Perennial Flax (Linum sp.) Stock Plant, Vegetative Cutting, and Flowering Stem Greenhouse Production

Perennial flax ( Linum sp.) is a new horticultural crop with potential use as a cut flower (CF) and an herbaceous perennial (HP) because its blue flowers provide a rare color in ornamentals. Crop ideotypes for CF and HP perennial flax serve as guides for future testing and product development (e.g., stock plant, cutting, and liner production). The objectives of this research were to determine greenhouse parameters for vegetative cuttings and flowering stem production to provide guidelines for producers. Fifteen CF Linum ( Linum perenne , L. austriacum , L. lewisii , L. bienne ) genotypes (CF1–CF15) were tested for greenhouse production factors. In Expt. 1, cutting yield and rooting ability/stock plant were measured to determine the genotype, container size (8.9 cm or 16.5 cm), soft pinching (pinched or unpinched), number of plants per container (one, two, or three), vernalization (before or after), and plant growth regulator (0 or 200 ppm ethephon) for 22 weeks. In Expt. 2, we tested indoor production requirements for flowering stem production to inform selection, breeding, and production scheduling. We measured morphological, phenotypic, and phenological production traits/genotype using one plant per container (13.3 cm) for 27 weeks. Pinching and ethephon treatments (Expt. 1) did not increase cutting production for CF genotypes; both container sizes averaged 2 to 3 cuttings/plant/week, regardless of plant number. Genotypes differed in production, and those with significantly higher cutting quantity and percent rooting included CF8, CF10, CF12, and CF14. Growing 3 stock plants/16.5-cm container under long days (16 hours) for 6 months was a successful protocol for stock plant production. Most traits differed significantly by CF genotype in Expt. 2. Genotypes with the CF ideotype traits of early flowering, extended flowering period, higher number of flowering stems/plant, stem length, large flowers, and plant habit were CF4, CF13, and CF14. These three genotypes averaged 25 flowering stems/plant and produced the greatest technical stem lengths (42–60 cm). Of the 15 Linum genotypes tested, the best selections for cutting production were CF12 and CF14, while CF4 and CF13 had the highest flowering stem production. All four genotypes should advance in the CF flax breeding program based on alignment with the CF ideotype model and should be hybridized to combine maximum flowering stems, greatest technical stem length, and greatest flower longevity in new hybrids.