Step 1: Understanding the Concept:
The question asks for the name of the pre-reproductive stage in a plant's life cycle.
Step 2: Detailed Explanation:
The life cycle of a plant is typically divided into two main stages:
\[\begin{array}{rl} \bullet & \text{Juvenile phase (or Vegetative phase): This is the initial period of growth after germination, during which the plant is physiologically immature and cannot reproduce sexually (i.e., it cannot produce flowers and fruits). Its energy is focused on developing roots, stems, and leaves. } \\ \bullet & \text{Reproductive phase (or Adult/Mature phase): After the juvenile phase, the plant becomes capable of sexual reproduction. This phase is often marked by the onset of flowering. The flowering phase is part of the broader reproductive phase. } \\ \end{array}\]
The "precocious phase" is not a standard term; "precocious" means developing unusually early, which is an exception, not the rule.
The question describes the stage before the plant can reproduce, which is the juvenile phase.
Step 3: Final Answer:
The stage of growth before a plant can reproduce sexually is known as the Juvenile phase.