Described herein are compositions, including RNAi and/or CRISPR constructs, for modifying one or more Flowering Locus T (FT) genes in a plant and methods of using the compositions for producing plants having suppressed or delayed flowering time. In some embodiments, the plant is a Saccharum plant. The approach used herein involves methods for decreasing expression of one or more Flowering Locus T (FT) genes by RNAi inhibition or CRISPR/Cas9 targeted mutagenesis that results in suppressed or delayed flowering in Saccharum plants, such as sugarcane or energycane. Target genes were isolated from the sugarcane and energycane cultivar and a conserved sequence between these cultivars and closely related species was chosen to design intron-hairpin RNA constructs for RNAi suppression or sgRNA expression constructs for targeted mutagenesis. Recombinant DNA vectors were introduced into sugarcane by biolistic gene transfer and transgenic plants were regenerated and selected, vegetatively propagated for replicated field testing. These genetically modified plants produce significantly elevated biomass and recoverable sugar yield under replicated field conditions relative to a similar plant in which the FT4, FT8, and/or FT10 gene have not been disrupted, when grown under the same conditions.