Nearly everyone knows the simple rule that house plants should be repotted once a year or every two years to adjust fresh soil with so much needed macro and micronutrients. And that’s why so much people asking – how often should I repot an orchid? When to repot an orchid? What’s the best time to do this? This is not a secret that orchids actually are rather different from common house plants and do not grow in standard soil mixes, also they have different ecology and physiology, and that’s why standard instructions about common houseplants repotting don’t work with orchids.
The first think to consider is that orchids are mostly epiphytic. Rather slow-growing plants with thick layer of velamen on its roots. That’s why orchids actually react not very well on repotting – if roots are damaged it is very bad for an orchid because it is not quite fast the orchid will grow new roots. Because of thick velamen layer orchid roots are damaged very easily, so it is good to repot orchid not very frequent. Frequency of orchid repotting depends on which substrate you use. Orchid substrates should be well-drained, with good aeration so air go freely to roots and with rather low water capacity to insure that the roots dry freely. Organic substrates such as bark and cocoa chips are rather good for this task and they are natural but they are actually decompose and lose their low water capacity and become soggy. So, orchid has to be repotted when its substrate is no longer well drained, because such substrate do not dry for longer periods of time, which is not good for epiphytic roots – without air and with too much water roots die and rot. Inorganic substrates such as clay pellets, lava rock and organic but not biodegradable such as epiweb do not decompose, so you do not need to repot orchid at all – only if it is too much roots and pot is destroyed by roots mass. So, the rule is simple – if substrate is not decomposed, if it dries quickly and air freely goes through it, don’t repot your orchids. Orchids do not like to be overrepotted, so repot it only if substrate is decomposed or the pot is broken or far too small to entire plant.
The other factor that you should consider is the life cycle of the orchid you’re going to repot. When a new growth of root system has just begun, it is the best time for repotting. This time is the most proper, firstly because roots aren’t too long yet, so it’s easy to avoid root damage, and secondly because you should avoid repotting dormant plants. In most cases the most suitable time is in the spring, right after dormancy. For orchids without a rest period, such as Phalaenopsis, the best time to repot comes right after flowering.