Let’s go back to plant 101. 

• The less you disturb roots, the faster and healthier a plant will grow. 

• Disturbing small plant’s root system can drastically reduce their vigor and sometimes kill them.

• For you outdoor gardeners, you know some plants transplant badly from container to ground such as cucumbers and beans. Reason being, plants don’t like their roots disturbed. 

This is 100% true in LECA. If you continue to repot frequently, you will send the plant into a state of shock or cause it to stall in growth. So what should you do with overgrown roots in LECA? This needs to be broken down into two sections depending on your pot setup. (I highly recommend reading the pot setup link prior to to the rest of this part.)

In a nutrient stagnant wicking setup (NSW), you are usually working with an inner pot that has drainage, and an outer cache pot that holds your nutrient water. Roots in this setup will eventually grow out of the drainage holes. Leave those roots be. They will grow into the reservoir and it’s perfectly fine for them to be there, they are adapted to the water environment because they grew into it. Over time (6 months+) you may see some of these roots break down depending on the type of plant. For example, my hoya roots that sits in the reservoir over time will decay. Hoyas have larger primary roots and lateral roots, with many root hairs. Over time, I will observe the decay and rotting of root hairs, but not the primary and lateral roots that are more substantial. When these root hairs decay, just use your hands and rip them off or clip them off with clippers. Keep using products like Kelpmax on a monthly basis to continue to stimulate root growth, new roots will replace old roots, and you will rarely have to repot the plant. 

In a submerged setup, it’s harder to get to those roots unless you use a net pot that sits inside a cache pot. If you use the net pot, use the same strategy as above. (I would also highly advise a setup where the bottom of the net pot isn’t sitting right on top of the reservoir so you have some extra room for roots to occupy without getting crushed over time.) If you use a single pot, you can leave the roots in the water reservoir because they grew into the water, and they should be adapted to water. However, there are some plants that cannot have their roots submerged all the time. Hoyas for example, will begin to show signs of root rot if these roots are left in the reservoir constantly. Usually this is around the 6 months - 1 year mark. Your workaround is to maintain a dry/wet cycle, meaning that you should let the plant dry out for a few days before refilling the reservoir. This allows the roots at the bottom of the pot to receive enough oxygen before being submerged again in water. Plants like philodendrons don’t seem to be affected as much. I’m not a huge fan of this setup because over time, your plant will grow bigger, and send out more roots. You will eventually get to a point where you have to water very frequently because the bottom of the reservoir is taken over by roots. Once the plant gets to this point, then you can take it out and reposition it in the pot, maybe do this every 6 months - 1 year.  A better long-term alternative would be to just switch those particular plants to an NSW set up.

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Without going into gory details of how water treatment plants work, I’ll highlight the different stages of treatment for water to keep this brief. 

1. Water treatment plants add aluminium sulphate to water to adjust pH for safety. This compound causes impurities in the water to clump together so it’s easier to remove. Water is agitated so these clumps stick together.

2. Water is allowed to settle for the aggregated impurities to settle, and then removed. 

3. Once large impurities are removed, water is filtered and disinfected. They use fine sand and gravel to further filter the water - much like your Brita filters but on a larger scale. This removes smaller particles and microorganisms. 

4. Finally disinfecting happens using small amounts of chlorine and ammonia to prevent bacterial growth. 

Things in tap water that are bad for semi-hydroponics/hydroponics and how to remove them.

1. Chlorine. As we all know, chlorine is used for disinfecting pools and to prevent the spread of diseases, it’s used in our tap water in small amounts. Many people use tap water for soil-grown plants, and much of the chlorine is removed as it passes through soil. In semi-hydroponics and hydroponics you don’t have the luxury of a natural filter against chlorine. To remove chlorine, simply leave it in sunlight for 12-24 hours. I see many people practice this but a lot of people leave the sunlight part out and leave it on their counter. Remember to leave it out in sunlight. 

2. Chloramine. Similar to Chlorine, Chloramine is used as a disinfectant and depending on where you live, your water may be treated with either or both. To remove Chloramine, you can use tablets (like the ones made for fish tanks) or use sunlight, however it takes longer for it to dissipate. Another way is to use an activated carbon water filter. 

3. Dissolved Minerals. Remember when we talked about water treatment and how water passes through sand and gravel? This process mineralizes the water. Many of you may know the term soft water or hard water. Hard water has high quantities of dissolved minerals, this level can be measured in ppm. My water measures around 150ppm which means it has a moderate amount of dissolved minerals. Anything over 200 is very hard water. Why is this bad for semi-hydroponics? Because out of the minerals, a lot of it is calcium and magnesium (calmag). The presence of large amounts of calmag can lead to nutrient lockout. In addition, this can cause aggregation with other dissolved nutrients and it can affect the pH and nutrient content of the solution. Nutrient lockout means exactly that, your plants can’t access the nutrients in your solution, and can show up as deformed leaves, yellowing leaves, smaller than normal leaves, and new growth dying out. 

