By: Amy Grant
Do you love orchids but find them difficult to care for? You aren’t alone and the solution might just be semi-hydroponics for houseplants. What is semi-hydroponics? Read on for semi-hydroponics information.
Semi semi-hydroponics, ‘semi-hydro’ or hydroculture, is a method for growing plants using an inorganic medium instead of bark, peat moss, or soil. Instead, the medium, usually LECA or clay aggregate, is strong, light, very absorbent, and porous.
The purpose of using semi-hydroponics for houseplants is to make their care easier, especially when it comes to under or overwatering. The difference between hydroponics and semi-hydroponics is that semi-hydro uses capillary or wicking action to uptake nutrients and water held in a reservoir.
LECA stands for Lightweight Expanded Clay Aggregate and is also referred to as clay pebbles or expanded clay. It is formed by heating clay to extremely high temperatures. As the clay heats, it forms thousands of air pockets, resulting in a material that is lightweight, porous, and highly absorbent. So absorbent that plants often do not need additional water for two to three weeks.
There are special containers with an inner and outer container available for semi-hydroponic houseplants. However, in the case of orchids, you really only need a saucer, or you can create a DIY semi-hydroponics container.
To create your own double container, use a plastic bowl and poke a couple holes in the sides. This is the interior container and should fit inside the second, outer container. The idea is that water fills the bottom space as a reservoir and then drains off near the roots. The plant’s roots will wick the water (and fertilizer) up as needed.
As mentioned, orchids benefit from the use of semi-hydroponics, but nearly any houseplant can be grown this way. Some may be more suitable than others, of course, but here is a short list of good candidates.
It takes time for plants to get used to semi-hydroponics, so if you are just starting, use your least expensive plant or take cuttings from them instead to start new houseplants.
Use a hydro formulated fertilizer and allow water to run through the pot to flush any accumulated salt away before feeding the plant.
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I am often asked if a particular plant will do well in Semi-Hydroponics™, and my response is usually “probably, but it depends…”
In reality, almost any plant can be grown in S/H Culture, but it really depends less on the plant, and more upon how Semi-Hydro™ and the rest of your cultural conditions combine to meet the needs of the plant. This article, therefore, is more about how readily the plant will take to the culture, rather than if it will or won’t.
In general, I’d say the single, most important thing to consider is the relationship between temperature and humidity. Because of the open, airy nature of a moist semi-hydroponic pot, if your conditions favor rapid evaporation, you should anticipate the root zone being a few degrees cooler than the air surrounding it. That becomes important if your temperature is marginal for the plant you want to grow, as the cooling of the root system may be a problem. I have most often seen this with phalaenopsis.
Phalaenopsis are really “hot growing” plants that rarely see temperatures below 70°F in nature and thrive in triple digits. Fortunately, they are tolerant of our preferred temperature range, so are great houseplants. If your air is very dry however, and you keep the room air-conditioned or push the thermostat down in winter to save energy, the evaporative cooling from the pot might make the root zone too cold, and “cold and wet” is a terrible combination for the roots.
Moving on, when deciding about a specific plant, I look at the plant structure, growth and flowering habit, and it’s natural habitat.
Plants with pseudobulbs have a built-in water storage vessel, so may not need the constant moisture supply, but most do just fine. Bulbophyllums, which like to stay well watered, do great in S/H culture, pseudobulbs notwithstanding. Plants with no pseudobulbs seem likely to be more of an “automatic” for S/H, but there are exceptions to that, as well. Be wary of vandaceous plants, for example, unless you grow them in warm, dry, in-home conditions (I recommend against it, but there are too many folks out there successfully growing them that way for me to argue with!).
As far as growth habit goes, even if the plants would ordinarily like the culture, if they are climbers or rangers – like the bulbo’s – I tend to mount them instead. Likewise with plants with pendant growth, such as paraphalaenopsis.
As far as flowering habit is concerned, if the inflorescence grows down, like stanhopeas, forget S/H!
Natural habitat plays a big role – obviously a plant coming from a rain- or cloud forest can appreciate the moisture, while one that gets parched by trade winds whistling through upper tree branches is less likely a good candidate.
