In nature, orchids grow on rocks and in trees. They get by on a slim diet of organic matter that collects at their roots from the wind and rain. This can be anything from decaying tree bark to bird droppings.
Complex interactions involving live bacteria, enzymes, and microbes break down this organic matter so the plant can absorb it.
This process is almost impossible growing at home with potted plants. Potting mixes are sterilized, killing the bacteria, enzymes, and microbes needed to transform organic matter into a form your plants can use. So, potted plants rely on you, the grower, to provide the nutritional elements - in a form the plant can use.
Don't confuse "plant food" with "plant fertilizer or plant nutrients". Plants manufacture their own "plant food". Using the power of the sun, they combine air, light, and water to make carbohydrates, which they use for growth. This process is called "photosynthesis". Photosynthesis makes the "real food" that plants use to stimulate new growth.
"Plant nutrients", on the other hand, are the mineral elements collected by the roots to enhance photosynthesis. Plant nutrients (or fertilizer) cannot compensate for the lack of real food plants need for growth (air, light, and water).
So, before you give your plants that extra dose of nutrients (fertilizer), make sure they're getting the "real food" they need for growth - air, light, and water.
Without them your choice of nutrients (fertilizer) won't matter.
Urea is an inexpensive form of nitrogen, the primary ingredient in all fertilizers. Orchids can't use urea until it is broken down by enzymes or bacteria. That's great for outside plants, but sterilized potting mixes don't contain the enzymes needed to convert urea into something the plant can use.
Unused urea turns to salt and actually harms the plant's roots because orchid roots can't tolerate salt. If you're using a plant food that has urea on the label you might actually be harming your plants! Look for nitrate nitrogen or ammoniacal nitrogen on the label, not urea.
Correct nitrogen source
Never use urea!
All plants need 16 essential elements for optimum growth. Look on the back panel of the package - are there 16 elements in your fertilizer?
To lower costs, most fertilizers skip elements - leaving your plants to rely on the potting material to provide what's missing. How do you know what your plants are really getting with this hit-or-miss approach?
Hydroponics doesn't rely on the potting mix for any nutritional value. That means hydroponic fertilizers always have all 16 nutritional elements plants need, in a form they can absorb immediately.
In nature, houseplants live on the forest floor where their roots grow in a combination of soil, decaying leaves, and animal droppings. They choose their nutrients from an "all you can eat" smorgasboard of mineral elements.
Orchids, on the other hand absorb their nutrients high up in the trees. The water and nutrients they get can be sparse but they're cleaner and more pure than the water and nutrients houseplants find on the forest floor.
Orchids are naturally more finicky than houseplants about what fertilizer ( or nutrients) they get.
A good nutrition program for orchids requires a quality fertilizer that has all the elements plants need for growth - in a form the plant can use immediately. No complex biology necessary.
Don't think there's a difference in fertilizers? Ask your plants! They feel the difference immediately.
More on plant nutrition -
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