In conclusion, your water source matters a lot in semi-hydroponics, especially if you’re going to continue growing your plants this way for the long haul. Tap, well, and rain water often has minerals and dissolved solids that are unknowable unless you get it tested and measured. If you can, invest in an under-the-sink reverse osmosis system, or a portable one. If you’re just starting out, invest in a good carbon-based filtering pitcher. Avoid water softened with salt-based softener, as these will slowly kill some types of plants including orchids and some tropicals. You may be using tap water without any issues for a few months, and it could be that you’re lucky enough to have great water out of the tap, or it could be that it’s too early to tell and you may start seeing issues in 6 months - 1 year depending on how hard your water is. By switching to distilled, filtered, or reverse osmosis water, you can rest assured that your water isn’t providing potentially harmful elements to the long term health of your plants. 

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The difference between organic and synthetic fertilizers is the source of the materials used to provide nutrients. Organic fertilizers like worm castings, egg shells, fish emulsion, blood meal, manure, etc., usually have lower concentrations of macro and/or micronutrients and most are limited in terms of what nutrients any given source material can provide. They are typically more slowly released and work with the biome of soil to break down into a form the plant’s roots can successfully take up. Synthetic or inorganic fertilizers are more concentrated, soluble, and easier to apply in controllable and complete amounts. The nutrients they provide are readily available for uptake by the plant. The downside to synthetic fertilizers is that they need to be replenished or reapplied more often. 

Using organic fertilizers with soil is one thing; using them in a semi-hydro or even hydroponic setup is a completely different one. Soil works in tandem with many organic materials to break them down and make them readily available nutrients for the plant to uptake. While organic hydroponic farming is certainly possible, it does require a recirculating bio-filter system. (source) Since our growing systems are contained and have stagnant reservoirs, this bio-filter system is just not possible. In addition, using things like fish emulsion, banana peel water, etc, are unlikely to provide adequate nutrients in a form readily available for uptake by the roots and they’ll also make your reservoir smell pretty bad.

There is a class of organic fertilizers that contains readily available nutrients as well as slow release organic elements on the market like Foxfarm. I would suggest avoiding these as well for semi-hydroponics if you’re new. The readily available nutrients may be enough to sustain your plant, but the slow release elements makes it harder to control. 

Unless you are a professional and you know how and want to make organic fertilizers work in a closed stagnant hydroponics system, don’t do it, it’s not worth it. Like the link above mentioned, there are documented instances of successful organic hydroponics growing, but these are large controlled flowing systems. If this concept were to transfer to semi-hydroponics for houseplants, you would have to duplicate the effort to balance the system in individual 20, 40, 100 houseplant reservoirs. 

If you’re still not convinced, read the following instagram post series about organic fertilizer vs inorganic fertilizer. Organic doesn’t mean good and inorganic doesn’t mean bad. This series may blow your mind and change your perspective on the entire term “organic”. Part 1, Part 2, and Part 3.

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What is a guaranteed analysis? To simplify for the sake of this article, it’s the numbers you see next to fertilizers. So if a fertilizer has 20-20-20 printed on the bottle representing amounts of macronutrients N (nitrogen), P (phosphorus), and K (potassium), that means it has a guaranteed analysis. You’ll also find a list of percentages of different macro and micronutrients on the label.  If a product claims to provide nutrients for plants, they are required to follow fertilizer regulations. In the U.S. this is regulated on a state-by-state basis; i.e. a fertilizer that wants to sell to residents in every state in the country must register and follow every state’s regulations. The requirement to submit products for laboratory testing and provide a guaranteed analysis on the label, synthetic and organic alike, is consistent across all states.  

Why are nutrients so important?  Feeding your plants in semi-hydro is much more important and consequential than feeding soil plants. Soil holds nutrients and releases them slowly. LECA and other inorganic mediums have zero nutrient content.

