Tag Archives: horticulture

IPM

IPM: Early Season Scouting – Where to look when there’s nowhere to look (yet!)

Leave a comment

Melissa Scherr

Scouting for insects and areas of potential introduction early in the spring can save headaches long into the season, and it’s relatively simple with just a few inexpensive pieces of equipment. The basic starter toolkit includes just a hand lens or magnifying glass, a sheet of white paper on a clipboard, and some flagging tape to easily mark trouble spots. Easy enough, you say… but what are we looking for with these tools?

hand lens held in hand
A standard hand lens, equipped with a small light
worker wearing head lens examining plant
Head gear equipped with magnification can aid in searching plants for small insects

In General

Beginning early in the season and identifying where problems are most likely to emerge first will allow targeting in regular scouting and monitoring activities. Using online tools like Degree Day models for your county can also help identify when the pests are likely to move into crops based on this year’s weather data, especially when combined with information from previous years’ scouting records.

Where to Sample

When initiating scouting activities, it’s also important to consider the entire landscape of the operation. Though monitoring hotspots and suspected problem areas will help with anticipated infestations, creating sections of manageable scouting areas throughout the operation will help avoid unanticipated outbreaks as well. It’s tempting to stick to the “most affected” areas, but that limits the ability to see the whole picture. Make sure to also examine common entry ways for workers and machinery as these can act as vectors of pests.

Dividing space into equal sections and sub-sampling can save time while making sure all areas within a crop are sampled

For nurseries and greenhouse where plants are in pots for most of the season, it’s important to search not just young plants, but the media and the pots themselves. The media, if not sanitized, should be inspected for overwintering grubs, mites, and other small pests that enjoy cool, wet substrate, like springtails. In pots with plants, search the bottom of the stems where they come into contact with the soil, lightly scraping to disturb any inhabitants and observing activity. For plants that have overwintered in pots, select several representative pots to remove soil up to 12” from the stems to search for grubs like cutworms.

rows of pots with plants
Make sure to search not only the plants and soil, but the edges of the pots as well.

Pots that have overwintered plants or substrate should be checked thoroughly, inspecting under the rims of the pot (for those with a folded over lip), under the pots, and upon removal of the plant and soil if possible, inside the pot. If the entire plant, roots and soil can be gently removed to examine the inside of the pot, also check the roots and substrate for evidence of tunneling around the pot.

What to Sample

Sampling for insects isn’t like any other organisms because insects are small yet highly mobile, yet in their relatively small range can be highly exploitative. For this reason, be prepared to look for more than just insects, but also their products and proof of activities.

Look for:

  • Stressed plants: otherwise healthy-looking plants with branches that appear wilted or weakened; whole plants that appear sick while others are not affected. Search the leaves, stems and plant crevices for evidence of insect presence
wilted plant
Stressed plants are a good indicator of pest presence, especially when stress is limited to one or a few plants initially.
  • Honeydew: sticky sap covering leaves or stems, appearing to have dripped from other surfaces as a result of sap-feeding insect activity on the plant – this sap may also be growing molds or other fungus secondarily
sap on plant leaves
Sap leaked onto surface of leaves from insects feeding above
  • Frass: insect poop. When insects tunnel and feed, they leave behind frass in the form of sawdust-like piles, black or brown flecks, or poop stuck to fine silken webbing in the case of silk-producing insects.
insect poop on leaf
Insect frass is often the same color as the food source, or black flecks
  • Exuviae: the shed skins of insects, lost as the insects grow. Usually seen later in the season, but as some insects emerge from their overwintering stage, they may molt and leave their exuviae on the surface of the soil, on their host plant, or on nearby artificial structures (especially in greenhouses).
leafhopper and shed skin
The shed skin often resembles the insect and can be used to identify the pest

How to Sample in Early Spring

1. Beat Sheet/Tap Sample

A beat sheet is a large square sheet held under foliage while the foliage is vigorously shaken or beaten with a stick. As one can imagine, this is less reasonable for tender young nursery and greenhouse plants. However, it can be easily modified for more effective and less damaging use when scaled down to a plain white sheet of paper on a clipboard as suggested in the aforementioned toolkit. Holding the clipboard under the plant, gently tap the plant with your finger to dislodge any insects that may be attached to the plant – usually anywhere from 30-60 seconds is plenty. Using the hand lens, the insects can then be identified and counted.

