What Is Velamen? The Spongy Coating on Orchid Roots
Velamen is the spongy coating on the roots of many orchids that grow on trees. It wraps the aerial roots that hang in the air or cling to bark.
The short answer
NC State Extension notes aerial roots absorb water from the air plus help orchids anchor to a surface. Moth orchid roots can photosynthesize, giving them a green color. Penn State advises a bark mix that drains fast but holds some water. Let the mix dry a little between waterings.
What does velamen do?
The NC State Gardener Handbook notes aerial roots take in water from the air. UC Botanical Garden at Berkeley notes the velamen is made of dead cells that soak up rain fast, then slowly pass water to the living root. UF IFAS notes most orchids are epiphytes that need special media such as fir bark or tree fern fiber.
| Root look | Likely state | Action |
|---|---|---|
| Green plus firm | Recently watered | Wait to water |
| Pale plus firm | Drying out | Water soon |
| Soft plus dark | Soggy mix | Trim plus repot |
Source: NC State plus UF IFAS Extension.
Why do orchid roots change color?
NC State notes moth orchid roots make chlorophyll, so they look green. That is why growers use clear pots. Penn State notes roots may grow into the air and misting is optional.
What does damaged velamen look like?
NC State notes wrinkled leaves can mean damaged roots, often rotted by soggy mix. UF IFAS advises cutting off dead roots at repotting.
How to: step by step
- Look at the roots of a moth orchid.
- Note root color when the mix is dry.
- Water plus watch for green.
- Press lightly to find firm roots.
- Spot soft roots that need trimming.
- Let the mix dry a little before you water again.
Troubleshooting
Wrinkled leaves: dry mix or root rot. Check roots first.
Roots in the air: normal growth. Penn State notes misting is optional.
Soft dark roots: wet mix. Repot in bark.
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Sources
- Orchids as houseplants, Penn State Extension
- Orchids, UF IFAS Gardening Solutions
- NC State Extension Gardener Plant Toolbox, Phalaenopsis (moth orchid)
- Extension Gardener Handbook, chapter 3: botany, NC State Extension
- Nature’s savings and loan: how epiphytes survive without soil, UC Botanical Garden at Berkeley
FAQ
Why are orchid roots green?
NC State Extension notes moth orchid roots can photosynthesize, giving them a green color. Clear plastic pots are often used.
When should orchid roots be trimmed?
UF IFAS advises removing old media plus any dead or diseased roots when you repot an orchid.
Why do orchid roots grow in the air?
The NC State Gardener Handbook notes orchids often form aerial roots. They absorb water from the air plus help with anchorage.
How often should orchids be watered?
NC State notes mature moth orchids need water about once a week, more in summer heat. Let the mix dry some between waterings.
What mix suits orchid roots?
Penn State advises a mix that drains fast but holds some water. Bark based media meet both needs.