All of those factors are evaluated together and as a matter of degree, rather than a simple “yes/no,” and when it comes to hybrids (where the “natural” habitat is likely a greenhouse), I look back to the genera and species in their backgrounds.
Semi-Hydroponic™ culture can actually be a great help if you’re “pushing the limits” of your temperatures with the plants you grow: the evaporative cooling from the constantly-moist medium can allow cooler-growing plants to thrive under warmer conditions than they might normally prefer.
Hydroponics is a form of gardening that uses no soil, but instead grows plants in a solution of water and nutrients. A hydroponic system can grow plants and vegetables faster than growing outdoors in soil, and hydroponic systems can be used year-round. Plants grown hydroponically often yield more, require less space, and use less water than with conventional gardening. A hydroponic system also can be an ideal solution for apartment dwellers and urbanites who do not have an outdoor gardening plot.
Four systems are suitable for beginners getting started with hydroponic growing: wick, water culture, and ebb and flow. More advanced systems include the nutrient film technique and the aeroponic system. The easiest plants to start with are greens like lettuce, spinach, Swiss chard, and kale herbs like basil, parsley, oregano, cilantro, and mint and fruiting plants like tomatoes, strawberries, and hot peppers.
Just when you thought you got the hang of growing houseplants in potting soil (or if you’re a doting plant parent, a special homemade mix someone on the internet told you to use) comes a new trend – hydroponic houseplants! Or, “semi-hydroponic” to use the more technical term that is used when describing the trend. How do you grow houseplants semi-hydroponically? Do they grow this way? But first, maybe we should ask the question – why?
Why grow semi-hydroponically?
I think for most casual houseplant growers, this method is attractive because it is a challenge. Something new to try after you’ve mastered growing houseplants the old-fashioned way. And quite possibly a pandemic project to provide a distraction after being cooped up in the house for months on end. But are there benefits to growing houseplants this way? Turns out, there are some.
Many articles you find on the subject state that semi-hydroponic houseplant growth can be beneficial for those who struggle with chronic over- or under- watering. The media used for semi-hydroponics is a big, porous puffed clay stone called hydroton or LECA (Lightweight Expanded Clay Aggregate, of course we have to have an acronym!). It is used in some hydroponic vegetable (and other plant) production systems. The large pore spaces it creates and the wicking action it does in the container helps keep a balance of air and water for the roots. The #1 leading cause of death among houseplants is overwatering – it creates a lack of air in the potting media, the roots lack oxygen (called hypoxia), and are either damaged or die. This can also make it easier for fungal infections to cause root rots. But how can you stop from overwatering plants if you’re growing them in water? We’ll talk about that in a bit when we talk about the “how to”.
There are some houseplants, like epiphytes, that might also benefit from having a media that isn’t like soil. Plants that are used to growing on tree bark, or in rocky environments in their native habitat that might actually perform better in a media that is a large, rough pebble that does kind of resemble the texture or tree bark or stones. There are lots of tropical houseplants that also grow in areas with high levels of large particulate organic matter like chunks of wood and bark. Plants from boggy environments that have high water requirements or grow in a more “mossy” type soil might also benefit.
One other application of this method is for propagation of cuttings. Many houseplant growers like to propagate cuttings in water, but this often isn’t the best practice because the water can be depleted of oxygen (causing hypoxia and rot) or become spoiled or soured (and cause infections). Most horticulturalists will recommend propagation in a light media like seed starting mix, perlite, or sand. But keeping water consistent without overwatering is difficult in this situation, and media can also be a vector for disease. The air space and wicking action of the LECA media used for semi-hydroponics can help keep cuttings hydrated without the issues of water propagation. This method is commonly done in clear class containers, so there’s the added benefit of being able to see root growth to monitor progress.
How do you grow semi-hydroponically?
Of course, in this short article we won’t be able to cover every detail, so if this is something you’re interested in trying, I’d suggest some self-study. I’ll be covering some of the basics, but there’s a lot more to learn.
