Orchids often enter periods of dormancy - when the plant goes into what some call a 'rest' period, and shows no signs of growth (either above or below ground). The triggers which cause the plants to enter and emerge from the dormant state are as yet unknown - though it's believed that symbiotic fungi may play a part. Further, the evolutionary pressures which have presumably enabled this strategy are unclear.
[…] vegetative dormancy is often associated with plant stress and may be important for survival However, for vegetative dormancy to be a successful strategy, plants must have higher survival or, at least not substantially less growth, than they would have not entering dormancy. What triggers orchids to enter or emerge from dormancy is unknown, but it may be related to plant nutritional status which, in turn, may be related to environmental stress."
Source :Symbiont abundance can affect host plant population dynamics American Journal of Botany, Jan 2017.