Effects of Photoperiod Treatments on Stock Plants and Cutting Rooting of Callirhoe involucrata James E. Klett and Ronda Koski Colorado State University Department of Horticulture and LA Production of attractive and desirable plants, native to the plains and prairies of central North America, can sometimes be limited due to problems associated with successful rooting of vegetative cuttings. Species that have a long period of bloom can be challenging to vegetatively propagate during the growing season, because sufficient juvenile (vegetatively) growth is necessary for high-quality cuttings. Callirhoe involucrata (winecups) is a native herbaceous perennial with sprawling stems, palmately divided leaves, and dark pink flowers that creates a long lasting, colorful groundcover in landscapes with limited or no supplemental irrigation. Winecups can be difficult to propagate due to seed dormancy and poor rooting of vegetative cuttings. Manipulating the growing conditions of stock plants to suppress reproductive growth may improve rooting success of vegetative cuttings. Based on previous research at Colorado State University with other ornamental perennials and programmed photoperiods, winecups were grown under three programmed photoperiods to determine if a particular photoperiod could be used to suppress reproductive growth and promote vegetative growth. The research was replicated three times, all conducted in a similar fashion, but at different times of the year. Results indicate that plants grown under 10-hour light and 8-hour light photoperiods remained vegetative longer when compared to plants grown under 12-hour photoperiod. Plants grown under 12-hour photoperiods had greater mean ending dry weight when compared to plants grown under 10 hour and 8-hour photoperiods. Cuttings harvested from plants grown under 8-hour photoperiod had higher percent rooting and greater number of roots per cutting when compared to vegetative cuttings harvested from plants grown under 12-hour photoperiod. Based on these research findings, plant propagators may be able to increase production of winecups by growing stock plants under 8-hour photoperiod.