The consequences of underfeeding plants include:

• slow growth

• deformed growth

• smaller than normal leaves

• new growth dying off (often associated with calcium deficiency)

• discoloration (i.e., yellowing in established plants can be a sign of calcium/magnesium deficiency)  

The consequences of overfeeding plants include:

• burnt roots

• deformed growth

• sudden decline and death

Many of these consequences typically take several months to a year to show up. Most plants have a healthy reserve of energy, and when it’s used up and it hasn’t been replenishing that energy via proper nutrients, it will exhibit some of the above signs. Similarly when you feed a plant, don’t expect to see results right away, it can also take several months for a new fertilizer routine or a new product to show positive signs. One exception here may be the plant is missing some key micro or macro nutrients, or if it’s exposed to a combination of those and stimulants, then it may exhibit new growth very quickly after a new fertilizing product is introduced. We can all agree that knowing what nutrients go into your plants is really important right? 

I recommend General Hydroponics Trio, Dynagro, really anything with a guaranteed analysis made for hydroponics to let you know what you’re feeding your plants. I cannot state this more, feeding your plants precisely in semi-hydro is much more important and consequential than feeding soil plants. Follow the direction on the packaging and stick to the “mild or general vegetative growth” categories. It’s easy and proven. If you are more experienced you can explore other fertilizer options such as my favorite MSU formulation.

Case Study: An examination and review of Liqui-Dirt / Liquid Dirt

Products like Liqui-Dirt seemingly take all the good aspects of organic fertilizers and combine them into a readily accessible form for plant uptake. Their website lists all these good ingredients with their respective NPKs.  Numbers means it’s really good, right? Nope, this is very deceptive marketing as these numbers correspond to the core ingredients themselves. Without a guaranteed analysis, you don’t know what a fertilizer contains, or how much of each ingredient is present. To give an analogy, I can list all of the nutrition bread, cheese, and meat provides individually, but if I sell you a sandwich and doesn’t say it actually includes bread, cheese, and meat, that nutritional information I gave you is deceptive marketing. Given their product claims to provide “complete” nutrients for plants in any set up, their lack of a guaranteed analysis means they’re not following fertilizer laws as required, and we cannot be sure what their product actually contains.  Astute readers of their website will notice that they state they cannot sell to people living in California. This is precisely because they have failed to follow state fertilizer laws.  

More importantly, private lab analysis of their sister product Noot shows an alarmingly low percentage of macronutrients (or none at all) and demonstrates a complete lack of certain micronutrients it claims to have on the packaging. (source)

In addition, organic products (including fertilizers, since they are used to farm “organic” food stuffs) can voluntarily subject themselves to OMRI review (Organic Materials Review Institute). OMRI analyzes the materials and production processes of products to determine if the product should be “OMRI-listed”. This allows farmers wishing to sell their food products as “organic” to rest assured that the fertilizers they’re using are indeed organically produced and sourced. Additional information about identifying organic fertilizers here. Liqui-Dirt is not OMRI-listed despite strong advertising claims that it’s organic and all natural.

The owner of Liqui-Dirt is now actively pushing this product on the semi-hydroponics community and there is a lot of hype about how wonderful this product is. Try measuring the ppm of this product. It clocks in at a whopping 20ppm for the concentrated dilution, and near 0 for the recommended dilution. When we asked the Liqui-Dirt owner about this, he says “that’s not how organic fertilizers are measured.” There is some truth to this, you can’t measure organic fertilizers accurately this way. But remember our point about not using organic fertilizers in semi-hydroponics / hydroponics? If you can’t measure it, how do you control what your plant eats? Why are you blindly trusting their measurements, a company that’s recommending doubling the dose of the product for semi-hydro when most fertilizers should be reduced by half?

It’s best to use a knowable, controllable fertilizer that provides a guaranteed analysis. Think of it this way, if I’m trying to gain muscles, gain or lose weight, I look towards nutrient labels to keep track of what I eat. I trust that those nutrient labels are accurate and contains the ingredients printed. Putting Liqui-Dirt on your plants is like eating that aforementioned sandwich, but in reality it may be a few strands of cat hair on top of stale potato chips. After a few months of this less-than-ideal diet, I’m going to suffer some serious consequences.

I will gladly change this review once the company provides a guaranteed analysis and updates their packaging in accordance with state and federal regulations.

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First, a primer on plant growth stimulants.

Ray is one of the pioneers of growing orchids in semi-hydroponics. He’s an engineer and a plant nerd, and has done extensive research that has contributed to his grow style. His passion for growing in semi-hydro and orchids led him to create a line of products based on science, and his epiphyte fertilizer MSU K-Lite is one of my favorite products. He describes growth stimulants in three categories. 

Direct Stimulant - These products contain synthetic auxin hormones like naphthalene acetic acid (NAA) and/or indole butyric acid (IBA). Common products in this category are Dyna-Gro’s KLN and Superthrive. When these products are applied to the plant, they accelerate the plant’s natural hormone production and thus, stimulating growth. 

