Quick and Easy Mason Jar Hydroponic Setup

Want to try out hydroponics, but don’t want to spend much? Honestly it’s a big field with lots of complex terms and companies selling you the “next must have” item…. Let me help you create your first hydroponic setup without spending much, or maybe even without spending a single dollar!

Our goal is to create a “set and forget” system to grow lettuce.

The Supplies

The Container

Most people will do their first hydroponics with mason jars. They are such a versatile jar that pretty much every house has one, and they are cheap!

Photo of a mason jar.

If you haven’t got a mason jar, you can get this 34oz or 1L one from Ikea for $3.99, or this 1.9qt or 1.8L jar from Ikea for $4.99. Alternatively you could buy this 32oz double pack from Amazon for $8.

I personally recommend the largest jar possible; it’s more “set and forget”. Lettuce roots don’t need too much space to grow, but depending upon your environment and its growth rate you may find yourself adding water to a small jar every so often.

Hydroponic containers have to be opaque and black to stop algae growth… but you won’t find any mason jar like that. Instead, wrap the jar well with aluminium foil, or even paint a couple layers of black gesso or acrylic paint on the outside! If use chalk paint and you can later write or decorate your jars with chalk pens.

Week 1 Kratky Lettuce Compared
I painted these mason jars with two layers of black acrylic paint.

The Yoghurt Cup or Net Cup

If you have plenty of plants around your home, you may have a net cup already. They are often those little plastic cups with slots or holes in them that come with smaller plants. Make sure it fits. I use these 2″ wide-rim cups from CZ Garden.

Alternatively, you can recycle a plastic yoghurt cup. To be safe, please check What Plastic Should I use for Hydroponics? as not all plastics are safe to reuse. In the picture below you can see how I reused a sour cream cup:

Sour Cream/Yoghurt Cup Recycle for Mason Jar Kratky
Sour Cream/Yoghurt Cup Recycle for Mason Jar Kratky

The Nutrients

Plants will often get all their nutrients from the soil you plant them in, although sometimes you will add fertilizers or compost. Hydroponics removes the soil from the growing process, so you need to come up with an alternative way to feed the plants nutrients.

General Hydroponics Nutrient Combo Pack
General Hydroponics Nutrient Combo Pack

This is probably the only product that you may need to buy. If it’s your absolute first time attempting hydroponics you can probably get away with something like AeroGarden Liquid Nutrients (3 oz), though I would honestly encourage you to invest in a proper hydroponic solution like General Hydroponics Flora Grow, Bloom, Micro Combo Fertilizer set. This combo pack will last you a very long time, especially if you aren’t growing hydroponics seriously.

The Plant

Next you need to decide what plant you are going to grow: lettuce and basil are some of the most common plants for people to try for their first grow since they are fast growing, cheap and easy to manage. With the right setup you can even grow big plants like tomatoes (but they won’t grow in mason jars, sorry)!

GettyStewart has a great post about How to Regrow Romaine Lettuce from the Stem. She does point out that regrowing from a stem won’t produce leaves as large as store bought plants; and this probably has to do with the amounts of nutrients and lights that a store-bought plant receives compared to a stem in plain water.

I prefer to grow from seed; it has a fairly high success rate and only takes two to three weeks before I am harvesting. You can buy packs of various seeds fairly cheap, or individual packs from stores such as Botanical Interests.

If you live in Kuwait as well, you can read my post on where to buy organic seeds in Kuwait.

The Grow Medium

Hydroponics is mostly about removing the soil from growing plants, but you can’t just plop them into the water and hope for them to survive (some plants do, but most wont)!

You will need some form of grow medium. There are several different options with the easiest and most common being peat moss, rock wool and clay pebbles.

I regularly use Jiffy 7 Peat Pellets. They come in various sizes. Since the peat pellet is too small to fill up my entire DIY net cup, I pack clay pebbles around it. Alternatively you can use rock wool. You can simply cut up extra rock wool cubes to fill any spaces in your net cup. If you don’t want to cut up the extra rock wool, you can of course use clay pebbles as well.

It’s important to fill up the entire cup; we want to make sure that no light will get beyond the grow medium and into the mason jar.

The Light

Most people will put their mason jar and plant in the window, and generally there will be sufficient light for plant growth. Unfortunately my kitchen window is underneath a building overhang and thus gets very little light; so I need a grow light.

