What would be a correct application of GDD in gardening?

Using Growing Degree Days (GDD) in gardening is a valuable tool for tracking plant growth stages. GDD helps gardeners determine the appropriate timing for various stages of plant development, such as germination, flowering, and maturation. By calculating GDD, one can estimate when the conditions are right for specific plants to progress through their growth cycle, providing insight into when to plant, when to expect blooms, and when to harvest.

This methodology relies on temperature data, specifically the average daily temperature in relation to a base temperature required for the growth of particular crops. As plants develop differently based on temperature, utilizing GDD allows gardeners to tailor their practices based on the climatic conditions affecting their plants.

The other options, while important aspects of gardening, do not specifically relate to the use of GDD. Nutrient level measurement, soil composition analysis, and testing herbicide effectiveness focus on different aspects of plant health and management, rather than the direct tracking of plant growth stages, which is the essence of what GDD provides.