Skip to main content

Fanless orchid culture part 1: the air requirements of orchids

Almost any website and book where cultural information of orchids can be found, mentions that air movement is essential for the survival and growth of these magnificent plants. Some of the most important effects are cooling, temperature distribution and preventing disease from bacteria and fungi. All these factors are essential when the natural habitats of orchids are considered. There are a variety of ways to supplement air movement, the most popular being fans. Fans are not ideal; they may create areas with excessive air movement which can dry fresh buds (as I have learned) while leaving the other edge of the grow space with limited air to prevent algae and fungal growth. Fans can also occupy a significant portion of space. In the orchidarium for miniature orchids, I could easily fit 3-5 extra plants in the space that the fan uses, also accounting for the small space where air is too strong. A fan may malfunction, crash with a growing leaf, and require maintenance yet it is still a vital part of every orchidarium. I want to search for alternatives that make use of electronics to replace a fan and induce airflow in clever ways.

Orchids and air

Vascular plants (most plants) have small apertures on the surfaces of their leaves called stomata. These structures can regulate the flow of gases. They allow CO2 to flow into the plant, O2 out and water vapour in and out of it. Orchids have less stomata than ground plants due to their slower metabolism and because they are epiphytes. Living on trees means that exposed roots may dry much faster than if they were buried in the dirt. For this and many other complex reasons, Orchids have a lower stomata density to limit water loss in their thicker leaves. Being the most species-rich family of flowering plants they have adapted to environmental conditions that require airflow needs. Orchids have less stomata and need more air, however more air may dry the roots and vegetative parts to a damaging extent. Orchid species have a “day and night” metabolism meaning some have their stomata closed during the day, others close them at night and others always keep them open. This means that there is no optimized solution where airflow can be cut at some point in the day to prevent drying the plants excessively. Orchids need 24/7 air but in general, night or (CAM) metabolism plants require less air so it can be reduced at night. This is key to being able to grow both groups of orchids in the same confined space. Air movement in closed spaces may also help to bring CO2 and O2 for the respective metabolic phase or remove H2O to help with temperature regulation.

Open stomata on Phalaenopsis

Open stomata on Phalaenopsis sp. By Lauren Holden

Wind movement in nature can mean the difference between a burnt leaf and a healthy one when exposed to the sun. Light from the sun is composed of a variety of wavelengths of which many are absorbed by the leaf and converted into heat. This should not be an issue with LED, a single wavelength, or designed spectra for growing orchids. In the first orchidarium, two 1m RS LED waterproof strips provide enough light for 20+ orchids while using less than 12 watts. Even if the light was fully absorbed and converted into heat, it would work out at less than 0.5 watts per plant. Divide that further by the number of leaves on each plant and it becomes negligible.

RS LED Strips

RS provides excellent water resistant LED’s

Then, what are the options to provide air into an orchidarium?

Here is a short table with some considerations.





Reliable, low power, low noise, affordable, ok air flow distribution.

Can still generate stagnant zones, excessive air flow, and can hit leaf or finger without a guard

Air pump

Strong airflow, low-high power, can be installed outside growing space increasing space for orchids, and affordable.

Worse air flow distribution if connected with tube, needs a more sophisticated connector, not as reliable, can’t be on 24/7, can be noisy

Piezoelectric fan

Quiet, variable power, variable size, more sophisticated, good air distribution.

Extremely expensive.

Movement of orchid

Perfect airflow distribution, power can be regulated

Unclear if it affects the plant, unclear how it will affect growth, can make plant fall or damage it

IP68 Waterproof fan

RS offers a wide selection of IP68 water-resistant fans

An air pump and a fan seem the most comparable but setting up an air pump outside of the grow space along with a fitted air filter and an injection system (not to mention maintenance) is a complex task that may only mean you can add one more Orchid to your orchidarium. So, the fan is still an overall winner. Moving the orchid however, could potentially bring equal air movement to all vegetative structures without drying the tissues. It can also shake out droplets of water that have built up on the leaves of flowers making them last for longer.

The aim of this project is to develop an automatic system that can move an orchid to provide an effective airflow around the stomata for them to perform their functions depending on environmental conditions. This may lead to smaller individual grow spaces that do not need a fan.

AndresErnestoRamosRoldan1 has not written a bio yet…