We developed two leafy spurge bacterial artificial chromosome (BAC)libraries that together represent approximately 5× coverage of the leafyspurge genome. The BAC libraries have an average insert size ofapproximately 143 kb, and copies of the library and filters forhybridization-based screening are publicly available through the ArizonaGenomics Institute. These libraries were used to clone full-length genomiccopies of an AP2/ERF transcription factor of the A4subfamily of DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEINS (DREB) known to be differentially expressed in crown buds ofleafy spurge during endodormancy, a DORMANCY ASSOCIATED MADS-BOX (DAM) gene, and several FLOWERING LOCUS T (FT) genes.Sequencing of these BAC clones revealed the presence of multiple FT genes in leafy spurge. Sequencing also providedevidence that two different DAM transcripts expressed incrown buds of leafy spurge during endo- and eco-dormancy result fromalternate splicing of a single DAM gene. Sequence data fromthe FT promoters was used to identify several conservedelements previously recognized in Arabidopsis, as well as potential noveltranscription factor binding sites that may regulate FT.These leafy spurge BAC libraries represent a new genomics-based tool thatcomplements existing genomics resources for the study of plant growth anddevelopment in this model perennial weed. Furthermore, phylogeneticfootprinting using genes identified with this resource demonstrate theusefulness of studying weedy species to further our general knowledge ofagriculturally important genes.