Semi Hydroponics 101: Growing Plants Passively Without Soil

If you love houseplants, but find them difficult to care for, or the soil too messy to deal with indoors, semi hydroponics could be the solution you didn’t even know you were searching for.

With semi hydroponics, you can easily convert most houseplants into “semi-ponic” plants, which are easier to maintain and do away with soil completely.

What is semi hydroponics?

Semi Hydroponics, also known as semi-hydro, semi-ponics, or LECA, is a growing technique that involves replacing soil with inorganic mediums such as clay balls, LECA, and other absorbent mediums typically found in hydroponic growing systems. Converting plants from soil to semi-hydro is a growing trend among houseplant enthusiasts.

Read on below to find out more about semi hydroponics and exactly how it works.

How Semi Hydroponics Works

Semi hydroponics is a passive growing method that lets you take regular household plants and convert them into easier to care-for plants without the need for soil. 

Semi hydroponic plants, as plants growing with this technique are often referred to, are set into “double” containers. One container holds inorganic materials that both help absorb water as well as anchor the plant into place.

The second container acts as a reservoir like typically found in hydroponic systems. The two containers fit together like a glove and are connected by small drain holes in the bottom of the top container.

When the plants are watered, they absorb what they need and the rest of the water drains into the second container. Roots from the plants may work as wicks, sucking water up from the reserve as needed.

If set up properly, and well-maintained, semi-ponic plants are extremely easy to care for.

Further, root rot, pests, and soil-based bacteria and diseases are drastically reduced. 

Semi Hydroponic Pots & Containers 

The best pots and containers for semi hydroponics are self-watering. You’ve probably seen them at the local department store’s gardening section, or online while browsing Amazon.

A great container for semi hydroponics is one that allows enough space for your chosen plant, but also allows for at the very least a shallow reservoir in a second lower section of the container.

These are the pots I’m using for my houseplants and they’re working great.

Semi Hydroponic Net Pot Set

You can pick them up on Amazon right here.

The nursery pots you bring plants home in can even be placed inside a cache pot filled with nutrient water for a cheap alternative.

In fact, many semi hydroponic fans enjoy the DIY aspect of creating their own pots and containers. The options are endless.

Semi Hydroponic Mediums

There are numerous growing mediums that work well for semi-hydroponics. That said, they all share similar characteristics; they are inorganic, absorbent, and typically reserved for hydroponics.

A few popular choices are:

  • LECA / Clay balls (I’m currently using these)
  • Pumice
  • Loose gravel
  • River rock
  • Sand
  • Foam
  • Rockwool
  • Vermiculite
  • Perlite
  • Other soilless mixes

Can Any Plant Grow in LECA?

Lightweight expanded clay aggregate, or LECA for short, is the perfect medium for semi-hydroponics, as most plants are capable of growing in it.

LECA is also the most recommended medium for semi hydroponics. That’s why many semi-hydroponic gardeners call the growing method itself LECA.

Nearly all plants grow well in LECA after adjusting. The only difference is that some plants require watering less, while others need water more often. But, it is the same when using soil, so there is no real downside.

Watering Semi Hydroponic Plants

Most plants require watering no more than once every two to three weeks once converted to semi hydroponics. There are always exceptions of course, as there are with any growing methods.

Some plants will always need watering more than others, regardless of their growing medium.

Generally speaking, plants that are grown with semi hydroponics can go as much as two to three times as long between watering as the same plants that are grown in soil.

Semi Hydroponic Fertilizer and Nutrients

One big difference between soil-grown plants and those grown with semi hydroponic techniques is that semi-hydro plants need fertilizer and/or nutrients

In soil and solid fertilizers, plants are able to leach all the nutrients they need. Replacing their growing medium with LECA or clay balls means you’ll need to make up for missing nutrients.

The best way to introduce nutrients into your semi hydroponic setup is into the water you feed them with. You can also add your liquid nutrients into the reservoir and let the plants wick them up as needed.

