Orchid Potting Mediums: How To Choose The Best Mix For Thriving Houseplants

Orchids have the reputation for being difficult to grow, but the truth is, they just have different needs. Like any plant, they'll thrive if you give them the right environment – starting with the best orchid potting medium. Unlike other houseplants, most orchids don't grow in soil at all. Instead, they cling to trees or rocks in their native habitats, which is why the potting mix you choose should reflect those natural conditions.

When repotting an orchid, standard potting soil should be avoided as it is not loose enough and will hold too much moisture. If the roots are left sitting in moisture for any length of time, they will rot. Instead, orchids should be planted in a specially formulated orchid mix, made up of bark and other breathable materials to provide air and drainage. You can easily find commercial mixes or get creative and blend your own.

Understanding the specific needs of your plant is key to good orchid care, which is why it's also worth learning about the different types of orchids and how they grow. Whether you're repotting a popular Phalaenopsis or Dendrobium, or one of the rare orchid varieties, knowing your plant helps you choose the right potting medium – and sets you up for success.

Understanding Orchid Growth & Potting Needs

Most orchids can be broadly categorized as being either epiphytic or terrestrial, though a small number are semi-terrestrial or lithophytic. Each type has a different growing environment and, therefore, slightly different preferred medium.

Epiphytic orchids grow on other plants, such as trees, however, they are not parasitic. Lithophytic orchids behave in a similar way but grow on rocks. Terrestrial orchids grow in the ground, while semi-terrestrial orchids grow in leaf litter and other organic detritus.

In order to successfully raise and get blooms from a particular orchid, it is important to know in which class your plant falls so you can ensure the right orchid growing medium.

• Epiphytic and lithophytic orchids tend to form aerial roots, which don’t burrow into the ground like other plant roots but remain freely growing as they absorb water and nutrients from the air. The roots will also help the plant attach to their tree or rock. These orchids have evolved to thrive in areas with little soil and are adapted to soilless sites. They need loose media, often composed of sphagnum moss and bark.
• Terrestrial orchids can be found growing in the ground near forests, wetlands, and moist prairies. They like a damp site and thrive near streams, rivers, and other riparian sites. The soil in these areas is moist, humus-rich, and organically dense. Terrestrial orchids are tolerant of clay loam, or even heavy clay or pure peat moss.
• Semi-terrestrial orchids may be found wild on the forest floor or near cliffs. They live in damp, but not soggy, soils that are well-draining. The medium must be rich in organic matter and nutrient-dense.

Common Orchid Potting Mediums

It is a good idea to repot your orchid every one to two years or as the plant outgrows its container and the medium has broken down. Once you understand your orchid type, you can choose or create a blend of suitable organic matter to create an ideal medium for your blooming plant.

Bark-Based Mixes

Bark – usually fir or pine – is the basis for most orchid mixes. It offers superior drainage, is useful for many types of orchids, lasts quite a long time, and is ideal for epiphytes and tropical orchids. However, it will break down in a year or so, requiring replacement. It dries out quickly and does not hold much moisture. Some of the bark available will stain skin. Orchids in primarily bark-based media can get pest issues as the insects are harbored in the bark.

Sphagnum Moss

Gardeners use sphagnum moss in many ways. It is completely organic and a living plant. The moss holds water and is very airy. It is also aesthetically pleasing as it adds a natural touch to orchid displays. But it can get too soggy and requires frequent irrigation because its composition allows it to dry out quickly.

LECA

LECA is a lightweight expanded clay aggregate comprising little, round balls of clay that are used as a soil replacement. LECA provides good drainage, aeration, and can reduce the chance of root rot. It also minimizes pest issues and lasts for a long period of time. But it does not hold nor provide any nutrients for plant growth. The product is also quite expensive when compared to other soilless alternatives.

Charcoal

This is another common orchid mix component. Charcoal increases air movement, absorbs toxins, and provides good drainage. Since it absorbs toxins, it can reduce the frequency of repotting the plant. However, it can retain excess nutrients, dries out quickly, and requires frequent watering.

Perlite & Pumice

Both perlite and pumice provide excellent aeration and drainage. Perlite is less expensive but is very light, tends to compact, and can make the orchid mixture dry. Pumice stone is heavier and can hold more moisture than perlite. But it is more costly and less available.

Peat Moss & Coconut Coir

Peat moss is wonderful for orchids, but it is not sustainable. This orchid moss takes thousands of years to form. It can also dry out so completely it is hard to rehydrate the product. Coconut coir is sustainable as it is a byproduct of processing coconuts. It resists compaction, holds moisture well, and has a neutral pH. But it is a bit more expensive than peat moss and must be soaked to hydrate it.

Choosing the Right Potting Soil for Orchids

Epiphytic orchids need a blend of organic and inorganic materials. Sphagnum and peat mosses, bark, tree fern, osmunda, cork, coir, and charcoal may be found in such mixes. There may also be styrofoam, gravel, and lava rock.

Terrestrial orchid mixes may contain fine bark and peat. They can also grow well in bonsai soil. Often, some lava rock or pumice is part of the mixture.

Semi-terrestrial plants require fir bark, which mimics the organic material found in the crotches of trees where they grow naturally.

DIY Orchid Potting Mix

Bagged orchid potting mix can be expensive to buy and is often tailored towards species with thick roots – namely Phalaenopsis. However, it is easy to make your own orchid potting mix recipe that can be customized for your chosen varieties. Most orchid growers experiment with planting mixes until they get just the right blend. The orchid variety itself can dictate the ingredients in your mix.

You want a mixture that holds some moisture but isn’t soggy. It should also be loose and airy. Consider a recipe with 50% bark and additional organics to help hold some moisture and keep the mixture loose, such as 25% sphagnum moss, 15% pumice or perlite, 10% charcoal, and ½ cup of peat moss.