TheNaturePlanet

"I’ve been carefully taking care of my orchid and just changed the sphagnum moss, but why has moss grown in just a few days? Is the moss going bad?" Sphagnum moss and moss are completely different things, with very different uses and effects on orchids.

Sphagnum moss is a great partner for growing orchids. The sphagnum moss we buy is dry, and when soaked, it becomes soft and is usually light green or yellow-brown in color. It feels like a sponge and has strong water retention and absorption abilities. It’s harvested, processed, and dried specifically for use as orchid growing medium. It can secure the orchid’s roots, slowly release water, keeping the aerial roots moist but not waterlogged, and it’s also breathable, allowing the roots to breathe comfortably. When repotting, we wrap sphagnum moss around the orchid’s roots or lay it on top of the pot to help the orchid “drink water” without suffocating the roots.

Now, moss, on the other hand, is often an "uninvited guest." It’s typically a fresh green, thin layer that grows on the surface of the pot or on the pot walls, sometimes creeping into the gaps of the sphagnum moss. It feels slippery to the touch. Moss isn’t a growing medium we use intentionally. It forms when the environment is too humid and has insufficient light. The spores of moss in the air fall onto the surface of the pot and gradually spread. In simple terms, sphagnum moss is “invited to help,” while moss is “self-invited.” They are fundamentally different, so don’t mix them up.

So, does moss growing in the pot affect the orchid? Don’t worry, moss itself doesn’t harm the plant—it doesn’t eat the orchid’s roots or compete for nutrients. But if left unchecked, problems can arise.

The first issue is that it makes it hard to judge when to water. When growing orchids, we usually look for the sphagnum moss on top of the pot to turn white and dry before watering. But with a layer of moss, it’s hard to see if the sphagnum moss underneath is dry or wet. You might think it’s dry and not water it, causing the roots to wrinkle from lack of moisture. Or you might think it’s time to water, but the moss-covered surface is still wet, leading to root rot because of over-watering.

The second problem is that moss blocks airflow. It acts like a small plastic film over the pot, preventing the moisture inside the growing medium from evaporating. This can lead to mold growth on the sphagnum moss or bark. Orchids' aerial roots need good airflow, and if they’re trapped in a damp, non-breathable environment, they’ll turn from white to brown and begin to rot.

So, what should you do if moss has already grown? If it’s just a few small patches, use a small tweezer to gently remove them without damaging the nearby aerial roots. Afterward, move the pot to a spot where it can get indirect light, like near a window, for 2-3 hours a day. The light will help prevent the moss from growing back. Also, adjust your watering routine—water only when the growing medium 2 cm below the surface is dry, and always drain any excess water from the tray after watering to avoid leaving the pot sitting in water.

If the moss has covered the entire surface of the pot or even worked its way into the growing medium, it’s time to repot. Gently remove the orchid from the pot, shake off the old sphagnum moss, and rinse the roots with clean water. Check for rotten roots (which will be brown and soft), and trim them with sterilized scissors. Soak the roots in a fungicide solution for 10 minutes, let them dry, and then repot with fresh sphagnum moss. Don’t pack the new moss too tightly—leave some gaps for airflow.

When growing orchids, make sure to use proper orchid-grade sphagnum moss, promptly deal with any moss growth, provide good ventilation, and avoid over-watering. By keeping the environment from becoming too damp, your orchids will thrive and bloom abundantly!