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.
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