using a ruler to tap over a paper
Using a ruler or pencil can create a more consistent sample

2. Aspirator

These are readily available on supply websites, and can be used to gently vacuum small insects off of plants and sheets of paper for identification with a microscope, for freezing/preservation, or simply to remove the pest from the plant.

an aspirator is used to sample insects on lavender
Scouting for insects with an aspirator

3. Berlese Funnel

If activity is observed in plant substrates, this is helpful in identifying the specific insects and arthropods present. A sample of the media is introduced into the funnel with a light/heat source above. As the sample dries and heats, the insects move deeper into the funnel, eventually falling through to the collection cup for easier preservation and identification. A soda bottle and desk lamp are sufficient for a makeshift Berlese funnel.

berlese funnels
Large berlese funnels for large soil samples
desktop lamp and soda bottle works as a makeshift berlese funnel
A desktop lamp and soda bottle works as a makeshift berlese funnel

4. Sticky Cards

A traditional means of monitoring flying pests, use appropriate density according to location (In general, 1 card per 1,000 ft2 is standard). There are a few different types to monitor specific pests: blue cards attract mainly thrips; yellow cards attract multiple species. If you have crawling pests, you can place them on the bench overnight (when crawling insects tend to be the most active. To collect, simple cover with a piece of plastic wrap and observe insects using hand lens or magnifying glass. Things to remember: aphids have a life stage that is wingless, and thus won’t be caught on sticky cards; if natural enemies are released, REMOVE sticky cards as they will also capture these beneficial insects.

blue and yellow sticky cards
Yellow and blue standard sticky cards
yellow sticky card with insects
Sticky cards capture small flying insects when suspended in plant canopies

5. Potato Trap

In western Oregon where there has been a good deal of rainfall through the winter, monitoring fungus gnats is especially pressing in the early spring. Potato slices placed onto the surface of the soil/substrate is an excellent trap for fungus gnat larvae, both to monitor populations and to remove them from the soil.

6. Trap Crops

As it becomes time for pests to invade crops, early placement of trap crops and distract them from cash crops. They can also provide services as sentinel plants to warn of increasing pest populations as the season continues, as well as track phenology. Well known trap plants are:

  • Tomato, eggplant, lantana or marigold for greenhouse whitefly
  • Marigolds, crotons, chrysanthemums, roses, impatiens and ivy geraniums for spider mites.
  • Peppers and fuchsias for aphids.
  • Gerbera, verbena or chrysanthemum for thrips 

Remember

Scouting for insects changes with the season, but there are things that can be done early in the year to discourage and stay on top of changing conditions. Good record keeping and persistent monitoring are the keys to success when it comes to keeping pests at bay!

Nursery Knowledge

Nursery Knowledge: Plant Hydraulic Physiology – Unlocking Nature’s Water Secrets for Greener Futures

Leave a comment

Lloyd Nackley

TL;DR: Plant hydraulics unravels the journey of water within plants, aiding tree health, nursery production, urban forest management, and climate resilience. 🌿🌍

In 2023, we delved into the fascinating world of xylem architecture and how plants move water. In this post, we’ll uncover the secrets of how trees and other woody plants manage water, adapt to challenging conditions, and ultimately contribute to a greener, more sustainable world.

sprinklers watering young trees
Overhead watering in red maple saplings

Real-Life Examples

Understanding plant hydraulic physiology has real-life applications that impact our daily lives. Think about the forests that surround your town or city. These vast woodlands provide us with habitat for wildlife, clean air to breathe and recreational spaces. Knowing how water moves through trees helps us manage and protect these valuable resources. For example, foresters use this knowledge to assess the health of forests and make decisions about when and where to plant new trees. . Additionally, farmers use plant hydraulic physiology in agriculture to develop more resilient crop varieties that can withstand droughts, ensuring a stable food supply. So, the next time you hike in the woods or enjoy a fresh piece of fruit, you’ll know that plant hydraulic physiology plays a crucial role in making it all possible.

Plants water-saving superpowers

Imagine it like this: when the soil dries and the plant begins to get thirsty, it doesn’t just rely on its stem. It has other ways to stay healthy. Think of these ways as a set of superpowers. These superpowers help the plant survive when the soil water is unavailable.

plants in dry soil
Native and naturalized plants are better at managing body water in response to their environment

One of these superpowers is stomatal conductance. It’s like the plant’s ability to open or close tiny valves on its leaves to save water. When water is scarce, it can close these valves to keep as much water as possible. Another superpower is leaf conductivity. This is about how well water moves through the leaves. The plant can control this too. When it’s thirsty, it can slow down the flow of water through its leaves. And then, there’s leaf wilting, which you might have seen before. When a plant wilts, it’s like it’s saying, “I’m really thirsty!” It’s a sign that the plant needs water.

These superpowers don’t all kick in at the same time. First, the plant might adjust its stomatal conductance andits leaf conductivity, before things get serious, and stem conductivity is affected. Scientists have studied these superpowers in different plants. Some scientists have proposed the theory of a plant hydraulic fuse, much like a fuse on a stick of dynamite. The idea behind the plant hydraulic fuse is that plants have a mechanism to prevent catastrophic failure in their water transport system. When faced with extreme water stress, they can cavitate (or burst) segments further from the main stem. Blowing-off the edges to preserve the main trunk. This deliberate disruption helps protect the most vital parts of the plant from experiencing embolisms (blockages) and ensures its survival. They’ve figured out the order in which these superpowers come into action when a plant is thirsty. This information helps us understand how plants deal with water stress.

planted ornamental plants in landscape
Studies help to understand what plant attributes allow for better success in drought conditions

Nursery production and practical applications

For nursery professionals, knowing about these superpowers can be helpful. It’s like having a manual for taking care of plants. By watching for signs of plant water stress, like wilting leaves, or measuring stem conductance, leaf transpiration, and plant water potential, professionals can decide when to water the plants to keep them healthy. In the world of nursery production, where we grow young plants to get them ready for life outside, understanding plant hydraulic physiology can be a real game-changer.

Let’s break it down:

Watering Wisely: Imagine you’re caring for a garden, and you need to water the plants. You could just eyeball it and water them when they look thirsty (like when they start to wilt). But, there’s a smarter way. You can weigh the pots to figure out when they need water based on their weight. It’s like checking the gas tank in your car to know when it’s time for a refill. Even smarter, you can use science to measure how much water the plants need based on how they’re doing on the inside. This way, you don’t have to wait until they’re wilting to know they need water. It’s like having a fitness tracker for your plants!

plants irrigated in a greenhouse
Managing water in a greenhouse is a function of understanding plant physiology while remaining economical

Getting Tough: Plants are like little superheroes. They can learn to handle tough situations, like not having enough water. Just like how training can make athletes stronger, exposing plants to a bit of stress (like less water) in the nursery can help them be more resilient when they’re planted outside.

Finding the Balance: Sometimes, you have to make tough choices when growing plants. If you water them too much, they might get sick. But if you don’t water them enough, they won’t grow well. It’s like finding the right balance between playing in the rain and staying dry.

Environmental impact

Plant hydraulic physiology isn’t just about plants; it’s about our planet’s health too. As we face environmental challenges like climate change, understanding how plants manage water becomes increasingly important. Imagine a world where plants couldn’t adapt to changing water conditions. It could mean more forest fires, reduced crop yields, and even less greenery in our cities. By studying how plants cope with water stress, scientists and conservationists can make informed decisions about preserving ecosystems and mitigating the effects of climate change. This knowledge also guides water-saving practices in agriculture and urban planning, helping us use this precious resource more efficiently and sustainably. So, when we learn about plant hydraulic physiology, we’re not just exploring the inner workings of plants; we’re taking a step towards a healthier planet for everyone.

So, what’s the bottom line? Knowing how water moves in plants can help nursery professionals make smart decisions. It’s like having a playbook for growing strong and healthy plants. And by using science, we can grow better plants while saving water and protecting the environment. It’s a win-win for everyone!

Meet The Team, Nursery Knowledge, Plant Health

Plant Health: Drones and Drought

Leave a comment

Lloyd Nackley

Roots, Shoots, and Sky-High Science and Extension: Our dedicated team has actively engaged in research and extension events this year that offer valuable insights into plant ecology and climate change adaptation.

Field Research: Graduate student Scout Dahms-May led extensive research into how ornamental shrubs respond to drought conditions. Her dedication shone through as she ventured into the field for pre-dawn plant water potential assessments, sharing the experience with hot air balloonists and the local coyotes. Our excellent undergraduate students, along with the new graduate student, Josh Perrault, played a pivotal role in the research by meticulously measuring the leaf area of over 100 plants. Their hard work serves as a testament to the commitment of students pursuing cutting-edge agricultural research.

Extension: Standout events this season included an impressive demonstration of sprayer drones. Visitors had the opportunity to witness these cutting-edge technologies in action, gaining insights into how they can be used in modern agriculture and horticulture.

Another highlight was a grand field day that showcased the spirit of collaboration at NWREC, involving students, staff like Brent Warneke, Dalyn McCauley, and Clint Taylor from the Nackley Lab, as well as guest appearances by experts, including Dr. Rebelo, a visiting scholar from South Africa, and Dr. Wiman, Orchards Program Leader, and Dr. Yang, a Blueberry Extension Specialist. This summer, NWREC demonstrated its position as a hub of research, learning, and community engagement, driven by our shared commitment to advancing the field of plant science.

Irrigation, Nursery Knowledge, Plant Health

Nursery Knowledge: Plant Hydraulic Physiology

Leave a comment

Lloyd Nackley

Unlocking Nature’s Water Secrets for Greener Futures, Part 1

TL;DR Plant hydraulics unravels the journey of water within plants, aiding tree health, nursery production, urban forest management, and climate resilience. 🌿🌿

Last month, we delved into the fascinating world of soil hydraulics, exploring how water moves beneath our feet. In this post, we’re staying within the realm of water movement but shifting our focus to a different dimension of nature – plants. Prepare to journey through the intricate pathways of plant hydraulic physiology, where we uncover the secrets of how trees and other woody plants manage water, adapt to challenging conditions, and ultimately contribute to a greener, more sustainable
world.


Plant hydraulic physiology is all about how water moves through plants. Scientists study this to understand how trees and other woody plants react when they have enough water or not enough. This knowledge helps us figure out how different ways of growing plants in nurseries affects their growth. People have known for a while that this field is important for plants in forests. But now, thanks to recent discoveries by this lab and others, this amazing field of science is being applied to
nurseries and other horticultural production systems. In this summary, I will explain the basic ideas about how water moves through
plants , how it connects to their structure and how they work. With this knowledge, scientists, nursery workers, and people who care for forests can ensure they grow strong, healthy trees that can handle harsh conditions when planted outside.

UNDERSTANDING WATER MOVEMENT IN PLANTS
Let’s start by talking about how water moves in plants. Imagine it’s like water moving through a hose in your garden. We can measure this flow of water using something called “flow rate,” which is just how much water moves in a certain amount of time.

We use units like gallons per minute or liters per minute to measure it. For example, think about a water hose in your garden. If you want to know how much water it sprays out in a minute, that’s its flow rate. Now, here’s something interesting: the size of the pipe or hose matters. A big hose can let a lot more water flow through than a tiny one. In fact if you double the diameter of a hose it can allow 4 times the flow of the smaller diameter hose. Plants have tiny water pipes called “xylem.”

XYLEM CONDUCTANCE
Okay, now let’s talk about “conductance.” Think of it as how easy or hard it is for water to move through something. For plants, this refers to how easily water can travel through their pipes. We usually keep the pressure the same, like when you use a hose with a constant water pressure. This helps make sure the plants get water evenly. Lastly, there’s something called “conductivity.” It’s like a fancy version of conductance but scaled to the size of different parts of the plant. It helps us compare how different parts of the plant move water. For example, we might want to know how water moves through the stem compared to the roots.

Now, here’s where it gets cool: in plants, water doesn’t get pushed like in your garden hose. It gets pulled up by something called “tension.” This happens because plants lose water from their leaves when it evaporates. Imagine a plant sipping water through a straw from the soil. When the water evaporates from the leaves, it creates tension, like a vacuum pulling water up the plant. This is how water can move up the tallest trees. So, we measure something called “water potential” to understand this tension. It tells us how much “pull” the plant has on the water. When there’s a difference in water potential between different parts of the plant, it’s like a driving force that makes water move from where there’s less pull to where there’s more. This helps water move up from the roots to the leaves, even against gravity. We call this whole process the “Soil-Plant-Atmosphere Continuum,” but you can just think of it as how plants drink water.

And that’s the basics of how water moves in plants!

Meet The Team

Meet the Team: Summer Harvest in the Nursery

Leave a comment

Regardless of temps in the high 80’s this week – !! – the season is wrapping up in the Nursery Program. We’ve had some notable events in these last few weeks, and we’re deep into planning our Fall/Winter workshops to keep up with the area growers and ever-evolving changes in the industry.

Event Success

Climate-Ready Landscape Plants Field Day 2023 hosted almost 30 volunteer participants in the north plots on the farm to assess the overall hardiness and beauty of ornamental varieties in various levels of drought.

Inspection of plant by 2 persons
Plants were assessed on floral presentation, health and vigor of foliage, and overall appeal.

Even under the threat of record high temperatures, Master Gardeners from all over NW Oregon arrived, as well as industry supporters, to enjoy the beautiful flowers and the misted tents. The OSU Nursery Program is part of a larger study on Climate-Ready Plant Trials throughout the Western US.

two people inspect one of the climate-ready varieties of plants
The ninebark varieties were unanimously considered particularly beautiful.

OTF STEM Teacher Training was led on the NWREC farm by the OTF STEM (On the Farm Science, Technology, Engineering and Math) Facilitators as a part of a larger tour including several farms and programs, including the Horticulture Program at OSU. Dalyn and Lloyd spent time with High School teachers from Oregon and Washington, demonstrating soil moisture sensors – both volumetric and tensiometer informed. In teaching the teachers, our program is better able to explain somewhat difficult material in a manner that makes it accessible at different levels of education and application. For example, Dalyn explained the differences between soil water holding capacity and plant-available field capacity and finding the permanent wilt point- the point at which plants in the soil will wilt, and can’t recover when water is re-supplied.

speaker addresses attendees outdoors
Dalyn discusses ground water and plant stress

Lloyd discussed vapor pressure deficits, or the effect of air temperature in drying plants, in relationship to atmospheric demand and plant responses to drought.

speaker addresses attendees
Lloyd addresses workshop attendees

Says Dalyn, “It’s really good for us and these teachers to meet like this to exchange ideas. Audience work isn’t usually part of a grant in Agriculture, but getting this information into classrooms helps to promote environmental sciences.”

image shows teammates lined up on the gravel pad at the farm
Members of the Nackley Lab posing for a team shot following the OTF STEM event

Drone Applications for Farm and Field kicked off our Smart Spraying seminar series, and was well attended here at the NWREC farm with over 50 participants on a cloudless fall day. NWREC’s Kristie Buckland opened the workshop with current research for uses of drone technology in application for smaller farms, followed by Andrea Sonnen of the ODA presenting on the regulations and requirements for aerial applicator licensing.

classroom full of students watches screen
Kristie Buckland discusses applications for drone use

We were happy to host Timothy King from Ag Drones West as he provided information about the DJI T40 Sprayer System and gave a spectacular show demonstrating both liquid and granular applications in one of our unused fields.

Timothy King explains the Operating System of the DJI T40 Drone Sprayer

This series continues in December with our second workshop titled “The ‘I’ in ‘IPM’: Integrating Approaches to Pest Management”.

Please visit our EVENTS page for information on upcoming workshops!

Nursery Knowledge

Nursery Knowledge: What’s in the Pot?

Leave a comment

Exploring Stratified Substrates and Soil Hydraulics in Agricultural Science

Lloyd Nackley

Nursery science researchers have embarked on a journey to harness the principles of soil hydraulics to reshape container production practices. In the past couple of years, Dr. Chris Criscione and Dr. Jeb Fields and others released a series of articles that showed that stratifying pine bark can serve as a substitute for peat-based media in floriculture and bark-based woody plant production. Through layering premium floriculture media over cost-effective pine bark within containers, they reduced reliance on peat. In their study focused on Petunia hybrid ‘Supertunia Honey’, the stratified substrates yielded crops of comparable size and quality, along with enhanced root productivity. Their work also showed superior performance of bark:coir substrates in a stratified setup, even when subjected to reduced irrigation when producing Loropetalum chinense ‘Ruby’ liners. Positive microbial communities in stratified systems further aided in mitigating water stress. Furthermore, Red Drift® rose plants grown in stratified substrates exhibited equal or superior crop growth despite receiving less controlled-release fertilizer. This suggests potential for reducing fertilizer and irrigation rates while upholding crop
quality, offering a sustainable avenue for containerized crops. This blog post aims to shed light on stratified substrates and also provide insights into ongoing projects at the Nackley Lab that are delving into this innovative frontier of nursery science.

image shows containers of growing medium of different textures
Image: mixing coarse and fine substrates in containers to address soil stratification

Soil hydraulics delves into the intricate world of water movement within soils—how water traverses the soil matrix, its distribution, and its intricate interactions with soil particles and structure. It’s a field dedicated to understanding the physics governing water’s journey through soils, and this knowledge carries significance for agriculture, environmental science, hydrology, and civil engineering. Soil hydraulics guides irrigation strategies, shapes drainage designs, and fuels sustainable land management practices.

image shows saturated and unsaturated soils in comparison
Image: water in saturated and unsaturated soils

Central to soil hydraulics is the concept of matric potential, a critical factor in irrigation management and plant-available water. Matric potential captures the degree to which soil particles retain water due to molecular attractions—it’s essentially the “stickiness” of water to soil particles. When soil isn’t completely saturated, minuscule air-filled spaces exist between particles. Water molecules adhere to these particles, creating capillary forces that coax water upwards. The strength of the bond between water and soil particles determines the matric potential, effectively influencing water availability to plants.

Image shows layering of the 3 soil phases: gaseous, liquid and solid
Image: the gaseous, liquid and solid phases of soils

Two other essential players in the realm of soil hydraulics are soil texture and structure. Envision soil as an intricate mosaic, with particles coming together to form aggregates, shaping distinct pathways and chambers. This arrangement, referred to as soil structure, creates macropores—
akin to express highways—through which water can flow rapidly. At the same time, micropores, reminiscent of narrow alleyways, gently retain water against gravity’s pull, acting as reservoirs
for plant roots during dry spells. Additionally, soil structure influences permeability, determining how efficiently water infiltrates and the risk of surface runoff.

Soil texture, on the other hand, hinges on the proportions of sand, silt, and clay particles in the soil. Each particle type comes with distinct traits that shape water dynamics. Coarser-textured soils with more sand have ample space between particles, allowing water to move quickly with
less retention. Finer-textured soils, rich in silt and clay, boast smaller gaps between particles, leading to slower water movement and higher water-holding capacity.

image shows the soil texture triangle
Image: The Soil Texture Triangle

However, when soil is confined to pots or containers, it undergoes transformations in its natural structure due to various container-related factors. The restricted space of a pot, contrasting with the expanse of natural soil, can lead to the erosion of soil structure. Aggregates—clusters of particles forming pores and pathways—can deteriorate over time due to limited expansion room. This confined space often results in compaction, where soil particles compress closely, reducing essential air-filled pores needed for root growth and water movement. The watering practices specific to potted plants can contribute further by compacting soil particles as water occupies gaps. The absence of natural soil organisms and plant roots within containers hampers the
maintenance of soil structure. Repeated disturbances, like transplanting or repotting, can exacerbate these structural changes. To counter these effects, selecting appropriate potting mixes that retain structure, incorporating organic matter for improved aeration and water retention, and being mindful of compaction during planting and watering are recommended.

image shows a hydrangea in a pot with drip irrigation
Image: Hydrangea in pot with drip emitter irrigation

Traditionally, the nursery field has focused on creating homogeneous potting mixes that maintain structure while offering suitable hydraulic properties. Classic blends often comprise bark, coir, peat, perlite, vermiculite, and pumice. However, a recent shift in focus has led scientists to explore how layering media can simulate natural soil hydraulics—an approach known as stratified substrates.

coarse substrate
Coarse substrate
fine substrate
Fine substrate

Stratified substrates involve arranging potting media of varying textures in layers within a single container. This structured layering entails placing coarser-textured substrates at the bottom and finer-textured ones on top, mimicking natural soil layers. This technique aims to influence water
movement, nutrient distribution, and hydraulic behavior within the confined environment of a container. By borrowing from the stratification seen in the ground, stratified substrates strive to
optimize resource efficiency, plant growth, and root development in controlled settings like potted plants.

Some may draw parallels between stratified substrates and the practice of placing rocks or gravel at the bottom of larger plant pots. While both concepts involve layering materials, there are distinctions. The practice of adding gravel or rocks to enhance drainage in larger pots shares a
kinship with stratified substrates. However, it doesn’t replicate the comprehensive layering dynamics seen in stratified substrates. Adding gravel mainly addresses drainage concerns without fully incorporating the layered hydraulic principles inherent to stratified substrates.

image shows 2 piles of substrates by texture
Image: fine (l) and coarse (r) substrate, side by side

Dr. Chris Criscione, in collaboration with the Dr. Jeb Fields group at Louisiana State University, has been at the forefront of investigating stratified substrates in containerized plant growth. Their research delves into how layering different potting media textures can enhance water retention, nutrient availability, and overall plant performance. The studies highlight promising outcomes, such as heightened root productivity, improved growth, and enhanced quality under stratified
conditions compared to conventional substrates. This technique holds potential for bolstering sustainable crop cultivation within controlled environments.

gravel pad with pots of hydrangea growing
Image: potted hydrangeas on the gravel pad at NWREC

Nevertheless, it’s crucial to acknowledge that findings from studies conducted in one geographic region—such as the Southeastern USA—may not seamlessly extrapolate to other areas with distinct climates and environmental conditions, like the Pacific Northwest. Climate, temperature, humidity, and other factors can significantly influence plant growth and water dynamics. Given this variation, research in regions like the Pacific Northwest, such as Oregon, is crucial. The
unique environmental factors there, including cooler temperatures and higher rainfall, can impact water movement, nutrient availability, and plant response to stratified substrates. Bark-based substrates, common in some areas, may behave differently in terms of water retention and
drainage in regions with distinct soil compositions. To address this, the Nackley Lab initiated a collaboration with Dr. Fields and others in 2022, planning to explore the impacts and benefits of stratifying substrates in Nursery production. The first stratified substrate experiment was
launched in 2023 at Oregon State University North Willamette Research and Extension Center (NWREC), aiming to reduce resource demand and provide insights into the effectiveness of stratified substrates in that context, contributing to more informed decision-making for nursery production and horticulture practices in the region.

More Information:

Evaluating Stratified Substrates Effect on Containerized Crop Growth under Varied Irrigation Strategies

Root Exploration, Initial Moisture Conditions, and Irrigation Scheduling Influence Hydration of Stratified and Non-Stratified Substrates

Single-screen Bark Particle Separation Can be Used to Engineer Stratified Substrate Systems

Stratified Substrates Can Reduce Peat Use and Improve Root Productivity in Container Crop Production

Irrigation, Meet The Team, Plant Health

Meet the Team: Summer Update

1 Comment

The Gravel Pad update you’ve been waiting for, and more!

There’s so much going on in the season of plenty around NWREC! Enjoy this virtual tour of a few projects around the nursery.

Dalyn has been continuing her work with mini-lysimeters that control irrigation in shade trees – these tiny scales weigh the potted plants and use the change in weight as they dry to determine when to turn on the water. The lysimeters are gathering data on plant weight along with an on-site weather station to better understand the relationship between heat and irrigation in gravel pad production. Read more about this project here.

View of gravel pad with potted maple trees
Young red maple trees on the gravel pad are using lysimeters to monitor water loss in conjunction with a dedicated weather station (left).

The Willamette Valley has had a few HOT summers in a row, even though lately this one has been pretty mild. Nevertheless, we haven’t given up on finding solutions for heat mitigation – including growing ornamentals under drought conditions to see which are the most “climate-ready” to meet changing needs. We’ll be asking the public to evaluate those plants in the upcoming Climate-Ready Field Day, come along and see how the plants are progressing (click the link above for more info).

In addition, we’re evaluating different means of mitigating the heat and the resultant high rates of evapotranspiration (basically ways to reduce plant sweat), from misting the young plants to covering tissues with kaolin, introducing fungicides that may be beneficial in managing water loss, using white pots instead of the traditional black, and even growth inhibitors – it’s been a pretty amazing feat to monitor the effects as you can see- check out this monitoring station!

Jaiden, Lloyd and Dalyn at the ET monitoring station with shade trees
Dalyn, Lloyd and summer hire Jaiden show off the monitoring station in the heat stress/evapotranspiration mitigation study.

young flowering shrubs in alternating black and white pots
Does the color of the pot change the heat stress for these water-loving shrubs on the gravel pad?

A small project growing marigolds for festivals and holidays – like Dia de los Muertos – is also underway. Growing the marigolds has certainly brightened up the Nursery Zone at NWREC, and we’ve progressed into evaluating passive means to dry the flowers, saving energy and resources while preserving the gorgeous summer color.

fresh marigolds
Marigold blooms
dried marigolds

There’s even more in the works – stay tuned for information about fall workshops and PACE courses created specifically for nursery and greenhouse production for topics covering drone sprays, integrated pest management, and more.