Kratky hydroponic method Photo: UpstartFarmers
First, this method somewhat resembles one of the simplest forms of hydroponic production that lots of home hydroponic gardeners use, called the Kratky method. In this passive hydroponic method, a plant is suspended above a water-based nutrient solution. At first planting, the nutrient solution is right below the plant, close enough for a few inches of the roots to touch the solution. As the plant grows, the roots elongate and the nutrient solution level is reduced to keep just a few inches of the roots submerged. This allows the roots to take up solution, but the space between the plant and the solution allows a majority of the roots to be surrounded by air to avoid the issues of hypoxia.
In semi-hydroponic houseplant growing, a container (usually clear glass, at least for beginners) is filled with the LECA media and the plant’s roots are distributed through the media. (The media should be washed and soaked in water first, to remove dust and allow it to hydrate.) It is easier if it is a young plant or recent propagation so you don’t have too many roots to deal with (you may need to root prune larger plants). Smaller plants will also withstand the shock of going to this system, especially if they’re moving from a potting soil media. (Note: Clear glass container + nutrient solution + light = algae. Be prepared to clean up the algae from time to time.)
A (dilute) nutrient solution is added to the container. The roots should not be submerged in the solution, but rather it should be added to a level where it will wick up through the media to surround the roots. The basic rule of thumb is to fill the container about 1/3 of solution, but if the container is exceptionally large or the roots are very small, you may need to fill it higher to make sure the media around the roots stays hydrated.
This nutrient solution is one of the trickier parts. You can use a general all-purpose hydroponic nutrient mix, available in lots of garden centers now or online. You can also try some of the general houseplant fertilizers or ones specific to whatever houseplant you’re trying to grow. You’ll want one with micronutrients as well as the macronutrients like N-P-K – since we’re growing without soil or an organic matter based media you’re going to have to supply all of the plant’s nutritional needs. You’ll want to mix the solution between ¼ – ½ the recommended strength – you’ll need to see what works for you and your plant. And then you’ll want to pH balance the water to create the right environment for the plant and make sure that nutrients are available for uptake. The pH range for most plants is between 6.0 and 7.0 (aim for 6.5), unless you have one with specific needs. For this you’ll either need pH test strips or a meter (which you can now get for less than $20 online) and some acidic and basic solutions to adjust pH (you can use some household items like vinegar to do this, but your best bet would be solutions specifically prepared for adjusting hydroponic or aquarium pH levels commonly referred to as “pH up” and “pH down”). This pH adjustment is a lot easier (and maybe unnecessary) if you start with distilled or reverse osmosis water (or if you have a really good water filter that removes dissolved solids). The pH levels and dissolved solids in some tap water makes it hard to adjust (my water here in Nebraska is very basic because it is very heavy due to high calcium levels, which also throws off the nutrient balance). Rainwater or melted snow can also work (though may not be pH balanced).
You want to keep the solution topped off so that the media stays sufficiently moist. As with hydroponic production, plants pull nutrients out of the solution at different rates, so you can get build-up of some nutrient salts over time that could result in poor growth and even toxicity. To avoid this, every few weeks (or more often if your plant is a heavy drinker) you might need to perform a flush, where you drain off the nutrient solution, give a quick rinse with tap water, and start over with fresh nutrient solution.
More experienced growers might graduate to using this method in containers other than clear glass. This adds a level of challenge, since you can’t automatically assess the level of nutrient solution by visual inspection. The use of self-watering pots that have net pot or hole-y insert pots are commonly used for this. Or you can buy net pot or orchid pot plastic inserts to use in any non-porous container you desire. Growing in net pots can make the flushing process easier, since you can just pop it out of the container and run tap water through it. Otherwise, you’ll have to find a way to pour the tap water out of the container or
completely remove the plant and wash the media.
What can I grow semi-hydroponically?
Well, you can try with a lot of different plants. I don’t know that there’s a list of plants out there for do’s and don’ts, but there are a few good candidates to try. Most tropical houseplants are good candidates. I’ve seen lots of articles on orchids, and I just recently put a rescue phalaenopsis in semi-hydroponics. Other epiphytes like holiday cacti and bromeliads are also good candidates – think of things that like to grow on trees/treebark. Hoya, which are all the rage in houseplant circles, are also candidates due to their mostly epiphytic habits. Lots of tropicals like Monstera, Philodendron, and Pothos also do well in this system.
