The onset of reproduction is an important trait and is controlled by the FT1 locus in poplar (Populus sp.). Sequence variation in this locus is not well-understood. This study's aim is to identify sequence variation in the FT1 locus in a small population of Populus deltoides with varying reproductive onset. Gene specific primers were designed to amplify FT from 14 genotypes. The sequence analysis showed 12 single nucleotide polymorphisms and four insertion-deletion sites located in introns of FT1. No connection was observed between the identified polymorphisms and variation in reproductive onset. Further DNA sequencing of the genotypes needs to be done on the promoter region of FT1 to conduct an association study to statistically assess the connection between polymorphisms and phenotypic variation in a larger population. This information is expected to help us understand the genetic basis of phenotypic variation in reproductive onset.