Here we will focus on epiphytic tropical orchids. Most orchids grown in the home are epiphytes, meaning they live in nature by clinging to trees or even stones. The roots of these plants are highly specialized organs that differ dramatically from other plant roots. An orchid generally needs water once a week during the winter and twice a week when the weather turns warm and dry. An orchid shouldn’t go longer than two to three weeks without water; it will start dying. You can water orchids with three ice cubes per week (about 1/4 cup) to keep the plant hydrated throughout the week. However, some species may have slightly different needs, so follow species guidelines more closely than generalized watering practices.
Understanding Orchid Roots
Orchid roots are surrounded by a tissue-paper-thin membrane called velamen. This multi-purpose membrane soaks up large amounts of water quickly, adheres to rough surfaces, and promotes the exchange of minerals and salts. Like an expensive water meter, orchid velamen is an excellent indicator of your plant’s water needs. Dry velamen is white or silvery, and freshly watered velamen is green or mottled (depending on the species). Learning to read your orchid roots is the best method for getting watering right. Err on the side of caution since most orchids would rather be slightly underwatered than overwatered. Orchid roots constantly kept wet will rot, and the plant will decline. Different potting media retain different amounts of water; for example, pine bark nuggets will hold moisture longer than charcoal or clay pellets. The greater the water retention, the less you need to water. Orchids can also be watered from the top or bottom. Mounted plants will need more water than unmounted plants. Standard orchid mixes include fir bark, tree fern fiber, sphagnum moss, perlite, and gravel.
How to Water Orchids in Bark or Wood Chips
Orchids are commonly potted in bark, wood chips, or a commercial orchid bark mixture. Bark initially repels water, but if you soak the pot in a container full of water, it retains the water.
How to Water Orchids in Moss
Sphagnum moss is a fine substrate that can hold water better than bark. It is a great potting medium for young orchids; but a hard medium for delicate root structures to breathe or air out. The best way to water an orchid potted in sphagnum moss is to run the entire pot under the faucet until it flows freely through the drainage holes. Avoid soaking the orchid’s water-sensitive crown (where the leaves attach to the stem).
How to Water Orchids in Other Potting Media
Other popular orchid potting media include perlite, gravel or rock, and tree fern. Each has advantages and disadvantages, such as water retention, decomposition, and root aeration properties.
Tree Fern Fiber
Tree fern is a fiber harvested from the trunks of tree ferns. It is used as a major component of orchid potting mixes. It retains water well except when it starts to decompose; then, it loses its water retention and aeration capabilities. It is not as woody as bark, though it decays similarly. Thoroughly water it like you would for a sphagnum moss mixture under a running water faucet. Let it drain completely. As the fiber dries out, it turns lighter in color. The color change and the pot’s lighter weight indicate when your orchid is ready for watering.
Perlite
Perlite, also known as sponge rock, is volcanic glass exposed to high heat. Its chemical name is sodium potassium aluminum silicate, which looks like little beads of white styrofoam. It does not decay and doesn’t leach away nutrients from plants. It also doesn’t contribute any nutrients to orchids, but the substance has excellent water retention and aeration properties. It’s also a very easy medium to find in nurseries, garden centers, and online. When using perlite as the sole planting medium, it works best with a reservoir or self-watering pot. This pot is beneficial for ensuring your orchid has ample water. Simply refill the reservoir when it appears empty.
Gravel, Rocks, Charcoal, or Clay Pellets
Gravel, rock, charcoal, or clay pellets do not break down like woody media, and they are reusable after sterilization. However, these media do not retain water well, and the plant and its roots can dry out quickly. When using rocks or gravel-like potting media as a substrate, water the plant on schedule once a week to ensure its roots do not desiccate. To water it, place the orchid pot under a faucet of lukewarm slow-running water until water flows from the holes. Allow the plant to drain for 15 minutes.
Best Practices
As previously mentioned, it’s hard to generalize. It’s always best to follow the rules for your particular plant. There are, however, some best practices that will greatly increase your chances of success.
Water thoroughly. When you water the plant, do it as if you mean it. Different growers have different rules, but many professional growers turn on their sprinklers for eight or more minutes. Successful home-growers sometimes dunk their plants, pots, and all, into a bucket or sink of water. Some varieties, such as vandas, can be left floating in water for a surprisingly long time. The idea is to make sure the velamen is completely saturated. You want tiny droplets hanging on the roots after watering. This means the plant is completely hydrated.
Check your water. For a long time, serious growers insisted that orchids could only be watered with rainwater. Nowadays, most people just use tap water, and this is fine. However, be aware that treated water may have higher salt content, and some water is high in calcium. If you see deposits forming on your plants, you should seek out a new water source.When in doubt, don’t. If you’re not sure if you should water your orchid or not, hold off. Again, there are some species this won’t work for, for instance, paphiopedilum and phragmipedium. By the time they look thirsty, they should have been watered yesterday. But most potted epiphytic orchids would rather be on the dry side than overwatered.
Common Mistakes
Orchids are tropical plants, right? So they like lots of water, right? The answer is sort of. Many popular orchids are tropical plants, but they are tropical plants that live in trees. In their natural habitat, they are exposed to drenching rains that may last hours or even days, but many species are also adapted to a dry period where little rain might fall for weeks. When growing orchids in your home, it’s highly unlikely you’re duplicating the canopy environment of a tropical forest with the right airflow, humidity, and light levels. So, keeping this in mind, here are the most common mistakes people make when watering orchids:
Watering too often: Orchid plants should never be allowed to sit in still water. In many cases, the plant should completely dry between waterings. Watering at night: No matter what kind of orchid you grow, always water in the morning. Always. Nighttime watering allows water to stagnate in the growing tips of phalaenopsis orchids or the flower sheaths of Cattleyas. This encourages bacterial and fungal diseases. Orchid plants should be dry heading into the night. Ignoring the plant’s cues: Orchids are pretty good about telling you what they need. During the growing season, pseudobulbs should be fat and plump, and fleshy leaves should be held up off the potting media and thick. Some deciduous orchids might shrivel during the winter. This is fine. Know what you’re growing.
Factors That Affect Watering
If only there was an easy guide or a little water fairy that hovered over your plants and told you exactly when and how much to water. Unfortunately, there isn’t. But that is one of the satisfying reasons people grow orchids. It’s all about balance and instinct—and plenty of patience. Here are some of the factors you need to consider when developing a watering schedule:
Species: Make sure you are familiar with your particular species and follow specific rules for its care. Different orchids can have very different watering requirements, and it can be very challenging to have a mixed collection without overwatering or underwatering at least some of your plants. It’s best to start with just one or two favorite varieties. Temperature: The higher the temperature, the greater the need for water, in general. Humidity: In general, the greater the ambient humidity, the less need there is for watering. Humidity is closely related to the kind of potting media you are using. Many home-growers keep their pots in a tray of pebbles filled with water to increase local humidity. Airflow: Don’t be afraid of a little airflow. Orchids like plenty of fresh air, both around the roots (for mounted plants) and leaves. But greater airflow tends to dry them out quicker, so you’ll need to increase watering.
