The question of how much water an orchid needs per week is best answered by understanding that a specific weekly volume is not a reliable measure. Most popular orchids are epiphytes, meaning they naturally grow attached to trees or rocks, not in soil. Their roots are adapted to receive bursts of water followed by periods of drying. The correct approach is to determine when the plant is ready for water, not when the calendar dictates it.
Why Fixed Weekly Watering Schedules Fail
Adhering to a fixed watering schedule, such as once a week, often leads to the most common cause of orchid death: root rot. Orchids require excellent air circulation around their roots, and constant moisture suffocates them. This creates an environment where fungal and bacterial pathogens thrive, preventing the plant from absorbing water and nutrients.
Instead of relying on a calendar, look for physical cues that signal the potting medium is nearly dry. The most reliable method is visually checking the roots, particularly for common orchids like the Phalaenopsis (Moth Orchid) grown in transparent pots. When the roots are fully hydrated, the specialized tissue covering them, called velamen, appears plump and green. As the velamen dries out, it turns a silvery-white or gray color, indicating the orchid is ready to be watered.
If the roots are not visible, perform a weight test by lifting the pot to learn the difference between its heavy, watered state and its light, dry state. Another simple check is the finger or skewer test. Insert a wooden skewer or your finger about one inch into the potting mix; if it comes out dry, it is time to water. Waiting for these signs shifts the focus from an arbitrary schedule to the plant’s actual moisture needs.
Key Factors That Determine Water Needs
The rate at which an orchid dries out, and therefore the frequency of watering, is highly dependent on several environmental and physical variables. The type of potting medium significantly impacts water retention. Fir bark chips are coarse and hold less water, drying out quickly and often requiring watering every four to ten days. Sphagnum moss retains moisture much longer, meaning plants potted in moss may only need water every seven to ten days or less frequently.
Environmental conditions in the home also influence the rate of evaporation. High temperatures speed up the drying process, requiring more frequent watering than cooler conditions. Low humidity and strong air circulation, such as from an air conditioner or fan, will also cause the potting medium to dry out faster.
The specific species of orchid also plays a role in its tolerance for dryness. Orchids with thickened water-storing stems, known as pseudobulbs, like Cattleya and Oncidium, can tolerate drying out completely between waterings. Conversely, orchids that lack these water storage organs, such as Phalaenopsis and some Vanda species, should be watered just before the medium becomes completely dry. Understanding these differences helps customize the frequency.
Proper Technique for Watering Orchids
Once the visual and physical checks confirm the orchid is ready for water, the delivery technique is crucial. The best method is to water copiously until the potting medium is fully saturated. For orchids potted in bark, the most effective way to ensure saturation is the soaking method.
This technique involves placing the plant, still in its inner grower pot, into a container and filling it with room-temperature water halfway up the pot. Allowing the orchid to soak for 15 to 20 minutes ensures the bark absorbs sufficient moisture. This saturation process should be followed by a thorough flushing, allowing water to run freely through the pot’s drainage holes.
Flushing washes away accumulated fertilizer salts and minerals from the potting medium. After soaking and flushing, let the pot drain completely, ensuring no water remains in the decorative cachepot or saucer. Leaving the orchid sitting in standing water will quickly negate the benefits of proper watering and lead to root suffocation. Using filtered, distilled, or reverse osmosis water is recommended if tap water contains high levels of chlorine or dissolved salts.