January 2025
Trade Journal Articles
Spray Stakes for Nursery Production: Pressure compensating emitters increase distribution uniformity of spray-stakes but may be cost prohibitive for nursery production
By: Gerry Spinelli & Chris Shrogren / NurseryMag Dec 2024
Friends of the lab at UCANR-SCREC Gerry Spinelli & Chris Shrogren recently shared some of the work they have been doing on irrigation distribution uniformity. Spray stake technology has been widely used in nursery production, but its distribution uniformity has not been well studied. Recent innovations, such as pressure-compensating (PC) emitters, improve water distribution but can be costly. Tests showed that PC emitters achieved higher uniformity (0.95) compared to non-PC models (0.82-0.85). However, the investment in PC emitters would take 4-6 years to break even based on water savings in Southern California. While PC emitters enhance efficiency, their high cost may hinder adoption in commercial operations.
It’s Getting Hot In Here! The temperature of your growing media affects root growth and fertilizer release rate
By: James “Jim” S Owen Jr, & Jake Shreckhise / NurseryMag Jan 2025
Friends of the Lab, at USDA-ARS, who we’re working with in a national level project to understand heat in nursery containers recently shared some work about how as summer temperatures rise, container-grown plants face serious heat stress, with root zone temperatures soaring above ambient air levels. Black plastic containers can reach 130°F, causing root damage and reduced growth. Key temperature thresholds to monitor include:
- 50°F: Fertilizer release begins
- 75°F: Continuous nutrient release
- 85°F: Growth stunting risk
- 100°F: Root damage begins
- 115°F: Cell death within 30 minutes
As they also shared in a recent Digger article, growers can mitigate heat by using light-colored containers, adjusting irrigation schedules, and monitoring media temperature with sensors to ensure optimal plant health and growth.
Growing Knowledge: Focusing on silicon
By: Jana Lee / Digger Jan 2025
Friends of the blog and researchers at USDA ARS & OSU in Corvallis studied the effects of silicon-calcium supplementation on rhododendrons to reduce lace bug infestations. Silicon can strengthen plant tissues, making them tougher for insects to feed on, and may also alter plant chemistry to reduce digestibility. The study found that silicon applications reduced feeding damage and egg-laying by 25-75%. However, it did not significantly increase silicon accumulation in plant leaves. While promising, further research is needed to determine long-term benefits for pest control and overall plant health in landscape settings.
Scientific Journal Articles
Effects of Reduced Substrate Volumetric Water Contents on the Morphology and Physiology of Three Landscape Shrubs Grown in a Greenhouse
By: Ji-Jhong Chen and Youping Sun / HortScience Vol 60: Issue 2
Friends of the Lab, JJ Chen (U-WY) and Youping Sun (USU) shared some more results from their Climate Ready Landscape Plant Project, With rising temperatures and less rainfall, cities are pushing for drought-tolerant landscaping. A study tested Petite Knock Out® rose, ‘Arp’ rosemary, and Blue Diddley® chaste tree (Vitex) under reduced water conditions.
🌿 Roses struggled the most, with major growth reduction and heat stress.
🌱 Rosemary looked better but was still heat-sensitive.
🌳 Chaste tree (Vitex) handled drought best, staying cooler with minimal growth loss.
These results suggest that for folks focused on water-wise landscaping in the intermountain West, chaste tree and rosemary are better picks than roses. Choosing drought-tolerant plants keeps landscapes thriving while conserving water! 💧🌿
Two Cold-Hardy Chinese Woody Plants For Consideration by Oregon Growers
By: Jia-le Peng, En Wu, Da-mao Zhang, Ling Li, Yi-wen Wu, Xiaoying Yu, Don-lin Zhang, and Yan-lin Li & Minghan Luo, Sijun Qin, Deguo Lyu, and Jiali He
HortScience Vol 60: Issue 2
Two new cold-hardy shrubs, ‘Xiangnong Xiangyun’ Loropetalum pronouced “Shang-nong Shang-yoon” and ‘Hongzi Die’ Crabapple, offer unique ornamental value and strong adaptability, making them ideal for Oregon growers.
‘Xiangnong Xiangyun’ features creamy yellow flowers, compact growth, and excellent cold tolerance. It thrives in open-field conditions with minimal pruning and high pest resistance, making it a low-maintenance option for landscapes. Propagation is simple, with cuttings achieving a 90% survival rate, while cleft grafting and budding ensure strong, stable plants.
‘Hongzi Die’ Crabapple boasts semi-double, dark red-purple flowers, glossy foliage, and abundant red fruit. Hardy to -25°C, it thrives in full sun and well-drained soils, with a high survival rate using bud grafting. Its disease resistance and adaptability make it an excellent choice for cold regions.
Both varieties provide vibrant color, seasonal interest, and resilience, expanding options for nurseries and landscapers in cooler climates. 🌿❄️
Do Hybrid Butterfly Bushes Have Less Seed Production? What This Means for Oregon’s Invasive Plant Rules
Cara Still and Ryan Contreras / Journal of Environmental Horticulture Vol 42 Issue 4
Friends of the Lab, here at Oregon State University, looked at Buddleja davidii, a popular ornamental plant, which is classified as a Class B noxious weed in Oregon. However, there is no clear evidence that interspecific hybrids consistently show reduced seed production, which would lower their invasive potential. This study examined the seed production of 34 Buddleja cultivars, including hybrids, across field, greenhouse, and open-pollinated populations. The results showed no consistent correlation between hybridization and lowered seed production, with some hybrids exhibiting both high and low seed production. Flow cytometry analysis revealed minimal variation in genome size. The study underscores the importance of testing all cultivars of invasive species, regardless of hybrid status, to guide regulations and protect ecosystems without negatively impacting the nursery industry.
Boxwood Production Costs and Strategies for Nursery Growers
By Charles Hall / Journal of Environmental Horticulture Vol 42 Issue 4
Nursery industry’s favorite prognosticator, Charlie Hall, has emphasized that understanding the economics of nursery production is critical for growers. This study modeled three common production scenarios for boxwood (Buxus L. spp., Buxaceae) in #3 containers [11 L (3 gal)] in the U.S., and is particularly relevant to Oregon growers due to the high value of boxwood production in the state, which generates millions of dollars annually. The analysis, based on best management practices and grower interviews, examined material inputs, equipment use, and labor. The results showed variable costs ranging from $8.98 to $11.26 per plant depending on the production scenario. Labor made up the largest share of costs, followed by materials like containers, transplants, irrigation, and fertilizers. Boxwood remains a key plant in the green industry, and the findings provide valuable insights for nursery growers and policymakers, especially as boxwood blight continues to pose a threat.
