Why were true-breeding pea plants important for Mendel's experiments?

Had Mendel chosen corn or flowers or most other plants, he would not have been able to identify homozygotes and heterozygotes.





Not many other plants have such clear delineations, for example, when certain types of roses are cross-bred, say a red and a white, often, their offspring share co-dominant alleles with a phenotype that is pink. Whereas, pea plants are very simple and made only green or yellow peas (homozygotes or hetrozygotes)--no blending occurs in this plant.Why were true-breeding pea plants important for Mendel's experiments?
Mendel always started with true-breeding peas. This way the parents were ';knowns'; and nothing surprising popped up. This is one of the main reasons why Mendel was able to figure out the basic rules and laws that govern genetics.