Buying grow lights is a bit more of a complex issue. I’ve written The Beginners Guide To Hydroponic Lights series that explore lights in detail in a very user-friendly manner. I’ve personally bought two different lamps: the Fissioning LED Grow Light and the Bozily LED Grow Light. Low strength beginner lights can be quite cheap; you may even be able to buy a normal bulb and relocate a lamp.

Build The Setup

(Optional) Paint Your Mason Jars

If you opted to paint your mason jars black, now is the time. Paint only the outside of the jar, remember that the paint itself is unlikely to be food-safe. Paint right up to the rim of the jar. Paint two to the three layers so that no light can leak inside.

Cut Your DIY Grow Cup

If you are using a recycled yoghurt cup, its time to cut some slits and holes in the bottom of the cup. Slits are generally better as they hold the grow medium without spilling, but still provide enough space for roots to grow through.

Sterilise Everything

Any non-living supply should be sterilised; jars, containers, and grow medium. The easiest way to do this is to submerge everything in hot water.

Prepare The Nutrients

In the post The Best Nutrients and Ratios for Hydroponics? I discuss how to measure out the General Hydroponics Flora Grow, Bloom, Micro Combo Fertilizer set. Since we are using a “set and forget” method, we need to use the nutrient ratio for vegetative growth. Mix 1 gallon, or 3790ml, of water with 3 teaspoons of FloraGro, 2 teaspoons of FloraMicro and 1 teaspoon of FloraBloom.

Fill your mason jar until the water level passes the bottom of the grow cup or yoghurt container by approximately .25″ or 1cm.

If you have excess water left over, you can water other plants with the mixture or store it to top up your lettuce water. You should not pour it down a drain! I store my excess nutrient mixes as I live in a dry climate and find water tends to evaporate faster than the plants are able to absorb.

Plant Your Seed

Make a small hole, usually about .25″ or 1cm deep, in your grow medium. Drop two to three seeds in and fluff grow material on top to cover lightly. Not all seeds with germinate, so it’s generally a good idea to put at least two seeds. If multiple sprout, you can always transplant or pull out the extra growth.

Place your grow medium in the centre of the cup, ensuring that the bottom of the grow medium is in contact with the water. Surround your grow medium with clay pebbles, or more rock wool.

Set and Forget

Place your mason jar somewhere bright, like a window.

Week 2 Kratky Lettuce Compared
Week 2 Kratky Lettuce Compared

And thats it! Over the next few days your plant should sprout. Some plants do take longer to sprout, so check your seed packet. My basil usually sprouts in about 5 days; at least you can see the tiniest of plants emerging around then.

Problem Solving

If your plant didn’t sprout:

  • You may need to wait longer; check on the seed packet for how long it takes for that variety of plant to sprout. Some species can take 20 or more days!
  • Make sure your grow medium is moist the entire time the seeds are sprouting; if you live in a very dry environment your water level may evaporate too fast for the seedlings to produce roots.
  • You could also have some bad seeds, try refilling your jar and planting more or new seeds.

If you notice your plants becoming wilted, chances are the water level is evaporating faster than they can absorb. Fill up your jar a little at the time! It’s very important to not fill the jar up the entire way; as the water level decreases the plant will grow water-roots and air-roots. If you submerge your air-roots in water your plant will literally drown. If you want to maintain your water level, I suggest the half-way point of the jar.

If your plant seems to be growing long leaves that aren’t very wide, you may not have enough light. Check out my post Do I Need Grow Lights? where I teach you how to measure the amount of light in your room.

Can You Germinate Seeds In Cloning Collars – The Experiment

I’ve seen some Youtube videos and articles where they grow their hydroponic plants in pool noodles. They claim to get high harvest yields, and they regularly talk about the benefit of being able to reuse the pool noodles.

Plastic Pool Noodles
Plastic Pool Noodles

I was concerned about the safety of using pool noodles; as we know plastic can leach chemicals and micro-particles into the water and plants (and eventually you). This process is often sped up with exposure to high temperatures… and Kuwait set a world record for the highest temperature in the world reaching 52.2°c (126°f) in the shadows and 63°c (126°f) in the direct sun!

Instead we bought a cloning collars and net cup pack as these have been specifically designed to grow plants and food.

After I bought the collars I realised that there weren’t many people online saying you could start seeds in the collars; they are generally used for transplanting cuttings from older plants.

I decided to do an experiment on whether I could grow seedlings in cloning collars.

I’m starting this experiment on Aug 7, 2019.

The Seed Added To The Cloning Collar
The Seed Added To The Cloning Collar

I sterilised the cloning collar and the container with hot water.

