Combining Close Spacing and Pinching to Increase Yields of Lisianthus Cut Flower Stems

Lisianthus (Eustoma grandiflorum) has become popular as a cut flower because of its long vase life and attractive, rose-like appearance.  Productivity has been enhanced by closer plant spacing and by extending the harvest season in a high tunnel, but increasing the number of flowering stems per plant by pinching out the main stem growing point has not been widely practiced.  In the present experiments, we compared the use of pinching at two plant populations (1.8 and 4 plants per ft²), with two cultivars (ABC 1-3 White in 2014 and Mariachi Grande 3 White in 2015, and ABC 1-3 Purple in both growing seasons). In both years, the experiments were duplicated in a high tunnel and an adjacent field.  Yield of cut stems per unit area were increased 39 percent by pinching, and 14 percent by growth in the high tunnel. Increasing the plant population boosted yield by 51 percent, and the combination of close spacing and pinching doubled stem yield from 6.8 to 13.7 per ft².  Stem length was increased 17 percent by growing the plants in the high tunnel, but not affected by the other treatments. Removal of the plants’ growing point in the vegetative stage (pinching) delayed the onset of flowering by a week, but did not affect the end of the flower production period.  The cultivars tested reacted similarly to the treatments imposed, although they differed in earliness of flowering.  Overall, stem yields were 66 percent higher in 2014 than in 2015, due in part to a harvest season three weeks longer, but those stems were 28 percent shorter.  The combination of close spacing and pinching increased stem numbers but reduced the no. of flowers and flower buds per stem to a degree that might be detrimental to marketability.