There are three primary lighting applications in the production of floriculture crops and others grown in semi or fully controlled environments. I will discuss these applications and lighting technology options in three talks (some in collaboration with Dr. Roberto Lopez) at AmericanHort’s Production Technology Conference in Dallas, TX, on October 10. Here’s a summary and preview of the information to be presented.
Low-Intensity Lighting to Regulate Flowering
Flowering of many common ornamental crops — including bedding plants, herbaceous perennials, and potted plants — is regulated by photoperiod. When the days are naturally short, low-intensity lighting can be delivered in greenhouses to accelerate flowering of long-day plants and to inhibit flowering of short-day plants.
Keys to successfully creating long days include:
1) Delivering an intensity of at least 1 to 2 µmol·m–2·s–1 at plant height
2) Operating lamps at night for three to four hours
3) Choosing a lamp with an effective spectrum. Over the past decade, we’ve performed numerous experiments to better understand how different wavebands of light (blue, green, red, and far-red) influence flowering and plant growth. Results will be shared with participants, and the pros/cons of different lighting technologies will be presented.
Supplemental Lighting of Young Plants
In at least the northern half of the U.S., light is a limiting factor for most greenhouse crops grown during the winter and early spring. Under insufficient light, rooting is slow, branching is poor, stems are thin, and plants have few and small flowers. Therefore, an increasing number of growers are delivering supplemental lighting to increase growth, especially in the production of propagative materials such as plugs and liners.
There are many benefits to supplemental greenhouse lighting of young plants:
1) They typically root quicker, reducing the propagation time
2) The seasonal variation in plug/liner quality is reduced, resulting in more uniform plants at transplant
3) Oftentimes, finished plants flower earlier when the young plant was grown under high light
While there’s no dispute of the benefits of supplemental lighting, it is expensive to install and operate. Fortunately, supplemental lighting technologies — especially LEDs — have advanced significantly just in the last five years. Roberto and I will present research results on supplemental lighting of young plants and discuss the different lighting technology options, helping you determine what lamp type is suitable for your greenhouse operation.
Control Plant Growth with Sole-Source Lighting
There is increasing interest by growers and entrepreneurs in producing high-value specialty crops in enclosed, indoor environments. One of the many advantages of growing indoors is the ability to completely control the light spectrum, enabling the production of uniform crops with specific and desired growth characteristics. The production of uniform plants, month after month, is why the Japanese refer to this production system as a plant factory.
We will present research-based information on how the spectrum of sole-source lighting influences plant growth attributes of ornamental transplants, leafy greens, and microgreens, including leaf size and color, stem length, and flowering.