4 Factors affecting Orchid growth

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There are many factors that affect the growth of orchid and flower. You have to know their basic requirement and apply it for your plants.


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Water is the main component in plant cell (about 90%). They use it for photosynthesis, as a solvent , to controlling the temperature and etc.

The requirement quality of water for cutting flower orchids is

pH5.2 – 6.2
Electrical conductivity (EC)< 750 microsiemens/centimeter
Sodium (Na+)< 3.0 milliequivalent/liter
Sulfate (So4 2-)< 10 milliequivalent/liter
Bicarbonate< 1.5 milliequivalent/liter
Soluble Sodium Percent (SSP)< 60%
Sodium adsorption ratio (SAR)< 2
You can use HNO3 or KOH to adjust the acidity

Electrical conductivity value relates to how much mineral salts are in the solution. When the EC value is high, the less water can be absorbed (reduce the fertilizer/pest control). For strap vanda orchids, the total dissolved solids (TDS) should not exceed 250 PPM. For dendrobium, the TDS should not exceed 375 PPM.

Calcium bicarbonate (Ca(HCO3)2 is the mineral salt that you should be aware. They come from ground or mountain water. This salt can coat the orchid’s root. It stops the growth. NaCl and Sodium bicarbonate (Na2CO3) make stem and leaves burn and wither.


Most of Orchids grow well in 60-80% relative humidity. They use water in Co2 fixation period. But don’t make their root too much wet.


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The factors that affect the growth of orchids are light intensity, duration, and wavelength.

For light intensity, this should be measured at noon with clear sky. Some orchids grow well under fully sun light. Some orchids grow well under the shadow. You should consider the light saturation point; it is a point which has the highest oxygen releasing rate. More intensity will not increase the photosynthesis.  The structure of leaf is related to light requirement. The thick and round leaf orchids require fully light. But thin and wide leaf orchids require medium light.

For light duration, the light amount directly affects to the synthesis of carbohydrate. However, the duration of dark period also affects the development of orchids. For example, Rhynchostylis retusa will bloom when night is short. Phalaenopsis pulcherrima will bloom when night is long (16 hours is better than 12 hours night)

For light wavelength, Orchid’s tissue will be damaged when receiving ultraviolet light spectrum. But UV light with 385 nanometer wavelengths can help the antioxidant activity. It will prevent the bacterial damage. Red light at 640-680 nanometer wavelengths is related to the form change of phytochrome. And wavelength at 624-660 nanometer is affected the photosynthesis. It helps generate chlorophyll. Blue light at 430-450 nanometer wavelengths helps about the growth of leaf and stem. The wavelength of 450 nanometer will stop orchid’s elongation. And help to controlling the opening and closing of the stomata, chlorophyll synthesis and photosynthesis. Orchid which is grow under the blue light will have short small and thick leaf and short stem.


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Temperature plays crucial role in respiration system and element synthesis. When temperature decreases the stomata will open for CO2 fixation in CAM orchids. When the environment is hot in noon, the CO2 fixation rate of CAM orchids will depend on the difference of temperature between night and day. The tropical orchids have the best CO2 fixation when daytime temperature is about 25-30 degree Celsius and nighttime temperature is about 15-20 degree Celsius. And warm climate orchids have the best CO2 fixation when daytime temperature is about 15-20 degree Celsius.

The nighttime temperature has more effect on the growth of orchids than daytime temperature. 10 degree Celsius difference between night and day temperature is suitable for growing tropical orchids. But 15 degree Celsius difference can caused plant a chilling injury (yellow leaves and wither).

Plant Nutrition

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Plant nutrition

Carbohydrate from photosynthesis reaction is important to orchid’s growth. However, they require an additional nutrient. When orchids lack of nutrients, it can take about 7 months to show the symptom. Orchids have the ability to move the nutrients from one place to the other place. Especially, The tropical orchids, they can move the food effectively.

