| In general you repot for two reasons. Either the growing medium is too old and needs to be replaced or the plant is so large it must be repotted.
Bark and even sphagnum deteriorates and must be replaced periodically. With Phals that is about every three years for bark and in sphagnum it could be 3-4 years. You would repace a little more often for other species, but it is the condition of the medium that is the controling issue.
I know a commercial nursery that uses Physan (a contact fungicde) every week as general control. This prevents the growth of algae and as a side effect it kills most of the bacteria that decomposes bark. As a result he does not need to repot until about 5-6 years. This is not something I recommend for hobbist and I do not do it myself.
Phals take a long time to outgrow a pot in a home. Unless the plant was too large when you bought it, it can stay where it is for a couple of years. A good grower always ships his plants in fresh medium that will last 1-2 years.
Plastic vs clay is not an issue for commercial growers. Clay is too heavy to ship so we must use plastic. Plastic holds water longer, while clay draws the water more evenly throughout the pot as it dries. Phals like to be slightly moist all the time so plastic is easier if you forget to water, whereas clay is more forgiving if you tend to over water.
The same with bark vs sphagnum. Sphagnum holds more water and is best if you are inconsistent on watering while bark dries faster and safer if you tend to overwater.
All this advice applies to phals and care of cattleyas and oncidium types will be different.
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jerry  |