While I am an avid gardener outdoors and in my greenhouse, I've always shied away from trying any type of hydroponics, simply because they always looked a bit complicated and expensive. However, recently I was introduced to something called Passive Hydroponics (a.k.a. The Kratky Method) which requires no elaborate setup, no running water, no pump, no aerator and very little brains , and can be done in something as small as a 1 quart Ball Canning Jar.

I love fresh lettuce, spinach and herbs for my salads which I eat year round. This time of year, with the hotter weather, it gets more difficult to grow lettuce and spinach, and it bolts very quickly. So, I've decided to set up an indoor passive hydroponics "system". I already have some of the supplies I need (Ball jars, grow lights) and I have ordered the rest (nutrients, net posts, clay pellets and a wire shelving unit).

Here's a brief video that demonstrates this method:



Here is a list of the needed supplies:

1. A 3 or 4-foot-wide baker's rack.

2. Wide mouth quart size canning jars.

3. 3-inch diameter net pots to place into your canning jars to hold your plants.

4. Hydroponic clay pellets.

5. Hydroponics nutrients can be in either powdered or liquid form.

6. A 24-hour timer.

7. Water.

8. Seeds.

9. A one-gallon watering container to mix the nutrients.

10. Dark socks to put around the jars to block the light to the roots.

11. One high quality LED Grow light that will provide even lighting over a 3 foot by 18-
inch area of the shelf for each shelf you plan to use.

So, I am going to be starting this shortly, and I will post about it here. If you are familiar with this method of hydroponics, or want to learn more, I hope you will post. The more, the merrier!

Interesting way of gardening.

Can't wait to learn more about this.

It's been a couple of weeks since I started this thread. All my supplies are in, but I've been so busy I keep pushing off setting up my hydroponics experiment. I'm hoping to get it set up today!

I am a member of the Hydroponics Plant Growth group on Facebook sponsored by Happy Leaf LED Grow Lights, and one of the members just produced and posted a 9 video series on YouTube that walks you through everything from soup to nuts in growing lettuce hydroponically using the Kratky Method. All the steps to grow lettuce are shown, from the setup of the grow area, to the harvest of lettuce.

This is the URL to the entire series: https://youtu.be/sAHpUnrOJnQ?l...

Day One

Finally got my hydroponics experiment set up today. I am starting with 3 jars with White Paris Romaine seeds. I have to level off the shelf. I live in an old farm house built in 1840. Nothing is level in this place!

Can't wait to see how it goes

Day 3. Yesterday I noticed a small white root beginning to emerge from a few of my seeds. This morning I awoke to a few of them actually starting to put out very tiny green leaves. It's hard to see from this picture (my camera does not do well when so close to a subject). Here is a pic of one of the jars.

I have been doing Kratky for about 8 months. Have had great success, especially with greens. All done inside under grow lights. Lettuce has done great, and have done several rounds of it. Takes about a month from seed to harvest, and I do "cut and come again" so it lasts a long time. Look that up if you don't know what it is.
See the pictures below. One lettuce pic is when it was very young. It gets much bigger. Another pic is my hand for size comparison over some heads that are almost ready to start harvesting. A few more days to go. Some leaves are almost as big as my hand eventually. You can see the root growth on some other plants in a container. The roots are brown because those particular lettuce heads were old and almost spent. White when younger. I have even had success with a Husky Cherry tomato plant, believe it or not (indoors!). It has about 20 tomatoes on it right now, with lots of blooms still forming. I have already harvested a few. I have a t5 fixture suspended above and a long fixture hanging vertically next to the tomato.
We have to give lettuce to the neighbors because I am cranking it out so fast! (Romaine, giant Caesar, black seed Simpson). Oh, have also done Malabar spinach.

Hi @Murphy11,

Glad to have found someone who is doing Kratky! All of your plants look great. I decided to start off with lettuce in Ball jars to experiment with, but I also want to do spinach, herbs and perhaps even tomatoes. At some point I will probably move to buckets or Rubbermaid Totes. I am using a Happy Leaf LED Grow Light (https://happyleafled.com/). I've been using them for a few years in my greenhouse. For nutrients I am using MasterBlend (https://www.amazon.com/dp/B072F2BL9D/). One thing I already like about growing this way is no soil mix in the house!