If you look closely you can see the Lemon Cucumber seed in the middle of the cloning collar. I’ve inserted it so its very close to the bottom of the collar (I’m holding it upside down), but far enough in that it hopefully doesn’t fall out.

My Test Grow Chamber
My Test Grow Chamber

Apparently seedlings will grow best when exposed to high levels of humidity. I wanted to make sure that my seedling could get as much light as possible at the same time. So I found this old Ikea air-tight plastic container. It has a de-gas spout which I have kept closed.

Fingers crossed that this container won’t grow algae since my nutrient rich water is also exposed to light.

Do I need grow lights? Update – Week 2

Read about the first week of growth in the post Do I Need Grow Lights? Update – Week 1.

It’s been two weeks since I transplanted my Deer Tongue Lettuce seedlings from the Aerogarden Bounty to my makeshift Kratky containers. The seeds were started in the Aerogarden on 17th July, so they are now only 18 days old. I started this experiment to test how the lettuce would grow under the light conditions of different rooms; my laundry, my pantry and my kitchen.

In the post Do I Need Grow Lights?, started just after transplanting my lettuce, I actually measured my light more scientifically. Spoiler alert, it was then that I discovered that my rooms were below the ideal levels for plant growth and that I would in fact need to purchase some grow lights.

Since my grow lights haven’t yet arrived, I decided to just let the lettuce sit in those rooms. Sometimes the amount of light to maintain is much less than the amount of light needed to create fresh growth. Even if the plants don’t get enough light in those rooms to actively grow, they may be acceptable places to store plants (if necessary) for a few days before I can completely harvest them.

Week 2 Kratky Lettuce Compared
From left to right: pantry, laundry, kitchen.

The lettuce didn’t really grow during this last week; the lettuce in the pantry being the exception. Compare this to last week:

Week 1 Kratky Lettuce Compared
Week 1 Kratky Lettuce Compared. Left to right: pantry, laundry and kitchen.

The pantry lettuce definitely grew a bit between week 1 and 2, although not as apparent in the photos. The leaves became wider and greener.

The laundry lettuce stayed mostly the same size. Its leaves did start to droop and curl slightly. This area is now being converted into a more permanent grow area including a couple nice grow lights!

The kitchen lettuce had started to die due to the lack of light. It struggled the most, which reflects our light readings that we got in the post Do I Need A Grow Light? The light was just so minimal in this area that the plant couldn’t even maintain it’s size, let alone grow! This area may be okay to store a plant in for a couple days, especially if the plant is destined to be eaten (why harvest all at once if I can pick the leaves off fresh over a couple days), but I won’t be trying to grow anymore in this area.

Despite hearing success stories online, I was a little skeptical if this method would actually work. But…

Photo of Lettuce Roots Growing
Photo of Lettuce Roots Growing

Seeing is believing! Roots emerged from the bottom of the DIY net cup, and quite proficiently. I was honestly quite surprised by the amount of root growth – only two weeks ago there were no roots at all touching the inside of the DIY net cup!

The End Of An Era

This experiment, the total of two grueling weeks, is now over. I’m moving what’s left of the lettuce to live under my new grow light; it’s now an experiment to see if I can get it to survive and recover.

How Long Should My Grow Lights Be On For Hydroponics?

I need sunlight daily to get Vitamin D, but if I get too much at once I will get sunburnt and potentially cancer! It’s better to get an optimal amount of light (such as when wearing sunscreen) over a couple hours.

Daily Light Integral

Just like us plants have optimal light brightness levels, as we calculated in the post How Bright Should My Hydroponics Light Be? Different stages of plant growth will require more or less light strength and lighting time. A seedling might need very low light strength over a short time (its a baby so it needs to sleep a lot), whereas a fruiting plant will need all the extra energy it can get through higher light strength and longer lighting times.

The best way to tell if your plants are receiving enough light to grow is by measuring the Daily Light Integral, or DLI. The DLI is a measure to of how many moles/m2/day our plants get. Notice how we will be converting from umols, or micromoles, to their higher unit. This is a bit like grams to kilograms, or ounces to pounds.

If you already have the PPFD or umols/s/m2, such as whats advertised when buying lights online, then you can use a simple online calculator to calculate your required number of hours to the DLI. If you don’t know how many umols/s/m2 your room or light is, check out the post How Bright Should My Lights Be?

According to Wikipedia having the correct DLI can help your plant leaves to grow thicker, increase flower and fruit yields, have more and stronger roots, as well as have more leaves and heavier biomass (they produce more leaves and less stems and stalks).

