Orchids are among the most popular and beautiful flowering plants in the world With over 25,000 species, orchids come in a stunning array of colors, shapes, and sizes But when it comes to caring for these exotic beauties, many gardeners have questions. One of the most common is are orchids acid loving plants?
The short answer is – it depends. While many orchids do prefer mildly acidic conditions others originate from naturally alkaline habitats. There is no single optimal pH for all orchid species.
By examining an orchid’s native habitat and growth habits, we can tailor care to match its preferences. This allows us to unlock an orchid’s full potential for healthy growth and maximum flowers.
Examining pH in an Orchid’s Native Habitat
To determine whether an orchid naturally grows in acidic or alkaline environments we should consider
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Where it grows – epiphytic on trees, lithophytic on rocks, or terrestrial in soil?
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The geology of its native region – abundant in limestone and basalt or sandstone?
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Water sources it’s exposed to – soft rainwater or mineral-rich runoff?
The habitat provides clues about ideal pH. Mimicking those natural conditions often benefits orchids.
Major Orchid Types and Their Preferred pH Levels
Epiphytic Orchids
Epiphytes like phalaenopsis, cattleya, and oncidium grow on trees. They are adapted to mildly acidic conditions influenced by:
- Rainwater (pH 5.5-6)
- Decaying vegetation releasing organic acids
They thrive in a pH of 5.5-6.5.
Lithophytic Orchids
Lithophytes including phragmipedium, paphiopedilum, and vanda grow on limestone outcroppings. Here, the pH is naturally neutral to alkaline (pH 7-8) due to:
- Limestone geology buffering rainwater pH upward
- Hard water runoff leaching minerals
Terrestrial Orchids
Terrestrials like cymbidium and calanthe grow in soil. Their ideal pH depends on the location:
- Sandy or acidic soils – low pH below 5.5
- Limestone or basalt terrain – alkaline pH around 7-8
- Tropical forests – acidic humus pH around 5.5-6.5
Signs of Improper pH
Orchids will show signs of distress if their pH requirements aren’t met:
High pH Symptoms
- Reduced flowering
- Smaller leaves
- Leaf tip burn
- Nutrient deficiencies
Low pH Symptoms
- Slow growth
- Yellow lower leaves
- Root loss
- Iron toxicity
Monitor carefully and adjust pH accordingly if issues arise.
Best Practices for Watering Based on pH
Tailor watering practices to match orchid preferences:
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Acid lovers – use rainwater, reverse osmosis water, or acidify tap water
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Alkaline lovers – use hard tap water or add limestone
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Flush pots regularly to prevent mineral buildup
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Include drainage holes to leach excess salts
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Test pH periodically to ensure ideal range
Adjusting pH
To lower high pH, use mild acidifiers like citric acid or sulfuric acid. Go slowly and recheck to prevent overshooting.
To raise low pH for alkaline orchids, add limestone-based components like oyster shell or dolomite lime.
The Takeaway
Rather than assuming all orchids want acidic conditions, consider their natural habitat. This provides clues to their optimal pH for thriving. Paying attention to their preferences allows us to mimic nature and unlock their full potential.
Reverse Osmosis (RO) Water
Reverse Osmosis is a form of water purification which removes dissolved solids from water. Because it has no dissolved solids, it doesnt have anything to “buffer” the effect of fertilizer added to it. Our FEED ME! MSU Orchid Fertilizer is the original fertilizer that was used by Michigan State University in the study of orchid fertilizers. RO water is a form of pure water just like rain water. Fertilizers that contain Urea as a nitrogen source when used with pure water will become too acidic and will tend to drive the orchid mix down.
Tap water varies greatly across the United States and the world. In some states the tap water is pretty good, low in dissolved solids and quite suitable for use with orchids. In many states, however, tap water has too many dissolved solids. One advantage with municipal water is that many water companies must publish their water quality reports online. Ours is online, our water comes from the Potomac river. In looking at this report we can see that our tap water tends to be hard, it has 120-130 PPM of solids, while our neighbors to the east get the less hard Patuxent water that is softer, around 60-65 PPM. When we measure our tap water it varies from day to day and goes as low as 100 PPM and as high as 200 PPM. As a general rule of thumb water that has less than 100 ppm of solids is good. If water is too hard, one way to reduce the effective hardness of the water is to add Citric Acid. Tap water also may contain high levels of fluoride and chlorine. Levels above 1 PPM are too much and in the case of chlorine, levels above 1 PPM are commonplace. From our water report we can see that our water contains acceptable levels of fluoride but not of chlorine. Luckily Chlorine will evaporate over time or can be removed with a filter. This is why many folks choose to fill their watering containers and then let them sit for a day before using the water on the orchids. The accomplishes two goals, the chlorine evaporates and the water reaches room temperature.
The chemical composition of well water is unique to the well it is drawn from. In order to determine what is in well water, it should be tested before being used on orchids. Once the makeup of the water is understood, the same rules as tap water apply.
How To Feed Your Acid Loving Plants
FAQ
What is the best fertilizer for orchids?
Growers suggest using a “balanced” fertilizer such as 20-20-20 that includes all “necessary trace elements.”
Are orchids acid loving?
For most orchids we recommend a pH between 5.5 and 6.0. To lower pH, use Citric Acid. To raise pH use Lime or Oyster Shell.
What do coffee grounds do for orchids?
What does Epsom salt do for orchids?
Not only does it help with the production of chlorophyll, it aids in cell construction, proper hydration, and flushes out the orchid from salt residue.Oct 16, 2021
Do orchids like acidic soil?
Yes, orchids typically prefer acidic soil with a pH of 5.0 to 6.5. In general, they grow best in soils that are slightly acidic or neutral. To maintain the ideal soil pH for orchids, you can add peat moss or bark to your potting mix.
Do orchids have a different pH?
Depending on the species of orchid you’re growing, it will have adaptations to habitats that may have different pH. However, the majority of orchids we keep are epiphytes and have adapted to rain water which has an acidic pH of 5.5 due to carbonic acid (from CO2), and those orchids will fall into the range noted in the graphic.
Do Orchids need acidic or alkaline conditions?
Also, like the greater world of non-orchids, there are many species that specifically require acidic or alkaline conditions. We should be pragmatic and recognize orchids have adapted to survive where other “fast-growing plants” will not. Orchids have adapted to grow slower and steadily in volatile areas where non-orchids simply cannot survive.
What pH do Orchids need?
This is a hotly-debated topic online with hobby orchid growers assuming, 5.8 pH is the magic pH, where you get optimum nutrient availability and uptake in orchids; however, I call bluff on the necessity of that exact pH for all orchids.
Why does adjusting the pH matter for orchids?
There are two primary components of water that you need to understand (pH and water hardness), and those two concepts cascade into the how and why adjusting the pH matters for orchids. The acidity or basicity of your water is determined by the pH. Acidic water is under a pH of 6.5, basic water is over a pH of 7.5.
What soil do Orchids need?
When it comes to orchids, there is a wide variety of plants and their soil requirements can vary greatly. Generally, orchids prefer to be planted in soil that is slightly acidic, with a pH of 5.5 to 6.5. However, some varieties of orchids, such as Phalaenopsis, prefer a more acidic soil, with a pH of 4.5 to 5.5.