Answer:
crossing the plant to one you know has the recessive trait
Step-by-step explanation:
The correct procedure would be to cross the identified plant with the same plant that has the recessive trait.
The phenotypes of the progeny from the cross will give an indication of the dominance or recessive of the phenotype. If all the progeny from the cross produce the same flower color as that of the identified plant, it means the phenotype is dominant. Otherwise, it is recessive.
The procedure is called test-crossing in genetics.