Orchids have earned the nickname “nature’s divas” due to their exquisite beauty and high-maintenance needs. Among these high-maintenance needs is the special type of soil mix that many of them require.
Terrestrial orchids typically do best in regular soil mixes, but epiphytic and lithophytic orchids require a slightly acidic, chunky, or rocky mix that has excellent aeration and drainage.
In this guide, we’ll provide a more in-depth discussion of the best soil mix for different types of orchids and their special soil requirements to make sure you provide only the best potting mix for your beloved orchids.
Things to Consider When Choosing Soil for Orchids
Drainage Capacity
One of the main causes of death in orchids is too much moisture caused by poor drainage and overwatering. To lessen the risk of this happening, always look for soil mixes that have excellent drainage.
Regular potting mixes often retain too much moisture for orchids, so they’re not suitable for them. Only terrestrial-type orchids, like Liparis, Phaius, Macodes, and Hetaeria, would thrive in potting mixes.
If you have an epiphytic or lithophyte orchid, choose bark-based potting mixes since they provide the best drainage capacity for these types of orchids.
Aeration
Good aeration is another extremely important characteristic to look for in an orchid potting mix. Most orchids absorb nutrients from the air instead of the soil, so it’s important that their soil mix has good airflow.
Good air circulation also helps prevent the growth of pathogens and harmful microorganisms in the growing medium. These organisms can cause bacterial and fungal diseases that can be detrimental to your orchids.
Bark and perlite promote good aeration, so look for these ingredients when choosing a potting mix for your orchid.
Orchid’s Growth Habit
Orchids have different growth habits: terrestrial, epiphytic, and lithophytic. These growth habits are important when choosing a potting mix for your orchid since they dictate how orchids absorb nutrients, oxygen, and moisture.
Epiphytic Orchids
Most orchids grown at home are epiphytic, meaning they grow on surfaces other than soil, such as trees, branches, or rocks. Some popular epiphytic orchids are Cattleya, Phalaenopsis, and Catasetum orchids.
These orchids absorb moisture and nutrients from air and rain, so their potting mix should have excellent drainage and aeration. They typically do best in bark-based potting mixes since the soil retains too much moisture.
Lithophytic Orchids
RT @uluwehi_knecht: When conditions are right, rupicolous (lithophytic) orchids will grow on bare rock. Here is Cattleya briegeri growing on a volcanic rock. #orchid #orchids #plantchat pic.twitter.com/ND3MA3dgFE
— BloomIQ.com (@bloomiq) March 4, 2018
Lithophytic orchids are those that grow on rocks and absorb nutrients and moisture from rainwater and decaying plants. Lithophytic orchids that you probably know include Paphiopedilums or slipper orchids and Phragmipedium orchids.
These orchids grow best in rocky soil but can also do well in bark-based potting mixes. Like epiphytic orchids, they don’t do well in regular potting mixes.
Terrestrial Orchids
Terrestrial orchids are the most similar to most house plants since they grow in the ground. They derive nutrients and nutrients from the soil, so they’re best grown in a regular houseplant potting mix.
Look for a potting mix that’s nutrient-rich, well-draining, and well-aerated if you have a terrestrial orchid, like Erythodes, Liparis, or Macodes. Also, consider the soil’s ability to retain moisture since terrestrial orchids need soil that can hold moisture.
pH level
Even though most orchids obtain nutrients from the air, some nutrients may still be present in the growing medium, like the ones from fertilizers, that they can absorb. In order to absorb these nutrients, the soil should have the appropriate pH for the plant.
Additionally, extreme pH levels can lead to nutrient lockout, where the orchid can’t access the nutrients from the soil and air.
For most orchids, the potting mix should be slightly acidic, around the 5.5 to 6.5 pH range. This is true whether the orchid is epiphytic or terrestrial.
Components of Orchid Soil
Fine Fir Bark
this orchid bark is so cute????
— ⋆astralex⋆ (@astrallexc) May 1, 2021
if you need fine orchid bark for your soil mixes, HomePlantInspiration on etsy has exactly what you neeed ✨ pic.twitter.com/iOZSTIJ3mw
Fine fir bark promotes good aeration and drainage in potting mixes, so it’s a suitable component for an orchid-growing medium. Its small particle size allows for air circulation around roots, prevents compaction, and ensures water has space to drain away.
A fine fir bark-based potting mix is especially suitable for epiphytic orchids as it mimics their natural growing environment.
