From our perspective as orchids, we are not a monolithic group. Our needs are as diverse as our breathtaking forms and colors, shaped by the specific climates of our ancestral homes. However, we can provide a general framework for the conditions that allow most of us to not just survive, but to truly thrive and reward you with magnificent blooms.
Temperature dictates the pace of our lives. It governs our photosynthesis, respiration, and most importantly, the initiation of our flower spikes. We are generally categorized into three groups based on our preferred nightly temperature drops. Warm-growing types (like Phalaenopsis and Vanda) prefer nights between 65-70°F (18-21°C) and days under 85°F (29°C). Intermediate-growing types (like Cattleya and Oncidium) enjoy nights around 60-65°F (15-18°C). Cool-growing types (like Masdevallia and many Paphiopedilum) need a distinct chill, with nights between 50-55°F (10-13°C). For nearly all of us, a differential of 10-15°F (5-8°C) between day and night is absolutely critical. This temperature drop is the environmental signal that tells us the seasons are changing and it is time to stop producing leaves and start producing flowers.
Our roots are not like those of terrestrial plants. They are aerial, often exposed to air in our natural habitats, and are covered in a spongy velamen layer that absorbs water and nutrients from the humid air. The ideal relative humidity for most of us is between 50% and 70%. In low humidity (below 40%), our velamen dries out too quickly, our roots become desiccated and unable to function, and our leaves may become wrinkled and leathery. Conversely, stagnant, ultra-high humidity without air movement invites fungal and bacterial rots that can quickly destroy us. Humidity is the medium through which our specialized roots breathe and drink.
Temperature and humidity are intrinsically linked through a process vital to our well-being: transpiration. We release water vapor through pores in our leaves (stomata) to pull nutrients up through our roots and, crucially, to cool ourselves. In high temperatures, we transpire more. If the air is also very dry (low humidity), we lose water far too rapidly, leading to severe stress and dehydration. Conversely, high humidity slows transpiration, which can be problematic if combined with high temperatures, as we cannot effectively cool our tissues. Therefore, higher temperatures often require higher humidity to prevent excessive water loss, while cooler temperatures can tolerate moderately lower humidity.
Please observe us closely. We will tell you if our conditions are not right. Leathery, wrinkled, or pleated leaves are a classic sign of dehydrated roots, often caused by low humidity or insufficient watering. Failure to bloom, despite healthy green leaves, is frequently due to a lack of that essential day/night temperature differential. Bud blast (where developing flower buds yellow and fall off) can be triggered by a sudden shift in either temperature or humidity. Sunken, dark spots on leaves often indicate a fungal issue exacerbated by cold, wet conditions combined with poor air circulation.
Recreating our ideal environment is simpler than it may seem. Grouping us together naturally raises the local humidity through our collective transpiration. Placing our pots on trays filled with pebbles and water (ensuring the pot never sits *in* the water) provides evaporative moisture. A small humidifier nearby is excellent. For temperature, simply moving us to a cooler room at night, or away from heating vents and cold drafts, can often provide the necessary fluctuation. Gentle air movement from an oscillating fan is invaluable, as it prevents stagnant air, strengthens our growth, and mimics the breezes of our natural habitats, all while helping to regulate leaf surface temperature.
