What does "hardening off" refer to in plant culture?

"Hardening off" refers to the process of gradually acclimating plants to outdoor conditions. This important horticultural practice helps plants adapt from the controlled environment of a greenhouse or indoor setting to the more variable conditions outdoors, which can include changes in temperature, humidity, light exposure, and wind.

The gradual acclimatization process typically involves exposing the plants to outdoor conditions for increasing periods over several days or weeks, starting with just a few hours each day. This allows the plants' new growth to toughen and become more resilient. As a result, they are less likely to experience shock or stress when eventually moved outdoors for planting or as part of garden arrangements.

The other options do not accurately describe the process: instantly acclimating plants would expose them abruptly to outdoor stresses without preparing them sufficiently, while removing weeds and applying fertilizer are unrelated gardening tasks that do not address acclimatization.