# Hydroponics in the cold! Late winter Hightunnel Greens.



## stanb999 (Jan 30, 2005)

There is very little information on cold weather hydroponics. I have tried to research this extensively with almost no results available. All sources suggest required low temps to be at least 60... but never less than 50, 40F solution is unheard of. What if I told you it can get to 33 or maybe even freeze a little? What if I told you temperature regulates growth speed just like plants in the ground as long as it's not below the freeze damage temperature. 

The test.. 
The beds are in my 30 x 50 ft mostly unheated hightunnel. 

The "heating"
I do heat to maintain above 20F in the hightunnel So the plants under row covers don't get killed by low temps. I have been doing this for a few years in early spring for the in ground plants so I can have full size greens by the first week in may. Basically I heat if the temp is forecast to go into the teens. My heating generally give a 10 degree boost. So if it's 15 outside it's 25 inside. Under the row cover it's 29 or 30F. If your not getting it... I let them freeze just not real cold. 


For the grow beds
I placed (3) 6" x 33" x 48" kratky style grow beds on the ground. Each with 24 plant locations. Each tank holds about 40 gallons of solution. 

Bed one I placed kale and swiss chard. 
Bed two I put boston bibb and romaine lettuces. 
Bed 3 is the same as bed one with the exception of 2 bok choy plants.

For fertilizer I used Chem-gro lettuce formula mixed per instructions.

The plants were started one week before in promix at warm 70F temps. They didn't get any special hardening off period.


Here is the plants on March 23 when placed into the tank. I have the boards there to help hold down the foam. The plastic liner was "puffing" it up.


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## stanb999 (Jan 30, 2005)

Here is the plants from yesterday afternoon. Monday was the first night I had to heat. The low outside was 12F the temperature in the hightunnel with heat was 22F with heavy frost. All the plants were under medium weight row covers. 

The growth so far... I will say the plants are growing well. They are going about twice as faster as the plants grown in the ground. But cold temps are definitely slowing them down. On a final note I may have lost the growing point on one of the kale plants. It's kinda black. The hydro bed is at the opposite end from the heater. Kale is also the most frost tender. It's just one on the outside edge of the tank. It could be that the tanks are covered with styrofoam and it keeps the ground "heat" in. :shrug: We will see if it recovers. The rest looked great. 

P.S. See the 8" of snow outside.


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## stanb999 (Jan 30, 2005)

The low everyday this week was below freezing. Mostly the hoop seemed to be about 25 in the morning. The lettuce, chard, and boy choy are doing better than those planted in the ground. The kale is lagging the in ground stuff, but it's coming along. This week is forecast to be good weather with lows near freezing. So I expect good growth. We will see. Here is the week 4 picture.


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## stanb999 (Jan 30, 2005)

This week the days where sunny so the Temps in the high tunnel where in the 70s. Nighttime lows are still at or below freezing. This week's pic demonstrates that the kratky system is best for bok choy hands down. The lettuce are twice the size of the ones in thesoil. The kale is still lagging those in the ground.


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## stanb999 (Jan 30, 2005)

Week 6, 42 days since planting. The lettuce and boc choy are ready for harvest and will be this weekend. The kale is big enough for a partial harvest we often just pic a few leaves from each plant weekly so we will see how long the harvest lasts. The chard is taking a while longer than we had hoped but it is better than the stuff in the ground.

The yield will be about 6 large heads of bok choy, 4 pounds of kale and 35 heads of lettuce at approx. 12oz.


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