Science & Technology

In the Summer 2026 issue of the UCNFA Newsletter, the Featured Article provides interviews with three long term fixtures in Florida’s tree grades and standards program as momentum builds around similar efforts in California. The first article in Science to the Grower explains how to measure evapotranspiration (ET) and use ET values in greenhouse settings. Our second article in Science to the Grower explains how supplemental lighting can improve crop uniformity and shorten production cycles.

Evaporation is the process by which water turns into vapor from a surface. After an irrigation or precipitation event, water evaporates from the growing media, soil, and wet plant surfaces. Conversely, transpiration refers to water traveling through a plant’s roots and vascular system and turning into vapor inside the leaf mesophyll, before leaving to the atmosphere through stomata.

In California nursery production, light is one of the most important environmental factors influencing crop timing, plant quality, and uniformity. While the state is known for high annual solar radiation, many greenhouse operations still experience periods, especially from late fall through early spring, when natural light is not sufficient to meet the needs of certain crops. Shorter day lengths, frequent coastal fog, and prolonged cloudy periods can significantly reduce Daily Light Integral (DLI), particularly in propagation and liner production systems. 

Controlled release fertilizers (CRF) are granular fertilizers that have been coated with sulfur or a polymer. These products have been developed to allow a slow release of nutrients into the root zone throughout crop development.  In the following article we will describe several characteristics of CRFs that should be understood and various cultural practices that should be implemented to optimize nutrient use and minimize nutrient leaching when CRFs are used as part of a fertilization program.

Producing high-quality vegetable transplants requires careful fertilizer management to ensure sufficient growth and uniform plant development while minimizing input costs and nutrient losses. With rising fertilizer costs and regulatory pressure to decrease nitrogen pollution in California, efficient fertilizer usage is increasingly important. 

The California Department of Food and Agriculture confirmed the presence of Hercinothrips dimidiatus, also known as aloe thrips, in Ventura, San Diego, and Santa Barbara counties. The CDFA assigned aloe thrips a B rating, which means they determined the pest is of known economic or environmental detriment. B-rated pests can enter the state if the receiving county agrees to accept them. You can read more about B-rated pests here. 

In the Spring 2026 issue of the UCNFA Newsletter, the first Featured Article highlights the irrigation education priorities for nursery employees that were identified by focus groups of California nursery managers. In our second Featured Article, a summary of California’s floriculture and foliage industry from the USDA 2022 Census of Agriculture is presented. In Science to the Grower, researchers from Cal Poly SLO describe how monitoring fungicide effectiveness can help control powdery mildew in Brassica seedling production.

Nurseries supplying Brassica transplants face immense production challenges due to downy mildew, caused by the Oomycete pathogen Hyaloperonospora brassicae. Large-scale monoculture plantings at different growth stages, dense planting spacing, and overhead irrigation, consistently contribute to high downy mildew incidence and large quantities of downy mildew inoculum. Moreover, the cool climate and nighttime moisture of California’s Central Coast create optimal conditions for infection in outdoor nursery spaces and grower plantings.

As water scarcity and state regulations challenge California’s horticultural industry, many nurseries are turning to recycled runoff water as a primary or supplemental water source. While a “no-discharge” reality presents logistical hurdles, it also offers an opportunity to improve resource efficiency, however careful management must be taken not to spread chemical and biological contaminants throughout your property and into neighboring properties. 

Soil and Water pH

Part I – What is pH?

Part II – How is nutrient availability affected by pH

Part III – How do fertilizers affect pH?

Part IV – How to adjust pH of soils

Part V – How to adjust pH of irrigation waters

The process of adjusting irrigation water pH is the process of changing the amount of H+ or OH- ions that are dissolved in the water.  In most cases where water pH modifications are required, it is to lower pH rather than increase pH.