Answer: To allow nursery plants to transition to the outdoors.
Step-by-step explanation:
Hardening is a process in which the small seedling plants are exposed to the unprotected environment of the garden so that they develop some tolerance against those conditions. The small seedlings were earlier exposed to low water, sunlight, and wind conditions but for hardening they are kept at those areas of the garden where they experience harsh levels of these agents for a short duration and the duration is increased with routine so that plants can adapt the changes when they are planted outdoor or outside the care of garden. It is one of the gardening practices.