Look for fine fir barks that are about half an inch in size. This size is small enough to support the orchid but not too small that it can impede drainage and air circulation.
Perlite
Perlite is a lightweight material commonly used in potting mixes for plants, like orchids, that require good aeration and drainage. It creates air pockets in the potting mix where air and water flow freely, ensuring efficient drainage.
It’s also sterile, which is very important for orchids, which can be quite sensitive to bacteria and other pathogens.
Perlite is suitable for almost all types of orchids, whatever their growth habit is. However, you can also replace it with coarse sand or rocks if you have a lithophytic orchid.
Sphagnum Moss
Sphagnum moss comes from living sphagnum moss and is harvested from boggy or swampy environments. It’s different from peat moss, which is harvested from decomposing moss.
It has a fibrous structure and excellent water-holding capacity, so it’s often used in potting mixes that need good moisture retention ability. It can help provide orchids with a consistent supply of water without making the potting mix soggy.
Sphagnum moss also tends to be slightly acidic, which is beneficial for orchids that thrive on slightly acidic soil.
Charcoal
Charcoal can help improve the overall cleanliness of the potting mix by absorbing various toxins and impurities in the growing medium. This protects orchids from possible diseases caused by these toxins.
Additionally, charcoal can prevent salt from building up in the soil. Excess salt, typically from fertilizers, can burn your orchid’s roots and weaken its health.
Charcoal also helps improve aeration and drainage in the potting mix. This is particularly important for orchids, especially epiphytic orchids, which derive nutrients from the air.
Soil Mix Recipes for Orchids
These recipes are best for epiphytic and lithophytic orchids, as they have special soil requirements. Terrestrial orchids grow best in regular houseplant potting mixes, so you can just buy commercial potting mixes with little to no adjustments.
Recipe 1
- 5 parts fine fir bark
- 1 part perlite
- 1 part sphagnum moss
This potting mix has good aeration, drainage, and moisture retention, making it perfect for orchids, especially epiphytic orchids. It’s primarily composed of fir bark, which is quite similar to their native growing conditions.
Perlite and fine fir bark create air pockets in the potting mix where air can flow freely, and water can drain efficiently. If you have a lithophytic orchid, you can use limestone or granite rock as an alternative for perlite.
Sphagnum moss can create a more humid environment around the roots by retaining moisture, which is beneficial for most orchid species.
Recipe 2
- 4 parts fine fir bark
- 1 part charcoal
- 1 part perlite
This is another recipe that’s suitable for most types of orchids. This recipe is more suitable for those who live in humid locations since it doesn’t have a component that helps it retain moisture.
Charcoal acts as a filtering agent that can help the mix fresh. It reduces the risk of bacteria and fungi growing in the potting mix and harming the orchid.
Like in the first recipe, fir bark and perlite enhance the draining capacity and aeration within the potting mix.
Signs That Orchid Is in the Wrong Soil
Yellowing Leaves
Don't worry, I don't want to frighten you !!! Re erm Orchid; The 2 bottom leaves are slowly going yellow. I soak it for about 10 mins once a week. And those air roots are massive. Is it OK or am I killing it. Help please ✅ (The interweb makes no sense when I look there for help) pic.twitter.com/AJPH3UKfWT
— MAC Boat 🎶 🏳️🌈🧔🚢🕺⛰⛺️⛷🌻🚵🏻🎹 (@userchooser) February 13, 2020
Yellowing leaves are a common sign that the soil mix retains too much water or doesn’t drain enough. In either of these cases, excess water typically accumulates around the roots, causing them to rot.
When the root starts rotting, they won’t be able to absorb nutrients, resulting in the leaves turning yellow.
Once you start seeing yellowing leaves, inspect the roots to see if they’re rotting. If they are, it’s best to repot the orchid with a fresh potting mix that has better drainage.
Stunted Growth
Why is my orchid dying please? @awkward_orchid pic.twitter.com/din1sUCZwR
— Ali 🇵🇸 (@occasionali) May 13, 2018
Stunted growth is another sign of poor drainage and aeration in the soil or potting mix. The roots are unable to absorb nutrients from the air or soil if the orchids are terrestrial, forcing them to redirect their resources to survival instead of growth.
This can also indicate that the potting mix has become too compacted, and roots can no longer spread, resulting in stunted growth. This means the organic matter in the mix has started decaying, and the orchid needs to be repotted in a new mix.
