I have been growing lettuce indoors with two different systems. One is a Kratky Mason jar and the other is a Kratky turned into DWC by adding an airstone.
I am growing Buttercrunch lettuce, which is a semi heading lettuce. It takes about 55 days to head up, although leaves can be harvested in about half that time.
So here is a video I made comparing the Kratky mason jar method to what started as a Kratky tote of lettuce.
I added an airstone, so I guess that makes it DWC or deep water culture.
Anyway, I am sure you can clearly see the difference an airstone can make.
The plant in the Kratky mason jar was started a week after the tote you see in the video.
It is pretty easy to see which plants are doing better, even though they are all Buttercrunch lettuce.
The only difference between these plants was adding an airstone and what a difference it makes.
Growing Lettuce Indoors With The Kratky Method
I’m not knocking the Kratky method. It works but for this particular plant because it’s a head lettuce, and it takes a little longer it doesn’t work that well.
It just about used up all the water, and it’s not done growing. Now for a faster growing plant like leaf lettuce it probably would work just fine.
Here are the roots, and they do look very healthy. So the Kratky method definitely works, and it really is a passive DWC system.
You are only supposed to fill up a Kratky container once at the start of a grow. Refilling it can cause problems because most roots are now air roots, and they can suffocate and rot.
If you really want to grow in a mason jar, they make 2 quart jars. They are a bit harder to find, but they also take a 3-inch net pot, just like the quart ones.
You can also use a gallon container and cut a hole in it for a three-inch net pot, and that would work really well.
But you can see that the roots are really healthy, so the Kratky method does work very well. You just need to size your container properly.
A Kratky With An Airstone Is Really DWC
So this tote started out as a Kratky grow. I had 12 lettuce plants in it. Six were leaf lettuce and six were Buttercrunch lettuce.
I realized that many plants might use up all the water in the tote. The tote holds 10 gallons filled to the top.
But it is only filled to the bottom of the net pots, so it probably holds about six to seven gallons.
So about a week in I decided to add an airstone. This would allow me to add more water and nutrients to the tote without damaging the roots.
Before I did that, I added a piece of polyester batting as a wick to each net pot. I don’t really think this is necessary
But I wanted to make sure that my plants had water until they could get roots down into the reservoir.
So far, I have topped up my tote one time with a couple of gallons of fresh nutrient solution. Here are the roots in my tote.
This tote got pretty crowded, so I harvested all my leaf lettuce and spread my Buttercrunch plants out in the tote.
Kratky Vs DWC Comparison
I mean, there’s really no comparison between the plant in the mason jar and the ones in the tote with an airstone.
So it is pretty obvious that if you want to grow lettuce indoors you should add an air stone.
The Buttercrunch in the tote looks good, excellent. Maybe the mason jar plant could have done better in a bigger container.
But even so it is half the size of the other plants and looks more than a week behind them.
Do You Want To Grow Lettuce Indoors?
If you want to grow lettuce indoors, you are better off using a tote like the 10 gallon Rubbermaid one I am using. It can be larger too, but probably not much smaller.
I used a 2 7/8 hole saw to cut 12 holes in the lid. You can put fewer holes if you want a wider spacing.
If you use a hole saw, use that size because anything larger and your 3-inch net pots will fall through.
But drill a 1/4-inch hole in the lid for an airline and add an airstone. Adding an airstone will make a heck of a lot of difference in your grow.
You know the Kratky method works well, but you have to have enough water in there because you’re not supposed to refill it.
Now, I did refill this jar a little, so I don’t know what’s going to happen to it. It should be okay.
I added about a half a container full of water back in with a bit of nutrients, and it should finish off just fine.
But honestly, this is a better system to use if you are living off the grid or in a Third World country where you don’t have electricity.
You know, an air pump doesn’t use that much power at all. So I would definitely add an air stone to my container.
If you are going to grow lettuce inside, I would do it in a tote like this. There’s really no comparison between the DWC and Kratky plants.
So I’m not knocking Kratky method. I mean, it works, but you have to have enough water to start because you only fill it up once.
So I don’t think it really works very well in a mason jar. It is just too small a container. At least not for a head lettuce, for a leaf lettuce you would probably have harvested it by now.
You know, if you really want to do the Kratky method, it does work. But the plant here should have gone into a one gallon container, not a quart mason jar.
Kratky or DWC Are Hydroponic Growing Systems
I grow with hydroponics because it means I don’t have to haul a lot of dirt around in my apartment.
All I need is a plant and a little bit of hydroton or something like that to anchor it in the net pot.
Add water and some nutrients and of course an airstone to a container and that will do it for you.
It is really easy-peasy once you give it a try.
Here is more info: