Climate-Ready Landscape Plant FIELD DAY

UC Davis Plant Trial Field Day 2020
Photos: UC Davis Plant Trial Field Day 2020 cr: Karrie Reid

Who should attend: Professionals from landscape, horticulture, nursery and related fields; OSU Master Gardeners; garden writers; academics/educators

When: September 14th 2022; 10am – 2pm (Arrive when convenient; ratings take about 60 min)

Where:                  OSU’s North Willamette Research & Extension Center

15210 NE Miley Rd, Aurora, OR 97002

What’s involved: Evaluating aesthetic qualities of selected landscape plants (about 60 minutes).

Photos: UC Davis Plant Trial Field Day 2020 Credit: Karrie Reid
Photos: UC Davis Plant Trial Field Day 2020 Credit: Karrie Reid

About this Event

The ever-changing climate iputs pressure on the industry to develop more sustainable plants. As part of a six-university study, OSU seeks to improve urban water-use efficiency by evaluating landscape plant performance on three irrigation treatments corresponding to the Water Use Classification of Landscape Species (WUCOLS): High, Moderate, and Low categories of water need. The plants are irrigated regularly during their first summer after planting. Treatments are imposed during the second growing season where researchers collect growth and quality ratings.

The Field Day allows landscape, nursery, and horticultural industry professionals and educators the opportunity to see new plants in their 2nd year and share your opinions and preferences by rating a representative sample of the plants in the field undergoing irrigation treatments. One plant from each of the 3 water levels, for 15 different species (some released to the public and some not yet) will be surveyed. Along with this field of 360 plants, you will be able to get a sneak peek at the next year’s field, currently in an establishment phase.

Important Details: The fields are packed dirt/uneven mulch, sturdy comfortable shoes, sunscreen and/or a hat are suggested. At the trial site, you will be provided a ratings sheet, clipboard, pen, and given general instructions when you arrive. It is a self-guided tour among our 720 landscape plants. Lots to look at but only a small sub set to evaluate. Hot Coffee and cold water will be provided. We value your feedback and hope to see you there!

For questions contact:

Brian Hill

(562) 841-1522

brian.hill@oregonstate.edu

2022 Field Day Tour and Open House

August 23, 2022

Nackley Lab nursery production open house takes place August 23. 2023 from 11am – 2pm

Our event will be a part of the great Nursery related activities happening around the Willamette Valley as part of the Oregon Association of Nurseries Farwest Show, which will also feature Dr. Nackley, and Brian Hill, M.S. and many others from Oregon State and beyond.

The Nackley lab open house will feature research on our four themes: Irrigation science, pest management, plant health, and plant trials.

Free to all, no registration required.

Parking: follow signs to south side of the Cravo North Willamette Research and Extension Center and then follow signs walk 5 mins (west) to Nackley Lab Welcome Center.


Masks are welcome, not required, per University policy

The tour route will travel through fields with uneven terrain. Farm cart transport (e.g. gators) can be available for those who request assistance.

Schedule of Events


Field Tour
11 :00 -11:15 Station 1. Welcome, overview of the program and biostimulant research on Shade-Trees
11:15 – 11:30 Station 2. Plant-based irrigation scheduling: pressure bomb and infra-red thermography
11:30 – 11:45 Station 3. ET-based irrigation scheduling and Flatheaded borer research
11:45 – 12:00 Station 4. Cover cropping and Heat-stress prevention
12:00 – 12:15 Station 5. Boxwood blight control
12:15 – 12:30 Station 6. LiDAR “smart” air-blast sprayer and drone demonstration

12:30 – 1:00 Station 1. Open chat with research team, refreshments and grilled sides.

Open House
1:00 – 2:00 Self guided tour. Researchers will be at each of the six stations to answer questions. Sprayer demos will take place at station 6 every 15 mins.

People: Oregon bound and down; From the land of sun to the land of clouds

Brent Warneke

Brent inside the west cave of Monkey Face, Smith Rock State Park.

I grew up in Littleton, Colorado amid the suburbs of Denver. Although I was a suburb kid, I grew up gardening from an early age, which sparked my love for plants. Going with what I was interested in, I decided to pursue a degree in something plant related at Colorado State University. I ended up studying horticulture, but took a wide range of classes including brewing technology, microbiology, biochemistry and business. Throughout my time at CSU I worked in a couple different lab groups, one that studied biofuel production and another that was focused on cryopreservation of vegetatively propagated crops. Working in the labs got me interested in science. I took a plant pathology course my senior year and loved how it was an integration of things I had learned in horticulture, microbiology, and other sciences.

Eventually I obtained my BS in Horticultural Science and a minor in Business Administration at CSU. I had such a good time learning about science and working in labs that I decided to pursue graduate school. I looked at a few universities throughout the USA but the prospect of working on specialty crops (fruits and nuts) had me more excited than working on field crops. I ended up landing at Oregon State University in the Botany and Plant Pathology Department. The project I worked on had me investigating fungicide resistance and grape powdery mildew management and I was fortunate to travel to many vineyards throughout the state to take samples and work with growers. Over the course of my Master’s degree I was able to present data from my research at two national plant pathology conferences, one in Tampa, FL and the other in San Antonio, TX, two places I had never been before. These experiences were very useful to hone my science communication skills which I use a lot in my current position.

Brent at Glacier Lake while backpacking in the Eagle Cap wilderness.

After I finished my MS degree I started my current position working on the Intelligent Sprayer project at OSU with Drs. Lloyd Nackley and Jay Pscheidt. The part of the project I fit into investigates using the Intelligent Sprayer to manage grape powdery mildew with various fungicide regimes and investigating sprayer coverage in hazelnut and nursery crops. This has been a great fit for me as I have been able to apply what I learned during my MS and strengthen my research and writing skills. As with all agriculture, we come up with a plan every year and have ideas about how everything will go, but something always surprises us. During the season it’s always a push to collect all the data we need, but when the season is over it is very interesting to sit down, go through the data, and make graphs and connections as to how the treatments we applied fared. Writing up the data into informative reports, and in doing so, making connections to past literature while abstracting it into the future is another part of the process that makes me love what I do.

The 50 gallon air-blast sprayer retrofitted with the Intelligent Spray System connected to a Kubota M5-111 tractor that powers the unit.

I’ve been fortunate to live in two different states that are great for my outdoor oriented lifestyle. I grew up camping, fishing, backpacking, canoeing and skiing in Colorado. I have since gotten into rock climbing, rafting and kayaking, and hunting in Oregon, and especially love spending time on the Oregon coast. If I were to give some advice to someone following a similar career path to me I would tell them to always be open to opportunities and to get out of their comfort zone regularly.

Irrigation: Drought Physiology of Ornamental Shade Trees

Sadie Keller

Highlights:

  1. Shade tree growers need to be prepared for the effects of climate change in Oregon.
  2. In order to equip growers with the tools necessary for production success, we aim to determine critical shade tree stress thresholds, characterize plant responses to drought conditions, and correlate remotely collected spectral images with ground based plant water stress measurements.
  3. Previous studies have sought drought response measurements for Acer rubrum (Red Maple) and Quercus rubra (Red Oak), but never in a nursery production setting.
  4. We aim to disseminate this information to Oregon shade tree growers at the completion of this experiment with the hope to aid growers in making data driven irrigation decisions and demonstrate the use of these technologies in nursery production settings.
Sadie in some of the shade trees equipped with soil moisture sensors and a weather station.
Sadie Keller in the shade trees equipped with soil moisture sensors and a weather station.

The Problem:

In Oregon’s Willamette Valley, the heart of the nursery country, rainfall is scarce during the summer and humidity is low. Oregon’s dry summer conditions can lead to low moisture stress conditions for maples and oaks in normal years. Plant stress resulting from low soil moisture, high heat, and low relative humidity have been exacerbated in recent years with the increasing frequency of heatwaves and drought. Drought and heat stress scorch the maple and oak canopies, which can lead to decreased plant quality and economic losses for shade tree growers. Sensor-based technologies can be used to model plant responses to environmental gradients to develop warning systems to help growers prevent stress and bridge a knowledge gap in the nursery production industry regarding drought responses.

How are we studying plant stress responses?

Starting late June 2022, we will implement two irrigation treatments (well-watered and drought) in our shade tree planting with each row having independent irrigation control. The well-watered rows will be maintained at a soil water potential of  >-1.0 mPa. The drought treatment rows will be allowed to naturally dry down to a soil water potential of -4 mPa. If during the experiment, our metrics (stomatal conductance and stem water potential) do not show considerable responses at -4 mPa tension, we will allow the drought treatment to continue to dry down progressively (-1 mPa) until stress is evident.

Why and how do we measure stem water potential?

Plant water status is commonly defined in terms of water potential or the ability of the water to do work. In most cases, well watered plants have “high” water status and drought conditions lead to a “low” water status (Levin and Nackley 2021). Using the pressure chamber, we will take midday stem water potential measurements twice weekly from 12pm-3pm. This time frame is important because it represents the time of day where leaf transpiration is at its maximum.

The pressure chamber
The pressure chamber (https://www.pmsinstrument.com/)

First, we will cover the leaf and stems to be measured with an opaque bag for at least 10 minutes before pressurization to allow the plant to stop transpiring. Once we excise the sample from the tree it should be placed into the pressure chamber or “pressure bomb” within 30 seconds (Levin 2019). Once the stem is placed into the chamber and pressure is applied, the amount of pressure that it takes to cause water to appear at the cut surface tells us how much tension the stem is experiencing.

Why and how do we measure stomatal conductance?

We measure stomatal conductance using a porometer that measures the degree of stomatal openness and the number of stomata (Licor.com). This indicates the plant’s physiological response to its current environment. If a plant is stressed, it will tend to close its stomata and lower the stomatal conductance rate. We will be using a combination of the LI-6800 Portable Photosynthesis System and the LI-600 Porometer/Fluorometer to make our measurements twice a week from 12pm-3pm.

For more information:

Please stay tuned in the coming months for more blog posts about how we will find plant stress thresholds by measuring the hydraulic conductivity of these shade trees. We will also correlate remotely collected spectral and thermal images with our ground based plant stress measurements to demonstrate how implementing a UAS equipped with a multispectral and thermal camera can be used to detect water stress in nursery production.

People: Amidst the Loblolly Pines

Clint Taylor

I grew up in a small rural town in East Texas, deep behind the piney wood curtain in a land dominated by giant loblolly pines, muddy windy rivers, and air so thick and humid it felt like you were wearing it. When was a teenager I mowed lawns and fixed up garden beds. One client I had, Miss Trixie, was getting on up in her years. She had an amazing green thumb but her age had was limiting her mobility. She would coach me through everything I did – pulling weeds, planting annuals, pruning, and fertilizing. She left me with a love of horticulture that I will carry until the end of my days.

I enriched that love by getting a BS in Horticulture at Texas A&M. While I was there I worked as a student worker for a rose and peach breeder. It was where I first learned about the land grant system and the mission of extension, and I thought at the time that is sounded like a really fun job. I also met my wife through that job. She was a horticulture student as well, and she worked on the roses and I worked on the peaches. We just never stopped hanging out, now we have been married for almost 10 years.

couple backpacking in the mountains
Clint and his wife backpacking in the mountains

After I graduated from Texas A&M I enrolled in a Masters International program at Oklahoma State University. The program merges graduate school and serving in the United States Peace Corps into one. After a little over a year of studies at OSU my wife and I were sent to Panama to serve as volunteers in an indigenous community deep in the rain forest near the Columbian border. My time in the Peace Corps was good, but also very challenging. We lived in one of the most remote sites of any of Peace Corps Volunteer in the world at that time. Illness and isolation were persistent challenges, but it was very rewarding work. We taught home gardening, and worked on clean water projects. When we left many folks in our little village of 100 people were growing their own veggies for the first time.

Clint working on a mechanical pump
Setting up an irrigation pump in Panama for clean water projects

When we returned from Panama, I took a job for a year working for Texas A&M Extension and Research doing an irrigation trial on dent corn in the high desert of Arizona. I lived and worked on a couple 1000 acre farm and learned a great deal about irrigation. A family illness brought us back to East Texas, and we became teachers. We taught high school biology and environmental science for 5 years. We used our summer breaks and holidays to build a house. Little by little we built the whole thing ourselves in cash over 4 years. After resting for 1 year we decided that we were tired of living in such a hot and humid place and decided to pack up and move “somewhere you can see mountains”. In June of 2019 I got a job working for the Small Farms Program here at NWREC and we moved to the great Pacific Northwest and never looked back.

Living and working in the Willamette valley is such rewarding experience. It is truly a horticultural paradise, with some world class soils and growers. I get do something a little different every day, sometimes installing research trials or putting together workshops for growers, and there are always  endless opportunities to hone my horticultural skills.

Pest Management: Intelligent Sprayer system automatically adjusts to seasonal growth saving thousands of dollars per year

Lloyd Nackley

Highlights

  • Airblast sprayers should be calibrated throughout the growing season to maximize application efficiency.
  • The LiDAR guided Intelligent Sprayer system automatically adjusts to crop canopy sizes.
  • Compared to standard Airblast sprayers, the Intelligent Sprayer system can reduce pesticide volumes by more than 50% while achieving adequate coverage, reducing drift by > 33%.

Our research revealed  that the majority of directed canopy spraying of specialty crops (defined here as fruits, nuts, and horticultural crops) relies on the radial air blast sprayers. There are many reasons for the continued popularity of air blast sprayers such as customizable sizes, easily available parts for repairs, and robust construction using materials such as stainless steel that provide years of low maintenance use. Although the air blast sprayer continues to be an important and effective tool for the specialty crop industry, its widespread use has not been without issues.

When radial air blast sprayers were first popularized in the 1950s, standard production practices favored hand labor, tree varieties popular at the time were around 6 m tall at maturity, and vines had large dense canopies. Modern plant breeding and horticultural practices, such as pruning and training systems, have revolutionized specialty crop production leading to higher density production systems designed for mechanization. Modern horticulture favors smaller trees (1–4 m tall) that are more productive per unit area than their historical counterparts, and pruning and trellis systems that create more open canopies. Despite the physical transformation of specialty crop production systems, the design of radial air blast sprayers has stayed largely the same. Consequently, unmodified radial air blast sprayers emit air and pesticide volumes that are often much greater than needed in modern high-density, open canopy systems.

Air blast sprayers from their early years to current day. (A) ‘Speed Sprayer’ on the Brown Fruit Farm near Worthington, OH, USA, 1947 (image courtesy of worthingtonmemory.org). (B) Air blast sprayer being used in research trials at the Ohio Agricultural Research and Development Center, Wooster, OH, USA, 1966. (C) Air blast sprayer at Rears Manufacturing in Coburg, OR, USA, 2018 From our publication.

Optimizing spray applications is necessary to address increasing pesticide expenses, limited labor availability, stricter regulations, and increased public awareness of pesticide use. For four years the Nackley Lab and Dr. Jay Pscheidt at OSU  have been collaborating with USDA-ARS, and the Fulcher group at the University of Tennessee to investigate application of a sensor-guided sprayer in horticultural systems. Sensor-based systems can apply a variable-rate spray that adapts to the changing canopy volume and density thereby reducing waste and off-target deposition compared with standard constant-rate sprayers.

Water sensitive spray cards are used to measure the coverage from applications by standard and sensor-based Airblast sprayers.

We tested the effect of variable- and constant-rate spray applications and phenological stage on spray volume, coverage, and deposit density in two perennial specialty crop systems: an apple orchard and a grape vineyard. Our research showed that the greatest differences in the volume of pesticide application between constant- and variable-rate sprayer modes occurred early in the season when the canopy was sparse. The standard spray mode discharged a constant volume regardless of the canopy characteristics causing pesticide spray to drift through the open canopies beyond the desired target. Reducing nontarget deposition is critical because aerial drift, ground spray, and runoff can contaminate surface and groundwater and have toxic effects on nontarget species. Unlike the standard spray mode, the Intelligent sprayer mode made real-time adjustments, decreasing the application volume when vegetation was absent, which resulted in a more targeted spray and decreased drift and off-target ground spray. Increasing spray efficiency is critically important because spray losses to the ground and aerial drift by constant-rate, air-assist sprayers can be 40% to 60% of total applied spray in orchards and 10% to 50% the total applied spray volume in vineyards.

Intelligent sprayer system in a red maple nursery.  https://agsci.oregonstate.edu/nursery/precision-spray-applications

If disease and arthropod control are not diminished, reducing the pesticide volume applied on a farm has multifaceted benefits. The most direct benefit, and usually the one that motivates the adoption of variable-rate systems, comes from a reduction in pesticide costs due to lower application volumes. Other research found variable-rate technology can reduce pesticide costs by as much as 67%. Reducing the amount of active ingredient per application also causes a concomitant decrease in environmental impact and worker exposure. Moreover, when the quantity of pesticide required to treat an area is decreased, additional efficiencies are realized from the reduced need to refill, such as lower fuel and labor costs, and improved ability to complete applications in windows of good weather. Additionally, requiring less water as in the case of lower spray volumes is beneficial for orchards and vineyards that have limited access to water.

More info:

Warneke, B.W., J. Pscheidt, and L.L. Nackley. 2021. How to do regular maintenance on air blast sprayers to ensure proper care for specialty crops. https://catalog.extension.oregonstate.edu/em9316

Warneke, B.W., J Pscheidt, R. Rosetta, and L.L. Nackley. 2019. Sensor Sprayers for Specialty Crop Production https://catalog.extension.oregonstate.edu/pnw727

Nackley L.L., B.W. Warneke, L. Fessler, J. Pscheidt, D. Lockwood, W.C. Wright, X Sun, and A. Fulcher. 2021. Variable-rate spray technology optimizes pesticide application by adjusting for seasonal shifts in deciduous perennial crops. HortTechnology 31 https://doi.org/10.21273/HORTTECH04794-21

Warneke,B.W., H. Zhu, J. Pscheidt, and L.L. Nackley. 2020 Canopy spray application technology in specialty crops: a slowly evolving landscape. Pest Manag Sci 77: 2157–2164

Irrigation: Tip the scales to efficient irrigation with mini-lysimeters

Dalyn McCauley

Highlights

  1. Nurseries grow a wide variety of species and use many different crop production methods which can make effectively scheduling irrigation difficult.
  2. Mini-lysimeters are devices that measure evapotranspiration (ET) via a change in weight of a containerized crop.
  3. Mini-lysimeter controlled irrigation has shown to reduce water use and conserve nutrients while producing plants of marketable size and quality.

The need for sensor-controlled irrigation

Irrigation scheduling for nursery is complex due to the wide variety of species grown, the variety of pot sizes, the differences in growing media, and differences in environmental conditions (i.e. greenhouses, hoop-houses, field nurseries, or use of shade cloths). These factors all influence the specific crop water requirements, making it difficult to determine a generalized irrigation solution. As such, irrigation scheduling is commonly based on grower intuition and experience. For example, it is common for an experienced grower to pick up pots as they walk through a can-yard to get a feel for the weight and irrigation need. With funding support from the ODA-OAN research program, we sought out to develop an automated sensor-controlled irrigation system that is based off container weight, referred to as a mini-lysimeter controlled irrigation system.

What are lysimeters?

Lysimeters are devices that directly measure crop evapotranspiration (ET), which is the transfer of water from the soil to the atmosphere through plants by transpiration, and from the soil by evaporation. Lysimeters consist of a tank filled with soil and crop that is placed on a scale. Any change in weight of the tank is a direct measure of water moving in or out of the system. This provides a direct measurement of water consumption from the tank’s boundary, which can be used to inform irrigation scheduling. Lysimeters have historically been used in agronomic crops like wheat, alfalfa, or legumes. However, they can be scaled down for use in nursery and greenhouse crops, which are often referred to as mini-lysimeters (Fig. 1). You can read more about mini-lysimeters and their many applications in our recent publication

a mini-lysimeter being used for irrigation of hemp
An example of a mini-lysimeter being used to control irrigation of hemp at NWREC

System Design The mini-lysimeter controlled irrigation system at the NWREC consists of 16 mini-lysimeters. They are suitable for measuring up to 10kg (22 lbs.), which can accommodate up to a 3-gal container (Fig. 2). The mini-lysimeters are hooked up to a Campbell Scientific CR1000X data logger (Campbell Scientific Inc, Logan, UT) using a multiplexer. The system is programmed to trigger irrigation for a zone based on the average container weight. This ensures that the applied irrigation is representative of the variability between containers, such as differences in the water holding capacity of the media, and irrigation uniformity. A guide detailing the design, calibration, and performance of the mini-lysimeter controlled irrigation system and can be found here.

An exploded view of the mini-lysimeter assembly.
An exploded view of the mini-lysimeter assembly. The device has a footprint of 10 x 10 x 2in.

System Performance When mini-lysimeter controlled irrigation is compared to traditional irrigation methods (i.e. irrigation on a timer), it has shown to use less water while producing plants of equal size and quality. Read more about this study here. Mini-lysimeter-controlled irrigation also responds more effectively to the seasonal and daily variations in water demand, increasing irrigation frequency during hot and dry conditions, and foregoing irrigation during cooler days or after rain. This is particularly salient as extreme weather events become more frequent. Having another set of eyes (sensors) looking over your crops can help reduce losses from over- and under-watering.

People: A Career Path as the Crow – Or the Raven – Flies

Raven Hartley

I spent my childhood in western New York where my mom took us hiking, mushroom foraging, and taught us how to identify the deciduous trees around us. We moved to Oregon when I was 10 and not much has changed except the forests were now coniferous and we learned to brave the rain. My love of plants and ecology was sparked during these weekend trips as I learned how all organisms are interconnected.

Raven taking leaf measurement with a Licor-600 at NWREC.
Raven taking leaf measurement with a Licor-600 at NWREC.  

When I started my undergraduate degree, I had no idea what I wanted to do and jumped from major to major. After 2 years at community college, I transferred to Oregon State University and landed on marine biology. During this time, I had the opportunity to be a research assistant in Utila, Honduras for Operation Wallacea and lead scientific dives for PhD student Nadia Jogee. Through this experience I realized my love of problem solving that goes along with field research, but despite my enjoyment I felt that marine biology wasn’t quite what I wanted for a career.

Once the pandemic hit and I was suddenly home all the time, I started to collect house and landscape plants to improve my living space. I had a lot of fun learning to care for them and read up on nutrient needs, soil types, watering, pruning, and propagation. A lot of this information I found in extension articles that led me to the College of Agricultural Science at OSU. I now have research experiments that focus on improving plant care and management practices in nursery production systems.

I’m now in the last term of my undergraduate degree in Horticulture and am fortunate to have been in the accelerated master’s platform (AMP) for the last year, with Dr. Lloyd Nackley and Dr. Ryan Contreras as co-advisors. This program has allowed me to get a head start on my graduate coursework and field research with the support of my advisors and other faculty. I have gotten to learn so much in the last year from propagating cuttings, to finishing plants, best management practices, and so much more. I also get valuable lab experience working for Dr. Carolyn Scagel at the USDA-ARS Horticulture Crops Research Lab where I have assisted with tissue collection, water sampling and nutrient and data analysis to aid in her plant physiology research. My favorite part of research is getting to work outside to conduct experiments and getting to work alongside so many great and knowledgeable people!

An overhead view of Raven’s project on container grown oak trees at the North Willamette Research and Extension Center (NWREC).
An overhead view of Raven’s project on container grown oak trees at the North Willamette Research and Extension Center (NWREC).

Plant Health: When Do Shade Trees Do What They Do?

Brian Hill

A Phenology Study is underway at NWREC!

The pretty flowers of spring, shade providing leaves of summer, and fire like colors of fall help us know when the seasons are changing. We use calendars to plan everything in our lives. Nature does the same but not in the same way.

Progression of seasonal changes in shade tree crown and color
Shade tree seasonal progression from spring (top left) to fall (bottom right).

What causes trees to change?

We can all remember early spring weather that was warm and dry as well as those years when we hoped our 4th of July BBQ would not get rained out. These weather differences from year to year influence events in nature that are crucial for species to survive. Plants and insects go dormant over the cold winter and begin growing in the spring and do it without a single calendar. They use day length and temperature to schedule their life events. The day length in the Willamette valley changes from 8 hours and 46 minutes in winter to 15 hours and 36 minutes in summer. These changes are predictable because they are cause by the tilt of the Earth, which doesn’t change. Our calendars align with these dates (winter solstice and summer solstice).Temperature, however, is unpredictable because there are a vast number of factors that influence it.

What changes are we monitoring?

A large part of the nursery industry in Oregon is dedicated to growing shade trees. Best management practices require monitoring for signs of event changes throughout the tree’s life cycle. This is known as Phenology, defined as the study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life. The Nackley Lab has a small in ground tree nursery that we use for experiments. For the past 3 years we have been conducting a Phenology Study where we have tracked the dates our tree events happened.

Monitored events in our Phenology study

  1. Bud Break: Date when the protective scale coating is shed from the bud exposing the tender new growth shoot
  2. First leaf: Date the first leaves are completely unfolded on at least 3 branches
  3. All Leaves Unfolded: Date when 90% of buds have reached first leaf
  4. First Flower: Date the first flowers are opened and stamens are visible on at least 3 branches.
  5. Full Flower: Date when half or more of the flowers are fully open
  6. First Ripe Fruit: date when the first fruits become fully ripe or seeds drop naturally
  7. Full Fruiting: Date when half or more branches have fully ripe fruit or have dropped seeds
  8. 50% Color: Date when half or more of the branches have leaves that have started to change color
  9. 50% Leaf Fall: Date when half or more of the leaves have fallen off the tree
image shows the phenology stages of flowering trees
Phenological stages of flowering trees from bud break (top left) to full flower (bottom right).

How can this information be useful?

As we collect data in year 3 (2022) of this study we are excited for how this data may be used in the future. Temperature data can be used to make degree day models which are based on heat units. The number of heat units per day are added together in a running total. This information is much better at predicting events in nature when compared to calendars. When growing shade trees in a production nursery setting, defending the crop from disease and predators is essential. Spraying a tree with a fungicide at bud break keeps them growing healthy. Spraying pesticides at first flower protects trees from insect attacks. By creating degree day models, growers can predict when to apply chemical protection for trees, eliminating double applications caused by calendar reliance.

Growers know the uncertainty caused by a changing climate impacts tree growth events. It’s hard not to trust the calendar dates which we plan everything else in our lives by. Future projects include modeling the events recorded over the last 3 years, and seeing how they align with degree day accumulation. The end goal is to use what we’ve learned to help keep the labor and pesticide costs down for the local nurseries while the produce the beautiful tree’s we all depend on.

People: California Grown Grad Student Studies Plant Physiology Drought Responses

Sadie Keller

My path to pursuing a Master of Science in Horticulture has not been straight and narrow. Ironically, growing up in California’s Central Valley, I wasn’t aware of the career possibilities in agriculture and horticulture. I’d always possessed an affinity for plants and the outdoors for as long as I can remember. My earliest memories involve working in our backyard garden with my dad and raising chickens.

I graduated high school with a love of science and headed to college to pursue an engineering degree. After two years of struggling with my major, it was time to come home and assess my options. I started attending classes at a local community college and found a job working farmers markets on the weekends. Little did I know, this experience would change the rest of my life. I loved this job and it showed me what I was passionate about; the environment, sustainability, irrigation efficiency, and building climate resilient landscapes and agriculture systems.

Keller measures stem water potential using pressure bomb method
Sadie measures stem water potential using a pressure bomb.

I transferred to California State University, Stanislaus to obtain a Bachelor of Science in Agriculture. From this point on, I have thrown myself into every possible internship and work experience to expand my skills and deepen my knowledge. I’ve worked as a nursery technician, a field scout, a CSA assistant, a standards program aide for the county, a trapper, an inspector, and research assistant. In February of 2020, I was selected to attend the Future Leaders in Agriculture Program in Washington D.C. with 20 other students from around the U.S. where my eyes were opened to the vast opportunities available in agriculture.

Now, as a Graduate Research Assistant in the Nackley Lab, I study ornamental plant vascular systems responses to drought conditions and stem hydraulics. Being at Oregon State and a member of the Nackley Lab, I feel like I am getting the most hands-on experience and interdisciplinary education possible. I am getting lab experience working for Dr. Carolyn Scagel at the USDA-ARS Horticulture Crops Research Lab where I support her plant physiology research by helping with tissue and water sample collection, processing, and laboratory analyses related to plant water relations and plant mineral nutrition. With Dr. Nackley, I am getting to explore my interests in remote sensing technologies and learning how I can incorporate these technologies into my thesis project. I am also a TA for his Plant Nursery Systems class this Spring. My favorite part about doing research is working at NWREC over the summer with our lab team and other graduate students.

computers and equipment used for plant physiology studies
Sadie’s work settings, her home away from home.