Things that probably won’t do the best in this system are ones that don’t like to have “wet feet” – I’m thinking mostly desert cacti and succulents. But some of the LECA lovers that I talked to said that some succulents, like “string of pearls” and other strings of things (hearts, dolphins, turtles, etc) do grow well. But if we take a look at their natural habitat, where they grow over rocky outcroppings, it makes sense.
There isn’t really an exhaustive list, so you might want to experiment if you’re wanting to try it out. As long as it isn’t an expensive plant (and there are lots of expensive houseplants out there), a little experimentation can help you find the plants that would work best for you and your situation.
Growing houseplants semi-hydroponically isn’t for everyone. Getting everything just right can have a learning curve, especially if you weren’t great in chemistry class. But, it can be a fun way to challenge yourself and may also benefit your plants in the right situations. It is becoming so common that the materials are getting easier to find – many garden centers now carry the LECA and hydroponic supplies, you can always order them online, and you can even find small bags of the LECA/hydroton in the ever expanding houseplant section at IKEA (of all places, if you’re lucky to have one). So if you’re up for a challenge, give it a try! You might find a fun new way to grow houseplants….or a new way to kill houseplants! But the fun will be in the trying.
ในการสร้างภาชนะคู่ของคุณเองให้ใช้ชามพลาสติกแล้วเจาะรูสองรูที่ด้านข้าง นี่คือภาชนะภายในและควรพอดีกับภายในภาชนะที่สองด้านนอก แนวคิดก็คือน้ำจะเติมพื้นที่ด้านล่างเป็นอ่างเก็บน้ำแล้วระบายออกใกล้ราก รากของพืชจะดูดน้ำ (และปุ๋ย) ขึ้นมาตามต้องการ
ตามที่กล่าวไว้กล้วยไม้ได้รับประโยชน์จากการใช้สารกึ่งไฮโดรโปนิกส์ แต่เกือบทุกชนิดสามารถปลูกด้วยวิธีนี้ได้ แน่นอนว่าบางคนอาจเหมาะสมกว่าคนอื่น ๆ แต่นี่คือรายชื่อผู้สมัครที่ดีสั้น ๆ
พืชต้องใช้เวลาในการกึ่ง ๆ – ไฮโดรโปนิกส์ดังนั้นหากคุณเพิ่งเริ่มต้นให้ใช้พืชที่มีราคาแพงที่สุดของคุณหรือใช้กิ่งไม้จากพวกมันแทนเพื่อเริ่มปลูกต้นไม้ในบ้านใหม่
The most time consuming part of this whole process is removing the plant from organic medium such as soil or bark, and ensuring the roots are clean of organic matter. Some plants such as Aglaonemas (Chinese Evergreen) have very thick roots which makes the process very easy, and some other plants such as Hoyas that have very fine and thin root systems that cleaning them becomes extremely tedious. Thin roots plants are also harder to transition because it’s hard to remove all the organic matter. Check out the Plants in LECA section for more information on a specific plant.
Alocasia is cleaned and ready to be potted in LECA.
When soil is left on roots and placed in LECA, it will be in a continuously wet environment. When soil is left on healthy roots and in contact with LECA, the soil will continue to wick moisture from the LECA so that the roots will be continuously wet. Some plants will be ok with this and adapt to the added moisture but most plants do not thrive in these environments. Prolonged exposure to a wet environment will cause root rot, which causes the plant to decline in health.
When prepping a plant to be moved into LECA, its best to clean off the organic materials as best as you can. This will allow the plant roots to make direct contact with LECA. Once the root adapts to the environment, it will adhere to the LECA to draw moisture when it’s needed. If you can’t clean the root without destroying it, my advice is to destroy it by trimming it off. Any soil left on the roots (especially thin roots) will eventually lead it to rot off anyway, and even worse, affect the roots around it with rot.
If you can’t clean off all the soil, set the plant in some water for the soil to come off naturally. This will likely cause some of those roots to rot off but at least you can keep an eye on it and wait for water roots to come in.
Last resort, just can’t get the soil off - you have three options. One is to remove all of the roots entirely and treat it like a cutting, the other is to plant it anyway but flush frequently, applying products such as Physan 20, and unpotting / repotting to trim away the roots. Lastly put it back in soil and abort. :D