Climate Change – Maryland Grows

New Year, New Habits on the Horizon

January 16, 2025Maryland GrowsLeave a comment

I’ve been thinking a lot about habits lately—a whole lot. Changes in just one or two simple habits can radically transform our personal lives, society, and how we relate to the natural world, hopefully for the better but sometimes for the worse. How many of us have made a resolution or started a new habit already this year involving nature, gardening, or land stewardship? Are you sticking with it or just getting around to thinking about starting it? I am here to say: “If it matters, don’t give up!” It can take time and practice through repetition to establish or change a habit, according to an accumulating body of fascinating research around the human psychology of habits. A little bit of knowledge about how habits work can go a long way toward establishing and maintaining new habits.

The habit loop

Habits are a big part of what powers us through the day without having to think through the details of each and every step in a routine action. From wake up routines to commuting patterns, we carry out a series of regular actions based on established and regularly repeated cues, routines, and rewards. This is known as the “habit loop,” as vividly described by Charles Duhigg in his best-selling book, The Power of Habit: Why We Do What We Do in Life and Business.

Duhigg describes how habits, deeply encoded in one of the most evolutionarily ancient parts of our brains, the basal ganglia, relieve us of some of our daily cognitive load so that the more advanced parts of our brain can be devoted to higher order activities like reasoning, innovation, and decision-making. Habits can become ingrained fairly quickly if the chemical neurotransmitter reward in our brains is great enough, if the cues and rewards are strongly linked, or when routines are simplified and reinforced through regular repetition and behavior reinforcement.

A square illustration of the habit loop showing a human eye on the left, representing the cue. Above the eye is an arrow that makes a right turn at the top of the illustration and connects with a scrub brush representing the routine of cleaning the birdbath. An arrow flows from the brush and turns downward to a pair of binoculars, a bluebird, and a red heart symbol and exclamation point representing the reward of seeing a bluebird. An arrow continues downward and curves left to form the bottom of the illustration, connecting back to the human eye.

Caption: An example of the habit loop illustrating part of my winter bluebird care routine. I spot a messy bird bath after a day of heavy use (visual cue), spring into action to scrub the basin and refill with clean water (routine), then enjoy the thrill of spotting a bluebird taking a drink of fresh, clean water the next morning (reward). My craving to see bluebirds in winter helps to power me through this frequent winter routine on freezing cold days. I suspect some endorphins are released in my brain every time I witness the scene of a bluebird drinking fresh water outside my window on a freezing cold winter day. Graphic: S. Small-Lorenz

Cue-routine-reward. Cue-routine-reward. A habit cycle powered by an incessant craving for a drop of neurotransmitter joy. Habits can become so routinely mechanized that they are difficult, yet not impossible, to change. It is entirely possible, though, to modify habits just through tweaking routines. It is also possible to create new habits through repetition, with clearly identified cues and rewards. To instill a new habit, it can help to establish the cue, the reward, and a simple sequence of action steps in between.

Black plastic trash bag in the gutter with leaves spilling out of it

These habits also reflect missed opportunities to create better soil with higher soil organic matter that absorbs more stormwater where it falls, which would result in a more flood and drought-resilient watershed because soil with higher organic matter absorbs and retains more moisture. This, in turn, creates a foundation for a flourishing landscape that supports a wide array of biodiversity.

Keystone habits: Small actions that lead to big results

Then there are habits known as “keystone habits.” Like the architectural feature that supports an arch or keystone species that sustain an ecosystem, keystone habits are those habits that have the power to make big change throughout a system, by means of small actions. Small action = big change. It sounds so simple and gratifying, right? But is it realistic?

Duhigg gives examples of successful organizations and individuals who have identified and implemented keystone habits to achieve positive change and desired outcomes. These include daily habits drilled by Michael Phelps that helped him to break a world swimming record in an Olympic race, even while his goggles failed him, and former Alcoa CEO Paul O’Neill’s singular, unprecedented obsession with workplace safety that dramatically transformed its corporate culture and overall productivity, despite initial deep doubts and laments of indignant shareholders. Think about a life-altering habit that you have adopted, changed, or left behind. How hard was it but how much did it transform your life to eventually change that habit? Research has shown that cues and rewards of the habit loop can be difficult to rewire, but that it is also entirely possible to alter the routine between the cue and reward to achieve a more desired outcome.

My primary driving question these days is: “How do we change habits to improve habitat?”

As I review the many sustainable practices promoted through our Bay-Wise Living Landscapes Program, I am searching for those potential keystone habits that we should emphasize in 2025 that represent small actions for big changes. Small behavior changes across the landscape that, when added up, could have an outsized, beneficial impact on our watersheds and their ecosystems.

My 2025 keystone habit for Maryland

If I could foster one keystone habit change across Maryland in 2025 it would be this: “Recycle yard debris on-site.” This one habit actually captures a number of low-cost but beneficial practices, such as leaving leaf litter where it falls, leaf mulching, grass-cycling, and creating wildlife brush-piles from yard prunings. So, technically, we’re talking about habits within a habit.

The photo shows fallen tree leaves partially covering a lawn area.

The photo shows a log exposed under a layer of snow.

Caption: Leaf litter (L) and a log under a layer of snow (R). Firefly larvae take shelter in leaf litter and logs throughout the winter. Yard “debris” has high habitat value, providing overwintering habitat for many beneficial insects and wildlife species. Photos: S. Small-Lorenz.

Managing our yard “debris” like leaves, grass, clippings, branches, stumps, snags, and prunings in ways that acknowledge their ecological value can improve soil and water, laying the groundwork for more climate-resilient landscapes and communities. Leaving leaves where they fall nourishes soil and vegetation, retains soil moisture, creates a substrate for native plants to establish, and provides an insulating ground layer of habitat for a wide array of species.

Leaf mulching and composting on-site are other sustainable options for managing leaf litter. Grass-cycling by leaving grass clippings on the lawn instead of bagging it up and sending it off-site provides a free, natural fertilizer with a much lower carbon footprint than trucking it off or applying manufactured fertilizer. Arranging downed limbs and pruned branches into brush piles provides shelter for songbirds and small mammals on extended snowy days like we’ve had this month and throughout the year and returns carbon and nutrients to the soil. (The main exception to this habit is to remove and properly dispose of invasive non-native plant materials, especially those that reproduce vegetatively or have gone to seed, to avoid spreading them.)

Photo of a small brush pile in deep snow, surrounded by animal tracks. — Caption: Brush pile in deep snow, surrounded by animal tracks.
Photo: S. Small-Lorenz

How does habit change take root in the community?

However, pleading with people or even providing scientific evidence is not likely to make these habit changes take hold on a large enough scale to make a measurable impact across an entire watershed. Study upon study has shown that people are more likely to respond to a combination of seeing their neighbors do it and financial incentives over any amount of urging, pleading, pledging, or piles of scientific evidence (Bergquist et al. 2023). Could this be because neighbor cues and financial rewards better tap into this primal habit loop of cue-routine-reward? There is evidence that the answer to this question is “yes.”

Friction, cues, and incentives

In a fascinating review, Mazar et al. (2021) identified three successful strategies for motivating environmental behavior change through policy, and I believe these strategies are applicable to individuals and organizations as well. First is the strategic use of friction. Identify where friction can be reduced or increased to motivate habit change. Make it easy to implement the desired behavior (reduce friction) or a little more challenging to do it the old way (add friction). They cite a number of environmental behavior change studies, including one that made it easier to recycle by reducing steps to the recycling bin or a little more expensive to use disposable bags through token bag fees. This is a matter of simplifying the routine in the cue-routine-reward habit loop to lead to the desired behavior or complicating it to deter less desired behavior.

A bright blue male Eastern Bluebird points his bill upwards as he drinks clear water from a bird bath during a heavy winter snow. An inkberry holly next to the bird bath holds several inches of snow on its foliage.

“Re-setting the default” is a related strategy. A variety of studies have shown that setting the desired behavior as the default results in more rapid and widespread adoption of the more environmentally friendly option. For example, placing vegetarian meals at the top of a menu or adjusting office thermostat default settings resulted in significantly higher uptake of the desired pro-environment behaviors. In a different but related example, if I see salad at the start of a buffet meal, I will undoubtedly fill my plate with a bed of greens. If I encounter the dessert table first, you’d better believe I’m starting with the cheesecake!

Second is implementing clear cues to action – for example, studies showed that improving signage on cafeteria recycling bins using clear visual symbols right at the disposal site resulted in positive environmental behavior changes. I see this as directly tapping into the cue part of the cue-routine-reward habit loop.

Third is psychologically informed incentives that steer people toward desired environmental habits or away from detrimental habits. It turns out that people really like and value free things. Small fees, like the bag fee, have resulted in major societal behavior shifts by imposing a very small cost on the behavior of accepting a disposable bag. My local natural foods store takes it a step further by offering a wooden nickel token for each reusable bag a customer deploys, to donate to their choice of three local charities. There’s a double reward to accelerate that cue-routine-reward habit loop. Save the bag fee and donate it on the spot to a charity making a positive impact in the community.

Savor the intangible rewards

Rewards don’t always have to be financial, although small financial rewards or rebates have been shown to motivate environmental behavior change on a societal level. Rewards may come in the form of cost and time-savings or they may be as intangible as the smell of rich organic soil that you and your tree co-created, the endorphins released during the exercise of planting a common witch hazel shrub, the pleasure of seeing an Eastern Bluebird take a drink of fresh water from your clean, heated bird bath on a freezing winter day, or the joy of sighting that first firefly flicker of June.

Photo shows leaf litter, prunings, and standing woodland sunflower stems in the winter during a January snowfall event.

Photo shows leaf litter and songbird tracks in a light layer of snow.

Captions: Top: leaf litter, prunings, and standing woodland sunflower stems in the winter during a January snowfall event. Bottom: litter and songbird tracks in a light layer of snow. Photos: S. Small-Lorenz

If we can get comfortable with a slightly rougher and wilder aesthetic in our residential landscapes, the biodiversity and climate-resilience benefits could be immense. These new habits lend themselves to creativity – you can be as messy, manicured, or artistic as you would like with them yet still enjoy the benefits of rich soil, sustained soil moisture, pollinators, songbirds, hawks, and owls in your yard or park.

