Masdevallia is a large, tropical, Western Hemisphere genus of the orchid family (Orchidaceae). One way that these plants are classified is by the temperature range in which they thrive. The three main temperature categories are cool, intermediate and warm, with subcategories such as cool-to-intermediate and intermediate-to-warm.
Temperature ranges are further split into nighttime and daytime ranges. Cool growing species require a range of 45 to 53 degrees F (7 to 12 C) at night and 50 to 63 degrees F (10 to 17 C) during the day. When daytime temperatures are hotter, appropriately cool nighttime temperatures help to regulate heat stress.
If you live in a naturally moist, mostly cool environment, such as in San Francisco and along the Northern California coast, cool Masdevallias can live outside in the shade of a lath house almost all year long. However, backup plans for cooling and humidifying are necessary for unexpected hot spells. Growing Masdevallias in areas with colder winters and hotter summers requires greenhouse and indoor environments with well-regulated growing conditions.
It may seem counter-intuitive, but one way to regulate heat stress is to minimize watering so roots stay drier. Damp roots can rot when temperatures are high. Other strategies for conquering heat stress include reducing light levels, misting plants and providing more air movement.
Flowers by the Sea sells a number of cool-growing Masdevallias, including ones that also do well in an intermediate temperature range. That's why you'll find some of the plants listed here in our intermediate queue.