US: Managing photoperiod in the greenhouse

Many ornamental crops, including common bedding plants and herbaceous perennials, flower earlier under a particular photoperiod. Some crops flower earlier when the day is short, such as chrysanthemums and poinsettias. Many more ornamental crops flower when the day is long including ageratums, coreopsis, dianthus, petunias and rudbeckias. Delivering the proper photoperiod can help ensure plants are in flower in a relatively rapid and uniform manner.

Recently, a six-page bulletin was published by Purdue Extension by researchers at Purdue and Michigan State University Extension titled “Managing Photoperiod in the Greenhouse.” This resource is intended for commercial greenhouse and nursery producers who want to learn more about how to provide short or long days to promote flowering of crops. Several different strategies and lamp types to deliver low-intensity, long-day lighting are presented.

The publication is in pdf format and can be downloaded free from the MSU Floriculture website or the Education Store at Purdue.