What does ‘hardening off’ plants mean?

'Hardening off' refers to the process of gradually acclimating seedlings to outdoor conditions. This practice is crucial for ensuring that young plants, which have typically been grown indoors or in a greenhouse, can adapt to the more variable environment outside without suffering from shock. During this process, plants are exposed to increasing amounts of sunlight, wind, and fluctuating temperatures over a period of time. This gradual introduction helps strengthen the plants’ physiological responses and increases their resilience to environmental stresses, ultimately leading to better survival rates and growth once planted in their final outdoor locations.

The other options describe practices that are unrelated to the hardening off process, focusing instead on different aspects of plant care or maintenance. Pruning plants heavily, for example, pertains to trimming and training plants, and planting in colder climates does not specifically involve any acclimatization process. Similarly, enhancing plant growth with fertilizer addresses nutrient management rather than transitioning plants to outdoor conditions. Each of these practices serves distinct purposes within horticulture but does not equate to the essential hardening off procedure.