Skip to content

Orchid bark

Also known as Fir bark, Pine bark chips, Orchid mix

Growing mediumDepends
Pine bark chips Photo: Luksongm MWLLOPPEE · CC0

In short

Orchid bark is coarse chips of tree bark, most often fir or pine, used as a free-draining medium for epiphytic orchids. It lets air reach the roots and drains quickly, but it slowly decomposes and needs replacing about every two years.

How it looks

Brown to reddish-brown woody chips, sold in grades from fine (seedling) to medium and coarse. Fresh bark chips are firm with clean edges; old, decomposing bark becomes darker, softer and breaks into small crumbs that hold much more water.

Signs

As bark decomposes it breaks into fine particles; when small fragments wash out of the drainage holes, it is time to repot. Healthy orchid roots in bark are white or green and firm; soggy, mushy or black roots show the mix is holding too much water.

What favours it

Bark breaks down through wood-decaying fungi, which use up nitrogen from the mix. The American Orchid Society notes fir bark holds about 80% of its weight in water and drains freely.

Prevention

  • Choose a bark grade that matches the orchid: finer for small roots and seedlings, coarser for large epiphytes.
  • Repot about every two years, or sooner when the bark has broken down.
  • Use a pot only just large enough for the root system so the bark dries between waterings.
  • Feed with a higher-nitrogen fertiliser, as the AOS suggests, because decaying bark uses up nitrogen.

Treatment

Start with the first step and move down only if the problem persists.

  1. Repot into fresh bark when the old bark is soft, crumbly or sour-smelling, trimming dead roots.
  2. If bark dries out too fast, some sphagnum moss can be added; the AOS calls it an excellent additive for helping a mix hold moisture.

Pros and cons

Pros

  • Drains quickly and keeps air around the roots, suiting epiphytic orchids.
  • Widely available; the AOS calls fir bark the most widely used potting material.
  • Can be combined with charcoal, perlite and sphagnum to tune water retention.

Cons

  • Decomposes over about two years, becoming finer and wetter.
  • Decay fungi tie up nitrogen, so plants need extra nitrogen feeding.

Look-alikes

Pine bark fines
Bark fines are much smaller particles and dust used in general potting mixes, not chunky chips.
Coconut husk chips
Husk chips are fibrous and spongy rather than woody and layered.

Typical uses

Epiphytic orchids such as Phalaenopsis, Cattleya and Dendrobium; also chunky aroid mixes.

Sources

  1. Beginner’s Series — Part 2: Media Mania Revisited — American Orchid Society
  2. Repotting Your Orchid — Clemson Home & Garden Information Center
  3. Indoor Plants – Soil Mixes — Clemson Home & Garden Information Center

Written in our own words from these sources. Check a product label before using any treatment.