Semi Hydroponics plants require the same macronutrients that hydroponic plants do:

  • Nitrogen
  • Potassium
  • Phosphorus
  • Calcium
  • Magnesium

They also need some micronutrients:

  • Sulphur
  • Iron
  • Manganese
  • Copper
  • Zinc
  • Molybdate
  • Boron
  • Chlorine 

When I first started converting my soil-based houseplants to passive hydro, I found this video super helpful in explaining nutrients, pH, and exactly what’s needed.

Semi Hydroponics vs. Soil 

The differences between using semi hydroponics and growing plants in soil are massive. Soil comes with pests, bacteria, diseases, messes, and needs watering much more frequently than semi hydroponics.

Further, soil only lasts for so long and needs to be fertilized, recycled, or completely replaced altogether. With Semi-ponics, the inorganic medium lasts much longer and simply requires cleaning from time to time.

All things considered, semi hydroponics is an easier way to grow plants than growing them in soil, period. That includes planting them, propagating them, maintaining them, and watering them.

Semi Hydroponics vs Hydroponics

Hydroponics is an excellent way to grow plants, but it is not nearly as convenient as semi hydroponics for houseplants, flowers, and herbs. 

Why not? Well, there are several reasons:

  • Hydroponics takes up more space and takes more time
  • Water pumps, air pumps, and other components are needed with hydroponics
  • Hydroponics requires a lot more maintenance and monitoring
  • Your electricity bill is higher from hydroponics
  • There is a larger learning curve for hydroponics

Semi hydroponics is easier, takes less money, components, and experience than hydroponics. It also saves you space and time in comparison to the latter. 

Semi Hydroponics Pros & Cons

Pros of Semi Hydroponics Cons of Semi Hydroponics
  • Anyone can learn
  • Requires less water
  • Easy to convert plants from soil to semi-ponics
  • Cost less than hydroponics
  • Takes less time to care for than soil, hydroponics, and other grow methods
  • Plants are free to drink and feed as they need
  • No mess from soil
  • No complicated components
  • Plants require nutrients or fertilizer
  • Plants may go into shock while being converted to semi-ponics
  • There are a few initial costs to converting from soil to semi-ponics

Best Plants To Grow Using Semi Hydroponic Method

Technically speaking just about any plant that grows indoors can also be grown using the semi hydroponic method. However, some plants are far easier to convert to semi-ponics than others.

Among the best plants to grow with semi hydroponic techniques are:

How-To: Converting Plants To Semi Hydroponics

Getting started with semi hydroponics is not nearly as hard as it may seem. Once you get going you’ll wonder why you waited so long to get started.

Supplies needed:

1. Remove Plant From Existing Container and Clean Off Soil

To start, get over an old plastic tote/trash can, remove the plant from its current container, and gently begin to dislodge and shake free the dirt.

2. Rinse Plant’s Roots

Once you’ve removed all of the dirt that you can, thoroughly rinse the roots off in the water.

TIP: I recommend doing this outside, if possible, so you don’t clog your sink.

Be sure to get all of the organic matter (soil, peat, bark…) out of the roots – it’ll cause problems if you don’t.

It’s normal for a few roots to break off during this step, but be as careful as possible.

When you’re finished, the roots should be mainly white. If the roots are yellowish or brown, check them for firmness. If they are smooshy, they may have root rot and shouldn’t be repotted.

3. Rinse and Prepare New Medium and Pots

Stick your plant into a glass or mason jar filled with clean water and allow it to soak for a few more minutes. During this time prepare the new medium (hydroton/leca) by rinsing it out in the sink or bucket.

Rinse until the water runs clear. (Again, I recommend rinsing outdoors to keep the clay dust out of your drains.

Only after you clean the new containers with soapy water and dry them out should you add the new medium. Once these tasks are completed it’s time to move on.

Place ⅓ to half of your medium into the smaller pot with holes in its bottom, and set it inside the larger solid pot.

4. Prepare Your Nutrient Water and Test It

I use these hydroponic nutrients from General Hydroponics. Follow the instructions on the back label to make your nutrient water.

I started my plants with 1ml of each nutrient per gallon of water. I also use distilled water.

You can increase over time as your plants get used to things. Again, I recommend checking out this video on semi-hydro nutrients.

5. Check and Adjust pH as Needed

It’s time to test the pH of your nutrients. Grab your pH test strips and pH adjuster.

