Propagating Floriculture Crops Under Sole-Source Lighting

September 18, 2018
Leontiene van Genuchten

In the last 10 years, many companies have sprung up to grow herbs and greens in climate-controlled vertical farm or city farm facilities which are daylight-free. As a plant specialist for floriculture with Signify(formerly known as Philips Lighting), I’ve watched these developments with great interest. But I have wondered if a vertical farm can also benefit cultivation of young plants from floriculture crops. 

Cultivating floriculture crops without daylight

Growing plants under daylight is the standard practice in conventional greenhouses. But as the popularity of vertical farms has increased, we as plant specialists have been asking ourselves if it is possible to grow floriculture crops without the influence of daylight. Why would growers want to do this? In a greenhouse, the sun affects both the amount of light that the plant receives as well as the temperature and humidity of the growing environment. A controlled environment removes the influence of daylight on the plant’s growth. This would allow growers to strictly control the growing climate to best meet the needs of each plant throughout the day.

Cultivating in a controlled environment also allows growers to optimize other factors, like plant quality and growth speed, and reduce water usage. Since fewer diseases and bacteria come into the controlled environment, vertical farming can also help stop the use of insecticides and fungicides.

Set-up of floriculture trial

These benefits prompted us to conduct a floriculture trial in our climate-controlled test facility at BrightBox in Venlo, The Netherlands. Most of the requests we receive are from growers of young plants, so we ran a trial on the propagation phase of flowers. We chose a wide range of annual and perennial plants, including begonias, petunias, calibrachoas, dianthus, gerberas, celosias, alternatheras and impatiens.

For this trial, we translated the cultivation conditions of a greenhouse to a climate-controlled environment and added the experience of our colleague City Farm plant specialists. Light levels were chosen based on the reference greenhouse environment with daylight, as well as scientific literature and the experience of growers. The light spectra used in the test were aligned with a number of growers to meet their quality standards for the different varieties of flowers. Growth speed is one requirement from growers, but good plant quality is the first priority. In this case, a plant is considered good if it has a compact shape, enough leaves and branches and a good root system. In addition, a good plant should be able to quickly establish roots and bloom as it moves to its next growth phases.

By drawing upon our experiences and the scientific literature we were able to extract enough insights to develop light recipes that would produce these plant characteristics. For example, many plants react to a higher amount of blue light by becoming more compact. The length of the internodes becomes shorter. Some plants benefit from far red light by germinating faster and developing stronger roots, while other react by bolting and drooping.

Read the results of our trial on the Philips horticulture blog

Leontiene van Genuchten is plant specialist at Signify (formerly known as Philips Lighting).