What do growing degree-days, also referred to as heat units, primarily measure in relation to plant growth?

Growing degree-days, or heat units, are primarily used to quantify the amount of heat that accumulates over time to assess plant growth and development. This measurement specifically tracks temperature impacts on plant processes, such as germination, flowering, and maturation.

The concept is based on the understanding that plants require a certain amount of warmth to progress through their growth stages. By calculating growing degree-days, farmers and horticulturists can make informed decisions about planting schedules, pest control, and harvesting times, as these activities often align with the developmental phases of crops that are influenced by temperature.

In this context, while humidity levels, soil composition, and air pressure changes do play roles in agricultural practices, they are not the primary focus of growing degree-days. Instead, the essential factor here is the temperature, which directly influences the growth rate and development of plants, thereby making temperature impacts the central aspect of this measurement.