According to Specmeters:

DLI
Lettuce (butterhead)14-16
Tomatoes (seedlings) 6-8
Tomatoes22-30

Examples

I found a really great article from the Department of Horticulture and Crop Science: this PDF covers a huge variety of plants, and the recommended lighting and hours lit for each of the growth stages, and what level nutrient solution is ideal.

Lettuce

# Light HoursLight Intensity
(umols)
Propagation12-20150-250
Vegative12-20250-450
Flowering12-20250-450

Strawberries

# Light HoursLight Intensity
(umols)
Propagation12-20250-450
Vegative12-20 250-450
Flowering<12 250-450
Fruiting12-20 250-450

Tomatoes

# Light HoursLight Intensity
(umols)
Propagation12-20250-450
Vegative12-20450-700
Flowering12-20 450-700
Fruiting12-20 450-700

My kitchen had on average 250 LUX from the window – it’s a dark room considering direct sunlight has 900-2000umols. Using the Environmental Growth Chambers calculator, 250 LUX converts to 4.75 umols/s/m2.

If I was growing tomato seedlings, I would need to divide my result (4.75) by the number of hours to reach the ideal DLI of 8. In this case I would need my plants to receive approximately 1.5 hours of sunlight per day. An adult tomato needs 22-30DLI, so as it grows I would slowly increase the number of hours its exposed to sunlight to 6 hours a day.

But I will be using my grow light on my tomatoes. This light produces 565umol/s/m2. Using the same calculator I can tell that for seedlings I only need to expose them to 4 hours a day of light, whilst adult plants would need ideally 14 hours a day.

Quick Reference Chart

This PDF has a wonderful table of many, many, plants that compares different life stages, the strength of light recommended, and how many hours those plants require at such a stage.

Where To From Here?

Beginners Guide To Hydroponic Lighting has a list of all our posts on lighting, written to help a beginner learn the basics and get started right through to more advanced topics.

How Bright Should My Hydroponics Light Be? is the previous post in this series. It explores how much light certain plants needs to grow. I also show you how to convert to the more common used light measurement value umols or PPF, which many grow lights use. Understanding these values, and how they get them, will help you make an informed purchase.

Beginners Guide To Hydroponic Lighting

Wow! Learning about lights for hydroponics, or just plant growing, gets overwhelming fast. So many terms and numbers to keep track of. Here’s a roundup of posts that help explain lighting, all written for an absolute beginner in mind!

Do I Need Grow Lights?

Not everyone has a PAR meter or Quantum meter; they can be expensive. So how else can you measure the light your room gets? Whilst not very accurate, this can give you an idea of how bright your rooms are; helpful in finding out if you need to invest in a grow lamp!

How Bright Should My Hydroponic Lights Be?

This post explores how much light certain plants needs to grow. I also show you how to convert to the more common used light measurement value umols/m2/s or PPF, which many grow lights use. Understanding these values, and how they get them, will help you make an informed purchase.

How Long Should My Grow Lights Be On For Hydroponics?

So you know how bright your light should be, but how long should it shine? Plants need time to sleep and rest too, just like you. This post explores how to determine how many hours of light your plant needs (it can vary a little depending upon how bright your light is).

Grow light heights? Is it too close or too far away? – coming soon

Lights have different intensities, depending upon how far away you are to them. That little candle might not put off much light or heat from across the room, but up close you can still get burnt! This post will be exploring PAR, PPF and PPFD.

Waveforms and Colors – coming soon

Humans can see white light, and our eyes prefer it. But plants actually prefer different colors, most often reds and blues. This post explores the colors that lamps output – usually referred to in waveforms.

Do I Need Grow Lights?

Plants need light to grow, obviously. But what is the ideal amount of light? Honestly this question is quite debatable as growth is effected by the strength of light and how long the plants receive light.

I decided to test how much light each of my primary grow rooms are receiving; these are the rooms that I would like to ideally be growing herbs and vegetables indoors. I wanted to know if I could grow plants from the sunlight coming in, rather than buy a grow light. I measured the light amounts throughout the day, as the sun will shift and rooms that might get more light in the morning might receive very little in the afternoon and vice versa.

Lumens and Foot Candles

Warning in using this method

Measuring by lumens and foot candles are both considered widely inaccurate due to the different types of lights and the wavelengths light types each produce. Whilst we can see the light, plants need specific wavelengths to grow. Unfortunately most people don’t have fancy tools to measure the amount of light in their homes, such as a PAR meter or a quantum meter.