Jim

Well, I would wish you luck with your hydroponics, but once you have it figured out... you won't need much luck! It's easy and a lot of fun. Like you said, no soil in the house. No variations in temperature, wind, rain like being outside. No outdoor bugs or pests to worry about. I have had no flies or bugs etc indoors with this. It's clean and tidy and no earthy smell from potting mix to smell up the room. I basically cleared out a closet and turned it into my grow room. I thought it would be harder, but it turned out simple.

I watched lots of YouTube videos, and then trial & error from there. I started trying to do lettuce in solo cups, and it wasn't bad. Did some mason jars. It grew in every container. But, the three problems were root space and nutrient volume and maintenance.
Once the plant achieved a little size the nutrient solution would run dry in a day, so I was constantly refilling. But you can only refill a little so as to not drown the roots. So the refill doesn't last. Became labor intensive. As always the plant grows larger if it has larger roots, and the cups and jars restricted root size. Also, you have to think about how you will check roots and refill. On several occasions I broke the lettuce head off the root when I was trying to lift it up to see the nutrient level. It was clumsy and cumbersome.

Once I moved to the larger containers the lettuce heads just exploded. I'm using these plastic bins that are about 15 inches long and about 7 or 8 inches deep I think. You can also get a rough idea from my pictures. I can safely get four plants into one of these boxes. I still have to refill but only very little and towards the end of the plant's life anyway.

Cut holes in the top with a hole saw. You know, just like all the YouTube videos.
Look at the picture of my tomato plant's box. Those are orange pool noodle pieces about an inch thick. I wedge them into the top opening of a solo cup. Cut out the bottom of the cups leaving about 1 to 2 inches deep from the top. Then they fit perfect into the opening. You can also see the red solo cups in the root picture.

Of course to do this I had to grow seedlings in regular soil type seed starting mix. Then carefully remove the seedling and rinse the roots off, and then place them in the center hole of the pool noodle and use another small piece of plastic or pool noodle to gently wedge the seedling in place so it is suspended above the nutrient solution with the root submerged. Sorry I don't have pictures from this process.
The plants basically reached full maturity and beyond with no further intervention, until I started harvesting. Then maybe a small refill or two towards the end of it's life.

Basically I did the whole thing without buying any net cups, rock wool, clay pebbles, etc. all DIY with household products and a pool noodle. Of course I use a legit nutrient solution mix. Can't remember the name of mine. But the masterblend is a common brand I hear of a lot.

I also have two tomato plants outside in larger Rubbermaid totes.

Overall it has been a lot of fun and you get quick results in just a few weeks. And if you get a rotation going you always have a new young box growing, a box right at maturity, and an old one reaching the end of it's life. More lettuce than you can eat.

I cut leaves off a few times a week and store in the fridge, or just cut them and eat immediately as needed.

Well, I have rambled enough. I hope this helps. It's a great experiment and learning process. Have fun. Let me know if you have questions and I will try to help.

Here are a couple of additional pics. I made one setup with a piece of cardboard instead of cutting up a lid. On that one you can see I use little applesauce cups and rocks out of the yard. Here is some of my lettuce in solo cups too.

Wow, I really like the way you have done all this without buying a lot of the "standard" equipment you see online and in so many videos...apple sauce cups, front yard rocks, pool noodle pieces, etc.

I already had the Ball Jars and LED grow light, but I did buy the net cups and clay pebbles. I'll use them since I already purchased them, but I could have saved a few bucks.

I also am amazed at how much you have accomplished in such a short period of time. Great idea using a closet, but it is one thing we are in short supply in this old 1840's farmhouse we live in...not sure why they didn't build more closets back then.

I am already thinking of adapting some of this method to my greenhouse next spring.

