Step 1: Define incomplete dominance.
Incomplete dominance occurs when neither allele is completely dominant over the other, resulting in a blended phenotype.
Step 2: Identify the flower with incomplete dominance.
- Snapdragon: A classic example of incomplete dominance where red and white flowers produce pink offspring.
- Rose: Exhibits complete dominance.
- Poppy: Also shows complete dominance in color traits.
- Lily: Shows complete dominance.
Step 3: Conclude.
Snapdragon is the flower that exhibits incomplete dominance.
Final Answer:
\[
\boxed{\text{Snapdragon}}
\]