Increase Lisianthus Yields by Growing Plants and Pinching Stems

Perhaps lisianthus is tougher than you think, and can tolerate a little manhandling. Set up your own trial: squeeze a few more plants into your beds, knock stems back a few inches, and see if you get the same floriferous results as Chris Wien.

The tiny seed size and glacially slow seedling growth of lisianthus have encouraged many growers of this crop to avoid producing their own seedlings, and to instead purchase plugs from commercial propagators. Since plugs can be expensive, we were interested to learn whether we could increase yields by pinching the stems, and then squeezing plants into closer spacings. The increased plant costs would then be offset by harvesting more stems from our fields.

Lisianthus plugs were purchased from a commercial plant propagator in 216-count trays, arrived on May 15, and were transplanted into 72-count trays into Cornell mix artificial soil. These were allowed to grow in the greenhouse until June 4, and were then transplanted to the field. Another set was planted in the high tunnel on June 18.The plants were spaced at 9 x 9 in. in four rows, or at 6 x 6 in. in six rows on the four-foot wide bed. In each treatment, plants were pinched to about 4 nodes in the seedling stage shortly after transplanting, or were left alone.

Spacing and pinching both in-creased stem yield per unit area, but the two combined had the most positive effect, boosting the number of stems per square foot by 80% (see table). We were concerned that by crowding the plants so much, we would end up with a lot of unmarketable stems with only one flower and no buds. Therefore, we culled the “bud-less” stems in the later harvests, and calculated the “net” yield. Poor flower quality turned out not to be a problem. Plants produced stems without buds in all treatments in similar amounts, and net yield was not significantly decreased (see table). 

Stem length was not affected by spacing, but pinching stimulated it, especially at the close spacing. Pinching delayed flowering by only six days. Since the crop had a long flowering period from early August to early November, this was not considered a significant delay.

The results of this trial indicate that lisianthus can be considerably more crowded in the bed in both tunnel and field than with the 9 x 9 in. spacing we have been using, and will demonstrate significantly increased yields without hurting flower quality. The increased density can be achieved both by closer plant spacing as well as early pinching to induce more stems to form on each plant.

I gratefully acknowledge the expert help of Priscilla Thompson and Anna Enocksson in the conduct of this trial.

Photos: Lisianthus planting in the high tunnel (left) and in the field.

TREATMENT LEVELS                                 YIELD STEMS/FT.   STEM LENGTH, IN.   TOTAL NET

Spacing6×6 in.13.5                 13.1                 16                 
 9×9 in.8.98.716
 Stat. signif. *********ns
 Stat. signif. ************
Spacing x Pinching6×6 no11.510.915
 6×6 yes15.515.217
 9×9 no8.68.416
 Interact. signif. ************


Chris Wien


Chris Wien is recently retired Professor of Horticulture at Cornell University. Contact him at [email protected]