Indirect Stimulant - Ray cites that the only product he’s aware of in this category is Mega Thrive - a urea-based foliar fertilizer that contains molybdenum (Mo) and boron (B). This product also stimulates the plant’s production of hormones.

Shortcut Stimulant - Although some of these products contain some natural plant hormones, Ray categorizes these as a shortcut because the degree of growth stimulation it provides is far greater than would be expected from the auxin content. This is because these products contain minerals, vitamins, proteins, amino acids, alginates, and other polysaccharides and other plant growth regulators, all are produced within the plant - working with natural hormones to magnify the stimulation effect. There are many products on the market claiming to be “plant vitamins”, be careful what you buy! Remember the tip above, demand your products to have a guaranteed analysis because without it, you have no idea what’s in it! Kelpmax is my go-to product in the growth stimulant category. For a full breakdown of KelpMax’s guaranteed analysis, take a look here. 

Now that you understand the different forms of plant stimulants, why should you not use them all the time with every watering? 

Overuse of direct and indirect stimulants can lead to leaf deformation, stunted growth, or even death of the plant. If you’ve heard that Superthrive is a registered pesticide in certain states, that’s 100% true because NAA is a carcinogen, and especially not recommended on edible plants or smokable plants. Excess use of molybdenum can make your plant toxic, so if you have small children or chewing pets, you should stay away from these products altogether to be safe. 

But these shortcut stimulants sound awesome, they have all sorts of vitamins that the plant needs, why don’t we use it all the time? According to Ray -

Plants have a normal physiological cycling of plant hormones – as the root apical meristem (growth front) expands, the cells secrete cytokinins that move upward in the vascular system to stimulate the growth of the plant shoot. As the shoot apical meristem grows, it emits auxins that travel down the vasculum and stimulate root growth. When an outside stimulant is applied, it augments one or the other of those natural hormone supplies, causing a greater growth response with a correspondingly greater secretion of natural hormones that, in turn, accelerates the stimulation of the “opposite” meristem. Think of it like a steadily burning campfire – throw a little gasoline on it and it flares up for a few minutes, then slowly subsides back to its normal level. In stimulated plants, it typically takes between two- and three weeks for the “flare up” to return to normal levels, so we recommend waiting a month, just to be safe. Then there’s the “concentration” factor…

Many orchid growers are used to cutting back on fertilizer concentration while applying it more frequently, but stimulants don’t work that way. With growth stimulants, there is a critical, minimum concentration for them to activate processes in plants; below that, a treatment does nothing. I liken it to operating a light switch. Apply too little pressure and nothing happens. Apply the right pressure, the switch moves and the lights come on. Apply more pressure and again, nothing happens – the light certainly does not get brighter!

I really like his light switch analogy, and his information about the natural cycle. I follow his directions and use kelpmax on a monthly basis. I also use General Hydroponic’s Rapidstart as well, also on a monthly basis. For more information on this topic, please read Ray’s full rundown on Kelpmax. 

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Semi-hydro Facebook groups are filled with members of different experience levels (which is great!) but unfortunately experience level is not upfront and available to us when people comment on a post or provide advice. Know your source. Whenever possible, find out how long people have been growing semi-hydroponically before taking their advice. Find out the particulars of their pot set up, transition approach, success/failure, environmental conditions, etc. Cross-check that advice by using the search group feature. This is useful for browsing how similar questions have been answered in the past but can also be used to gather anecdotal information as to a given approach or plant. In the end, success or failure will vary from one individual to another, even with the exact same plant and (seemingly) the same approach. We all have different environmental conditions and our plants come to us in varying degrees of growth or health. Trial and error is far more useful than crowdsourcing social media for answers.  

Youtube is also a common source of information and mis-information on semi-hydroponic growing. Again, it’s hard to know (impossible in some cases) how long a given individual has been growing plants this way and it’s not uncommon for someone to upload a video tutorial detailing an approach they swear by only to have them turn around and change their approach later (but not update the older video). The prior video is left dangling out there for people to find and attempt to apply without realizing problems arose or adjustments and changes were necessary for long term success.  Obviously, we all like visuals. Be careful what you rely on and take to be absolute fact or truth. 

Finally, I’d encourage you to find your people. Those who will engage in discussions and help you troubleshoot by asking thoughtful questions or challenge your assertions and conclusions. None of these tips were created in my own vacuum, I have found my people and they help me ideate concepts to write about, point out common social media falsehoods, and spend their time helping me create and edit content. Big shoutouts to Alison and Michelle in their contributions to this piece, and especially their diligence to help others in the semi-hydro community with stellar advice.

Do your own research. Experiment in your own environment. Come to your own conclusions. 

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