoors under lights and currently have a brilliant example of lack of light causing a lettuce to bolt. I have a number of Oakleaf Green Lettuce seedlings from the same batch spread across a 1.2m x 1.0m GB, the closer they are to being directly under the light, the more compact they are. Those out on the edge of the GB are bolting.

Bolting Lettuce as mentioned above:

Hey can anybody else confirm that high nitrate levels may cause bitterness in lettuce?

I currently have the same problem about bitter lettuce and my nitrate level is at 100 ppm.

Harvested my lettuce 32 days from transplant and its bitter. Thought maybe it was because I harvested too late.

Not much out there and I don't know if I was searching for the right terms. It's not the most common cause but here are a couple of sources that indicate Nitrate is linked to bitterness -

I don't know if this will post correctly but this source says that "Bitterness in lettuce has been linked to Nitrate accumulation in the foliage" - https://books.google.com/books?id=Wzgh9qy30KIC&pg=PA96&lpg=PA96&dq=bitter+lettuce+nitrate+levels&source=bl&ots=MN0Xqx339R&sig=6WJm87XjvQ66F67fSHuqKbEkLfs&hl=en&sa=X&ei=hD0cVd-CEsvsoASntoFY&ved=0CDEQ6AEwAg#v=onepage&q=bitter%20lettuce%20nitrate%20levels&f=false

Should see this on p 96 of the book if it doesn't go there with the link.

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http://homeguides.sfgate.com/reduce-nitrates-hydroponic-lettuce-76309.html

Thanks for that Scotty435. The link you gave me also mentioned about hot temperature. I think that is what primarily happened to me. My root temp went from 27 to 29.6 deg Celsius and the ambient temp went from 30 to 38 deg celsius. I would be in a bad taste too if I were my plants....

@ Ronald:


I think lettuce may be hard for you, would need input from cookie, dasboot, etc.
your water temps may always be too high in the phillipines, they tend to be winter vegetables here in melbourne, rathering soils temps below about 20c i think, as thats about all soil usually gets to.

http://www.weekendgardener.net/vegetables/lettuce.htm

Hi Ronald,Yavimaya is right with those temps you are going to struggle with a lot of plants,if there is anyway you you can keep the water temp down they will last longer before bolting,there are papers on the interweb where they did growth checks against temps,the outcome was that if you are lucky enough to keep the water temp down to 18/20c they will survive air temps nearly up to 30c without bolting.
As a bi line i am having success with Butterhead and Greenoak lettuce,but my water temps are only 22c,air temp in the tunnel 35c,Grand Rapids gave up a while back,Toms are about to give up as well.

@Yavi and Dasboot

Yes, I know I put myself in for a challenge when I decided to do "lowland" lettuce using aquaponics in an urban setting. Plus commercial targets.

But, seeing as everything is more expensive to do in a city I don't think it would be cost effective for me to raise anything but high value crops.

I haven't given up yet on cooling my water. Currently, I just finished converting an old window AC into a water chiller. I'll give it a few days to try and see if it will help. I'm still playing around with other ideas as well.

Frankly, in the end, I feel like I will have no choice but to compromise a little... maybe I could get my system to work with lettuce but NOT in summer...

Is lettuce high value over there?

surely there are other crops which arent hugely available that would do well in AP? fruiting crops? Pepinos perhaps.

Yes lettuce is high value in this part of the world because its a cool crop while our temps generally is hot.

Pepino on the other hand is very cheap here. He he.

If you and I had a matter transformer we would strike it rich!