Which plant care technique involves regularly trimming for size management?

Hedging is the correct answer as it refers specifically to the practice of regularly trimming plants, particularly shrubs and hedges, to manage their size and shape. This technique not only helps maintain a neat appearance but also encourages healthy growth and can improve plant longevity by allowing for better air circulation and light penetration throughout the plant.

Thinning, while also a maintenance technique, typically involves selectively removing certain parts of a plant to reduce density or manage growth but may not focus solely on size management. Pinching is a method used mainly for promoting bushier growth in plants by removing tips or young shoots, not for overall size management. Weeding refers to the practice of removing unwanted plants and does not pertain to trimming or shaping desirable plants. Thus, hedging is the most appropriate term for the technique related to regular trimming for size control.