Lettuce growing tall?

[Matt T.]

I have an IBC system with Simpsons Elite lettuce, pac choi, shard, and red oakleaf. I have noticed the lettuces growing taller than they should. Almost as if either there wasn't enough light, or maybe bolting without the seed heads forming. I have a 250 watt metal halide bulb place 24 inches directly above. I can feel a little heat when my hand is at the top of the plants. My water temp is at 75°.  Any ideas on if it is to little light, or to much heat? I am figurig there are no seed heads developed because of the blue spectrum of light using MH bulbs, but I may be over speculating on this?

[BenHehle Beamz]

Lettuce bolting mostly occurs due to high temperature. It always depends on the variety you grow. Most of the common garden salad (head salad)  Lactuca sativa, forms a big compact head. If the temperature is too high, or in some cases, in absence of nutrients, you will see a non-compact formation of single, bolting, long stemy leaves. Ideal temperature for lettuce is 60 to 65F. If the temperature gets close to 80F, they will start to bolt. Hang the lamp up higher and give some new seedlings a try.

[Matt T.]

I dropped the temp by 2°, from 75° to 73° over several days. My bluegills have all but stopped eating for reasons unknown to me. As for the lettuce, it is not sending up seed/flower stalks, which would confirm the bolting. I'm still waiting for the seedlings to get bigger before I introduce them to the system. After that I'll take out some of the tall lettuce to allow more light. Taking too much lettuce out now will cause my nitrates to climb to high, and who knows what else....

BenHehle Beamz said:

Lettuce bolting mostly occurs due to high temperature. It always depends on the variety you grow. Most of the common garden salad (head salad)  Lactuca sativa, forms a big compact head. If the temperature is too high, or in some cases, in absence of nutrients, you will see a non-compact formation of single, bolting, long stemy leaves. Ideal temperature for lettuce is 60 to 65F. If the temperature gets close to 80F, they will start to bolt. Hang the lamp up higher and give some new seedlings a try.

[Pat James]

Matt, you have water temps of over 70 degrees now in Wisconsin? Is this indoors? I live in Louisiana and the highest my water temps have been lately is 61, and that was a pne time reading.

[Matt T.]

I have it set up in my basement. I'm worried the bacteria won't keep up. I also need to add another GB, so I'm starting a small raft tank. I just found the temps for bacteria in Sylvias book, and The growth will only decrease by 50% at 64 degrees. The fish not eating is a concern though. I posted on that in the Fish forums. This is my first set up, and I only lost one gill in 3 months.

[Alex Veidel]

The issue is too much light. I've found that excess lighting caused my lettuce to get really long stems, and I even had spinach that went straight to bolt. How many hours per day are you giving?

[BenHehle Beamz]

Dont worry about the water temperature, thats not the reason why your seedlings are bolting. You said that you have a 250 watt metal halide bulb place 24 inches directly above. Thats why your lettuce is bolting. When i mentioned 60-65F, its refer to the air temperature not water temperature. Hang the light up higher and give your crops less light (length). Lettuce is a long day plant. Its a guess, the length is around 9-12 hours. Keep it around that. Well, just give it a try.

[Matt T.]

I just raised my light, and turned the timer down to 12 hours on. I'll be putting in some new lettuce sprouts this weekend, and will take the overgrown ones out one at a time over several days so my nitrates don't climb to high. Thanks you guys!