Even a rough idea of how much light your plants is getting is better than having no idea, so don’t get discouraged.

How To Measure

Thankfully, you can get a bunch of free apps on your phone that measure lumens easily and then with a bit of maths we can then convert the lumens value to the correct value, umol. I used an app on iOS called “Light Meter”. I did not buy the full version.

I like working in metric units – I just visualise meters easier than feet. Lumens are a metric unit, whereas foot candles are imperial. If you want to convert between the two:

1 foot-candle is equal to 10.76 lux, and this is derived from 1 lumen/square meter = 1 lumen/10.76 square feet. (One square meter = 10.76 square feet).

Minimum Lumens Needed

It was really hard to find this information, since everyone agrees that lumens are not an ideal way to measure light for plants. Furthermore, when most people talk about lights and plants, they will use the measrument unit umols/m2/s or PPF. The post How Bright Should My Hydroponics Light Be? goes much more into depth about what plants need what level of light.

None-the-less, this post is to help you know if you potentially need a grow light. So at a very quick glance at the tables below you should be able to tell if your plants may survive in their current lighting setup.

According to PlantMaid website,

LUX
Low Light Plants500-2500
Medium Light Plants2500-10,000
Bright Light Plants10,000-20,000
Very Bright Light Plants20,000-50,00

Even LumiGrowth website says that plants ideally need 3230-8610lumens/m2 in order to grow.

Obviously these values will all vary depending upon the size of the plant, its life stage (vegative vs fruiting) and the type of plant. Again, check out How Bright Should My Hydroponics Light Be? as this post has much more detail.

My Own Measurements

Kitchen

The following light measurements were taken in my kitchen. I have two locations where I tend to want to keep plants; in the back corner on counters that are rarely used, and underneath the window.

9am12pm3pm6pmAverage LUX
Near Window75232292258214
In CornerLess than 10Less than 101002033

I was honestly surprised that the back corner of the kitchen got so little light. I knew that the kitchen could get quite dark, but the ambient light didn’t seem that dark during the day. This could explain why many of the plants I put in the back corner would keep dying as they were receiving so little light. I thought I just had the opposite of a green thumb…

I was surprised to see that the Kitchen Window (214) received more light than the Laundry (167) overall, as I thought that this area was darker since there is a building overhang. Given this information I may buy a shelf that I can install near the window.

Pantry

The pantry receives the most natural light out of all my “grow rooms”. The room just seems to be ideally faced (at least in summer) to receive bright light throughout the entire day.

Official Photo of Aerogarden Bounty
Official Photo of Aerogarden Bounty

Its also in this room that we have our Aerogarden Bount models currently set up. I took light measurements with the Aerogarden lights both on and off, as the machines will regulate for their specific plants, but light will overflow to the rest of the room when running. The pantry has multiple shelves where plants can be placed, so I measured whilst standing in the centre of the room at equal distance between all shelves. This room does have a window, so one wall will certainly have much more light than others.

9am12pm3pm6pmAverage Lux
Aerogarden On294315243148250
Aerogarden Off27531517273209

Laundry

Unlike most people, we have an indoor laundry. We get too much dust in Kuwait to realistically hang our clothes outside; so we have a washing machine and fold out line installed in a “small” room. It’s a bit like a mud-room. The laundry will be our primary grow room, at least for larger plants such as tomatoes. Its not as highly accessed as other rooms, so the plants will go undisturbed. And the room tends to be slightly more humid than other rooms.

We already know that this is one of our darkest rooms. The window is very small and doesn’t seem to receive much natural light. We are planning to put a grow light in this room in a few days, but we are testing to see how it performs without.

9am12pm3pm6pmAverage LUX
Laundry150235173109167

What Did We Learn

After measuring the light intensity in all my ideal rooms, I have learnt that none of the rooms have enough light to grow any plants. The brightest area was 250 lux, and unfortunately low light plants will need at least 500 lux. So it seems that for me to grow any plants indoors I will need to invest in a couple of grow lights.

Where To From Here?

Beginners Guide To Hydroponic Lighting has a list of all our posts on lighting, written to help a beginner learn the basics and get started right through to more advanced topics.

The post How Bright Should My Hydroponics Light Be? is the next step in this series. It explores how much light certain plants needs to grow. I also show you how to convert to the more common used light measurement value umols or PPF, which many grow lights use. Understanding these values, and how they get them, will help you make an informed purchase.