Orchids are well known for their exotic and breathtaking flowers. However, many only flower once a year while some may only flower every few years. While you wait for flowers, I’ve found orchid roots can be an intriguing part of a plant. Unlike most plants which keep their roots well and truly out of sight in the potting mix or in the ground, orchids have large, conspicuous, often colourful roots. After a rest over winter, most orchids burst into life when the weather warms or the monsoon rains arrive. A large part of this active growth is with many new roots which in turn fuel vegetative growth.
Many orchids currently available in cultivation originally grew in the wild as epiphytes (growing on other plants, usually trees) or lythophytes (growing on rock). As well as taking in moisture, the roots keep the plant firmly attached to the plant or rock it is growing on. Orchid roots have adapted to being exposed to air. Having said that, most ephiphytic orchids came by these adaptations from growing in environments high in humidity such as rainforests or places experiencing regular precipitation (rain, dew, fog or cloud).
You may have expected the word “evolve” to be used in the above paragraph. As an evolution-sceptic, I have chosen the word “adapt” as we know for a fact all living things have adapted to their environment. However, we truly don’t know if they actually gain information (evolve). The difference is adaptation is when a plant (or animal) changes to better suit its environment using existing genetic information (same may call this “micro-evolution”). In mainstream media adaptation is often wrongly implied as “evolving” (gaining new genetic information). If you agree or disagree please comment!
Back to our subject, an actively growing orchid root has a green tip as it is growing new root tissue (velamen). As a root tip matures the outside layer of velamen dies and turns white. It is possible the dead velamen helps to protect a root from drying out. When such a root absorbs moisture the velamen layer becomes transparent.
A healthy orchid is a happy orchid with green (or white) roots and when actively growing, green root tips. When things go wrong, the roots can often provide clues. A smelly, mushy root implies this plant may be over-watered or the potting mix is degraded and requires re-potting. Or it might imply that potting mix is unsuitable for that orchid. Early on in my short orchid-growing career I tried growing Cattleya in coconut husk chips. After sometime I found coconut husk chips in plastic pots retained too much water for Cattleyas and their roots rotted. However, I found coconut husk chips are well liked by Phalaenopsis, Sarcochilus and some Paphiopedilums. My Cattleyas are now growing in a mostly bark mix, with the larger plants in clay pots.
If you grow Phalaenopsis orchids you may grow them in clear pots. It is possible some orchids such as Phalaenopsis, can use their roots for photosynthesis. Hence clear pots may keep the roots happier and less likely to grow out of the pot. The other major benefit of growing in a clear pot is you (the grower) can see the roots, watch them grow, and most importantly know when the plant requires watering. If you can see the mix is moist, no need to water. If it is dry or nearly dry then its high time to water.