Thanks for the offer of help; I'm sure I'll have questions as I go forward, and keep posting those great pics!

Day 7



Easier to see if I turn the light off to take the picture

Interesting, Jim. Why do they have the coverings?

The coverings are old black cotton socks. The purpose is to block the light from the water so it doesn't grow algae which would be detrimental to the plant roots. You can use anything to cover the jars as long as it blocks the light. Some folks paint the jars black. Of course, you can also spend money to buy covers for the jars, but why spend the extra money.

Many youtube videos show painting the container black. Using black socks like MoonShadows is perfectly fine. I have had pretty good luck with wrapping containers in newspaper, but have to use enough layers to make sure the light is fully blocked. We get a daily newspaper so I have all the materials I need. Of course if you are buying a larger plastic box or tote, just find ones that are not clear.

The Romaine is looking strong! Keep up the good work.

Okay. You sold me. I just happen to have a set of four-foot LED grow lights still in the box that someone didn't need and gave me. And a rack and a space on the enclosed porch for it. Settling on containers now.

IntheHotofTexas said:Okay. You sold me. I just happen to have a set of four-foot LED grow lights still in the box that someone didn't need and gave me. And a rack and a space on the enclosed porch for it. Settling on containers now.

Great!

I just took a look at the pic I posted above yesterday, and I am amazed at the growth in the past 24 hours.

I also set up 3 more jars.

So, a couple of questions.

You are using 32 ounce jars for some. How often do you find they to have water/nutrient added for, say, a large sort of lettuce or kale? Any benefit or pro/con for a one-time filled bigger container versus topping up a small container?

You fill them back up with the same as the initial mix?

When you finally harvest a jar, can you just top off and reuse the same solution? Any limit on that, or does the water just eventually get nasty?

I see you don't use things like seed sponges. Does it work okay just seeding the clay pellets directly? Do you have to make sure the liquid begins up at the level you drop the seeds, of does the clay wick at all?

Any comment on the difference between using jars and using much larger buckets and containers holding multiple cups? Do you feel your plants get a large either way?

Also, I am going to put a rack on a semi-enclosed back porch. One side is a house wall, one is a glass wall, the third glass wall sliding doors, and the fourth screen windows with louvers. How important is the ambient temperature? It would never freeze, but in parts of winter, it certainly would get much colder than an inside room or a basement would get.

Jars seem to offer a lot of versatility for the small grower, things like shuffling jars between shelves to keep the lights right height. I saw someone, I think Indian, being very frugal and using a found big plastic bowl and just some sort of rescued plastic laid on top with holes and cops.

Since I just started doing this, I haven't had to fill a jar, yet. My understanding is the nutrient mix in the jar can last the whole life of the plant (lettuce in my case). As the lettuce grows, it begins using up the nutrient mix. Some of the roots stay in the water as it recedes, and some are exposed to the air in the jar which is important because the roots need to be exposed to oxygen, too. If the nutrient level gets low, you can always add more, but do not cover all the roots (fill up to the top again) or you will starve the roots of oxygen and the plant will die.

From what I have read, the jar should be cleaned and fresh solution used for each new planting.

When I started, I filled the jar right up to the ridge line below the top (see video in the first post of this thread). When I put in the net cup with the clay pellets, the water rose to the level of the top clay pellets, but did not cover them. A couple of the seeds were actually floating in a bit of water, some landed on the moist pellets. Both sprouted. Remember, the water level will begin to go down somewhat just from evaporation.

I started with jars as I wanted to just try this method out before committing to it. I imagine I will move, at some point, to larger tubs or buckets where I can grow more plants in a single solution reservoir.

The ideal temperature for this type of hydroponics is 68-72. That is why it is ideal for doing indoors. Lower temperatures will not hurt the plants, but the growth will slow down as the temperature drops.

I have 3 shelves on my rack. If I remember correctly, I spaced them 20, 24 and 28 inches. However, I also hung my lights using shoestrings and those little toggle spring clasps, so I can easily raise or lower my lights as needed.

Toggle spring clasps