Follow the instructions for testing your water.

Generally speaking, the pH should be 5.5 to 6.0. 

But, there are tons of exceptions so make sure you know the correct pH level for the species you are growing.

If the pH level is not as balanced as it should be, correct it immediately by adding pH UP or pH DOWN.

Keep testing the water each time you adjust it. 

6. Transfer Plant to New Medium

With the new pots ready, gently remove your plant from its jar of water and spread its roots out. Place it into the container with its main roots each going in separate directions. Make sure the roots are spaced out as much as possible.

Slowly and carefully fill the rest of the container up with the new growing medium. When your plant is well-anchored, you’re finished with this step.

7. Water Plant and Top off Reservoir Regularly

After your liquid nutrients are mixed and added to water, feed your plant for the first time. 

You should hear the water leaking from the drainage holes and into the larger solid container. When you no longer hear this, you know the reservoir is full.

You want the water to be 1/3 of the way up the net pot. 

8. Topping-Off and Nutrient Re-Fills

As the water level goes down, top-off with pH-balanced water without nutrients (topping-off with nutrient water messes up the nutrient levels and can harm the plant).

After 2-3 weeks, your pH will have climbed (to 7.0 or higher), so it’s time to replace your nutrients completely and refresh each plant’s reservoir.

At this time, you will also want to flush your plants in the sink to remove any mineral build-up (white staining on leca).

For a good idea of what this schedule looks like, check out this video.

Optional Step For Plants With Pest Problems

Converting a soil-based plant with a pest problem? Consider giving your plant a bath, first.

This optional step would come just before Step 1, outlined above.

Prepare your sink or an empty tote with a soapy water solution (I’d recommend this vegan/organic/unscented soap).

You won’t need a ton – just a few drops per gallon of water.

Place your plant into the soapy water; container and all. Leave it there to soak for at least 15 minutes (longer is even better). This gives the soap and water enough time to do their job.

When you return, all pests should be killed and bacterias neutralized. Now it is time to remove the plant, slowly, from its container.

You can go about this process in any number of ways. The most straightforward is to lift the container out of the water, let it drain, and then gently pull the plant from its base, up and away from the container.

Process complete – go to Step 1, above.

Potential Issues To Watch For

Despite the general awesomeness of semi hydroponics, there are a few potential issues to watch for when you first get started. 

These problems include:

  • Overwatering
  • Over-fertilizing
  • Not soaking your plants and preparing them for the conversion from soil to an inert growing medium
  • Not giving your plants proper time to adjust to their new environment before setting your new watering schedule

Is Passive Hydroponics the Same as Semi Hydroponics?

There is no difference between semi hydroponics and passive hydroponics. They are simply two different names for the same thing; a simple method for growing plants via an inorganic medium, water, and liquid nutrients rather than in soil.

4 Tips for Success When Growing With Semi Hydroponics 

1. Use Younger Plants for Higher Success Rates

The younger your plants are, the better their chances are at transitioning to semi-hydro with little to no stress. Older plants may lose more leaves or even die.

2. Consider Using a Water Gauge

If possible, insert a water gauge into the reservoir of your semi-ponic setup. That way, there is zero guessings as to the water levels. When they drop, top them off.

3. Gradually Prepare Your Plants

Soaking your plants daily, removing a bit of soil, and replacing it with an inert medium, for a few days at a time, is an alternative way of transitioning them. After four or five days, your plant will be living in a more inert medium than actual soil.

4. Give Your Plants Time to Adjust

After removing your plants from the soil, and placing them into semi-ponic containers, give them time to adjust. If they are losing leaves or looking a little droopy, don’t freak out and throw them back into the dirt (which would likely kill them). 

Final Thoughts About Semi Hydroponics

Semi hydroponics lovingly referred to as LECA, or semi-ponics, by advocates of the growing method, is a great way to convert houseplants from messy soil-based plants to thriving plants that flourish in an inert medium.

Semi hydroponics is also an excellent way to transition yourself from a soil-based gardener to a hydroponic gardener. 

Any way you look at it, semi hydroponics sure does beat the pants off of growing plants in soil!