I have experimented with lots of different ways to water orchids. Learning how to properly water orchids took a lot of experimentation and fine-tuning. Don’t be surprised if it takes a while to get it right, but don’t give up.
To master watering orchids, it is essential to water from above with fresh, pure water. For orchids with water storage, pseudobulbs, water when the potting mix is approaching dry. Otherwise, for orchids without water storage, and without pseudobulbs, keep the potting mix barely damp.
Knowing when and how to water orchids is an important factor in becoming a successful orchid grower. This article unlocks effective watering techniques.
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When it comes to watering and fertilizing orchids, pH is an important factor to consider. Orchids need the right balance of acidity or alkalinity in their potting mix and water to take up nutrients effectively. But are orchids uniformly “acid loving” plants? What is the ideal pH range for different orchid types?
The Short Answer – It Depends
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 25,000+ orchid species.
That said a pH between 5.5-6.5 tends to suit most common epiphytic orchids well. But specialized orchids may deviate from this norm. Understanding what conditions your particular orchids require allows you to tailor care accordingly.
Examining pH in an Orchid’s Native Habitat
To determine whether an orchid naturally grows in acidic or alkaline environments, consider:
- Where it grows – on trees, limestone, or terrestrial?
- The geology of its native region – abundant in limestone and basalt or sandstone?
- 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 and are adapted to mildly acidic conditions. Their native pH is influenced by:
- Rainwater: Naturally pH 5.5-6 due to carbonic acid.
- Decaying vegetation: Releases organic acids as it decomposes.
They are well suited to 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: Buffers rainwater pH upward through calcium carbonate.
- Hard water runoff: Leaches minerals into the environment.
Terrestrial Orchids
Terrestrials like cymbidium and calanthe grow in soil. Their ideal pH depends on the native 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 Your Orchid’s pH is Too High or Low
Orchids will show signs of distress if their pH requirements aren’t met:
Symptoms of High pH
- Reduced flowering
- Smaller leaves
- Leaf tip burn
- Nutrient deficiencies
Symptoms of Low pH
- Slow growth
- Yellow lower leaves
- Root loss
- Iron toxicity
Monitor plants carefully and adjust pH accordingly if issues arise.
Best Practices for Watering Orchids Based on pH Needs
Tailor your watering practices to match your orchid’s preferences:
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For orchids preferring low pH, use rainwater, reverse osmosis water, or acidify tap water.
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For orchids wanting neutral to alkaline conditions, use hard tap water or add limestone to irrigation.
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Flush pots regularly to prevent mineral buildup and pH jumps.
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Include drainage holes to leach excess salts after watering.
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Test pH periodically with a soil probe or meter to ensure it’s in the ideal range.
Using Acidifiers to Lower pH
If your water or media pH is too high for your orchid, you can lower it by adding acidifiers like:
- Citric acid (mild)
- Phosphoric acid
- Sulfuric acid
- Vinegar or acetic acid
Use pH test strips or a meter to monitor the pH as you titrate these in. Go slowly and re-check to prevent overshoot.
Raising pH Naturally for Alkaline-Loving Orchids
To increase pH for lithophytes and some terrestrials, add limestone-based components:
- Crushed oyster shell
- Dolomite lime
- Calcium carbonate
- Eggshell fragments
Over time these will buffer potting mix pH upward if needed. Monitor pH to ensure it stays in the ideal range.
The Takeaway – Know Your Orchid!
Rather than assuming all orchids want highly acidic conditions, consider their natural habitat. This provides clues to their optimal pH for healthy growth and blooming. Never be afraid to tinker with pH to find an orchid’s “sweet spot.” Paying attention to their preferences allows you to mimic nature and unlock their full potential.
Mix Distilled Water with Tap Water
If you are growing only a few orchids, here is an easy way to improve your water quality. Mix distilled water with tap water. Test a 1:1 blend and see what your TDS and pH levels are. Though a few adjustments may need to be made, 50/50 is a good starting point. If you are growing lots of orchids, you may need to use another method.
When water is forced through filters, the dissolved solids are left behind, and the pure water flows into a collection tank. This is all that reverse osmosis is. The dissolved solids go on to the sewer, septic, or groundwater – however, you dispose of water. This means that inevitably, there is some water waste.
Because RO water is so pure, minerals and fertilizer, needs to be added back into the water. Check the RO water to make sure it has enough dissolved solids to be safe for your orchids before you use it.
To get a pH reading, measure out a large amount of water, like a 10-gallon barrel, and add the right amount of fertilizer for the volume of water. Then, take the pH reading.
To adjust acidity, use a few drops of citric acid or pH Down. To make the water more basic, use potassium hydroxide or pH Booster.
If you want to balance the pH, use only a few drops. Wait a few hours and then take another reading.
The easiest way to test pH is to buy litmus strips or water quality meters.
Let’s Talk About pH
When you measure acids and bases with pH, you use a scale that goes from 14 (most basic) to 0 (most acidic), with 7 being neutral. Orchids prefer a reading between 5. 5 and 6. 5. Each number is 10 times more acidic, or basic, than the next.
The amount of free hydrogen and hydroxyl ions in the water is what makes bases and acids different. The more free hydrogen ions the more acidic the water. The more free hydroxyl ions are in the water, the more basic the water.
NOTE: As an example, rainwater pH varies across the US between 4.3 and 5.3, much lower than many cities with tap water with pH readings as high as 8 (See usgs.gov).
For most of us, the water that comes out of our faucets is not good enough to water orchids. This is because tap water, even spring water, has a lot of minerals and salts in it. If you’re on city water, chlorine is also in it.