Certified Professional Horticulturist (CPH) Practice Exam

What is the major reason weeds are considered to be undesirable in the landscape?

1. They are not as pretty as other plants

2. They compete with other plants for water

3. They don't grow as well as other plants

4. They need specific growing requirements

The correct answer is: They compete with other plants for water

Weeds are considered undesirable in the landscape primarily due to their ability to compete aggressively with desirable plants for essential resources like water, light, nutrients, and space. This competition can hinder the healthy growth of ornamental plants, vegetables, or grass, often leading to reduced yields or compromised aesthetic appeal in the landscape. While aesthetic reasons, such as attractiveness, can play a role in the perception of weeds (as suggested in the first option), the primary concern among horticulturists and landscape professionals is the competition for resources that impacts the growth and survival of desired plants. The overall vitality of a garden or landscape can be significantly diminished when weeds thrive unchecked, thus emphasizing their undesirable nature in managed environments. The notion that weeds don’t grow as well or require specific growing conditions does not align with the reality, as many weeds are highly adaptable and resilient, often thriving in conditions that may not favor cultivated plants. This adaptability further contributes to their competitive advantage in ecosystems where they are present.