Deciding on a Potting Mix for Orchids

By Steven A. Frowine and National Gardening Association from Orchids For Dummies

The right potting mix for orchids provides plenty of drainage, air circulation, or moisture — depending on the needs of your particular orchid. Orchid mixes consist of a variety of potting materials, each of which has its pros and cons. You can mix your own blend from the recipes below, or you can buy ready-made orchid mixes.

Knowing your potting material options

The phrase potting material isn't just a fancy way of saying dirt. Potting materials can consist of gravel, dried plant fibers, bark, and more. You won't find potting soil in orchid mixes, because most orchids have roots that need more air space than soil can provide. Orchids also need potting material that drains rapidly and at the same time retains moisture. Because orchids usually go at least a year, and many times longer, between repotting, they also need materials that are slow to decompose.

No single potting material works best for every orchid or orchid grower. The following table shows some of the most common potting materials used, along with some of their pros and cons.

Pros and Cons of Potting Materials for Orchids
Potting Material	Pros	Cons
Aliflor	Doesn't decompose; provides good aeration	Heavy
Coco husk chunks	Retains moisture while also providing sufficient air; slower to decompose than bark	Must be rinsed thoroughly to remove any salt residue; smaller grades may retain too much moisture
Coco husk fiber	Retains water well; decomposes slowly	Does not drain as well as bark or coco husk chunks
Fir bark	Easy to obtain; inexpensive; available in many grades (sizes)	Can be difficult to wet; decomposes relatively quickly
Gravel	Drains well; inexpensive	Heavy; holds no nutrients
Hardwood charcoal	Very slow to decompose; absorbs contaminants	Holds very little moisture; can be dusty to handle
Lava rock	Never decomposes; drains well	Heavy
Osmunda fiber	Retains moisture; slow to break down	Very expensive; hard to find
Perlite (sponge rock)	Lightweight; provides good aeration and water retention; inexpensive	Retains too much water if used alone
Redwood bark	Lasts longer than fir bark	Hard to find
Sphagnum moss	Retains water and air; readily available	Can retain too much water if packed tightly in the pot or after it starts to decompose
Styrofoam peanuts	Inexpensive; readily available; doesn't decompose; rapid draining	Should not be used alone because doesn't retain water or nutrients; best used as drainage in bottoms of pots; can be too light for top-heavy plants
Tree fern fiber	Rapidly draining; slow to decompose	Expensive; low water retention

Make your own orchid mix

Following are recipes for two basic mixes that suit most orchids. The growing mixes are based on the texture or particle size of the mix, which is connected to the size of the orchid roots and their need for water retention.

Fine mix

This mix works well for smaller plants of all types of orchids, slipper orchids, most oncidiums, miltonias, and any other orchids with small roots that like to stay on the damp side:

4 parts fine-grade fir bark or fine-grade coco husk chips or redwood bark

1 part fine charcoal

1 part horticultural-grade perlite or small-grade Aliflor

Medium mix

This is your middle-of-the-road mix. If you aren't sure which mix to use, try this one. This mix is also good for cattleyas, phalaenopsis, and most mature orchids:

4 parts medium-grade fir bark or medium-grade coco husk chunks

1 part medium charcoal

1 part horticultural-grade perlite or medium-grade Aliflor

If you'd rather just buy your mix ready-made, prepared potting mixes are readily available from most places that sell orchids, including home-improvement stores. Most mixes contain fir bark, perlite, charcoal, and sometimes some peat moss and are suitable for most orchids.