The nutrients that affect the orchid’s growth are

Nitrogen (N) is essential for stem and leaves. It is a composition of Amino acid, protein, nucleic acid, enzyme, and chlorophyll. They help carry carbohydrates. And Nitrogen in form of Urea helps to increase an absorption to leaf’s cell wall in low light environment. Orchids which have high contents of Nitrogen can have these following symptoms; dark green leaves, easy to crack, hard to bloom, weak to disease, and bad root system. Orchids which Lack of Nitrogen can have these following symptoms; slow growth rate, pale leaves, and stunted size.

Phosphorus (P) is essential for orchid’s inflorescence. It is a composition of sugar phosphate, nucleotides, nucleic acid, phospholipids, and many types of coenzymes including adenosine triphosphate (ATP). So, Phosphorus is relevant to the respiration system. It will be stored in young leaves and inflorescence. Too much Phosphorus content can cause a lacking of Nitrogen, Zinc, Iron, and Cobalt. When plants are lacking of Phosphorus, They will have a slower growth, weak, thin stem, stunted size, few roots, dark green to purple leaves, and weak seed. For cattleya orchids, Phosphorus fertilizer can cause a lower content of phosphorus and calcium in leaves.

Potassium (K) is a coenzyme that can activate many types of enzymes. It helps in synthesis of ATP, controlling stomata, absorption of Nitrogen, and moving the nutrients to where the plant needs. The content of Potassium should be similar to the Nitrogen content excepts for the plants that receives much of light, they will require Nitrogen more than Potassium. When the Potassium contents is high, the plants will have a lacking of Nitrogen, tip of young leaves will wither, tip of old leaves will burn and it will affect the absorption of plus ion mineral. When the Potassium contents is low, they will have a slower growth, short stem segment, the tip of leaves will die, and leaf edge will turn to brown, and black spot incur.

Magnesium (Mg) is a composition of chlorophyll and cofactor enzyme of phosphorylation process. When the Magnesium content is high, they will lack of Calcium, when the Magnesium content is low, the leaf will turn to green yellow color. The tip will be bent and burn. Some orchids will have a shorter leaf and slow growth rate. The higher content of Mg can cause a lower content of Nitrogen, Phosphorus, Potassium, Iron, and zinc in root.

Calcium (Ca) is an essential composition of middle lamella and alpha amylase enzyme. They work with Boron in pollination process. Too much Calcium can cause lacking of Mg. The shortage of Ca can stop an orchid from growing and the tip of root will wilt. The symptom is similar to lacking of Potassium.

Sulphur (S) is an essential composition in protein such as coenzyme A (respiratory process), Vitamin B1 (Thiamine) and Biotin. They are important in creating of chloroplast. Too much S can be caused from the pollution in air. The plants will stop grow, new leaf will be small, and mature leaf will be wither.

Iron (Fe) helps in chlorophyll synthesis. We add it to make flower has a darker color. When Iron is shortage, the young leaf will turn to yellow and the color of flower will become pale.

Boron (B) works together with Calcium in pollination process. Too much Boron can cause young leaf has a brown line. But lacking of Boron can cause an undeveloped seed.

Zinc (Zn), when orchids receive too much Zinc, they will have a symptom of lacking Fe and Mg. And when they receive it not enough, the leaf will become yellow, small and wrinkle.

Copper (Cu), when Cu content is too much, they will cause a lacking of Fe. When content is low, The new stem will be small and distorted.

Manganese (Mn) helps in photosynthesis reaction. When Mn is too much, they will stop grow and has a brown spot and lack of Fe. When Mn is not adequate, The leaf turns to yellow and also has a brown spot.

Molybdenum (Mo), when orchids lack of it, the mature leaf will become yellow (begin from the petiole) and twist.

Chlorine (Cl), too much Chlorine cause leaf burn. And too low Chlorine cause leaf wither, color change and dry.  

REF: ว่าด้วย กล้วยไม้: ศาสตร์และศิลป์ เพื่อการพัฒนา

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