If you have resolved to become a better steward of nature this year, or even if you are just now thinking about trying your hand at some aspect of ecological landscaping, try putting your new knowledge of the habit loop to the test. If you’re looking for a place to start, join me in recycling your yard waste on-site in 2025. It may take a while to adjust and get the hang of this way of doing things, but once you get in the habit loop by identifying your cues, routines, and rewards, I predict that the workload becomes lighter, the cost savings will add up, and the many intangible rewards of being a better watershed steward right where you live will be noticeable and energizing.

References

Berguist, M. M. Thiel, M.H. Goldberg, S. van der Linden. 2023. Field interventions for climate change mitigation behaviors: A second-order meta-analysis. PNAS 120(13).

Duhigg, C. 2023. The Power of Habit: Why we do what we do in life and business. Penguin Random House. New York.

Mazar, A., G. Tomaino, Z. Carmon, W. Wood. 2021. Habits to save our habitat: Using the psychology of habits to promote sustainability. Behavioral Science & Policy, 7(2). Pp. 75-89.

By Stacy Small-Lorenz, Ph.D., Residential Landscape Ecology Specialist, University of Maryland Extension. Read more posts by Stacy.

Sustaining Hope: How Will the Chesapeake Bay Watershed Weather the Next Helene?

October 1, 2024October 3, 2024Maryland Grows4 Comments

The news out of the southeastern US following Hurricane Helene is heart-wrenching. Up to a foot of heavy rain fell on saturated soils across mountainous western North Carolina, in the fallout of a hurricane that made landfall in Florida but dumped 40 trillion gallons of rainwater across several states.

Aerial photo of Tropical Storm Helene flood damage in North Carolina. Photo credit: Sgt. 1st Class Leticia Samuels, US Army National Guard

Inland communities were not spared from this coastal storm that sent torrents of water through mountain towns, leaving a wake of wreckage in its path. Roads, bridges, and buildings have collapsed under the force of debris-laden flood waters throughout the region.

Airlift rescues and supply drops are underway, but many residents remain cut off, and countless are yet unaccounted for across the region at the time of writing. The Federal government has issued Major Disaster declarations for areas of North Carolina, South Carolina, Florida, and the Eastern Band of Cherokee Indians. Marylanders hold all affected by this powerful storm in our hearts and stand ready to support their recovery.

Extreme precipitation events like this are becoming a new norm, brought about by increasingly powerful storms carrying more water, driven by the heat energy of warmer-than-average sea surface temperatures. Hurricanes and tropical storms forming over warmer waters of the Atlantic Ocean and Gulf of Mexico contain more energy and hold more moisture, with the potential to bring record amounts of rainfall anywhere throughout the Southeast, Mid-Atlantic, and New England regions. Tropical Storm Helene reminds us again that inland and upland regions can still be devastated by coastal storms. The Chesapeake Bay Watershed is no exception.

Animated satellite image of Hurricane Helene. Source: NWS/NOAA

It is with all of this and more on my mind and in my heart that I assume the new role of Residential Landscape Ecologist at University of Maryland Extension. I look forward to advancing green strategies that reduce flood risk and pollution from stormwater runoff into the Chesapeake Bay while enhancing biodiversity. This work is vital to addressing the most extreme impacts of climate change like floods, heavy precipitation, heat waves, and drought. We can do it in ways that reduce greenhouse gas emissions as well and bring a great deal of joy to our lives and communities while we’re at it. The Maryland Bay-Wise Landscape Management Program encourages widespread and strategic uptake of nature-based practices that improve water quality and reduce flood risk.

In this position, I will work closely with university colleagues, agency and NGO partners, and Maryland residents to promote sustainable landscape practices that contribute to a healthy and climate-resilient Chesapeake Bay Watershed. Efforts to retain, slow down, and filter stormwater using native plants and landscaping strategies like rain gardens, pollinator gardens, forest conservation, and riparian buffer strips can help reduce the overall amount of water running off from lawns and impervious surfaces like rooftops and asphalt. Allowing more rainwater to be absorbed where it falls reduces and delays flood peaks downstream while ensuring cleaner water for aquatic species and habitat for beneficial insects, declining songbird populations, and other Maryland wildlife.

Here in this space, I look forward to sharing perspectives on emerging science and trends in climate-resilient sustainable landscapes, environmental horticulture practices and gardening for wildlife, and dialogues with bearers of traditional knowledge – getting my own hands dirty along the way as I share some of my personal experiences with conservation landscaping in my wild corner of the Earth.

I am deeply grateful for the opportunity to join you and my Extension colleagues on this important journey, as there is vital work to be done to ensure a healthy and sustainable future for Maryland communities.

If you would like to help those impacted by Hurricane Helene, Charity Navigator has compiled this list of highly rated organizations providing relief assistance for those affected. Emergency resources for those in the impacted area and their families can be found at FEMA.gov.

By Stacy Small-Lorenz, Agent, Residential Landscape Ecology, University of Maryland Extension.

Heat Waves Affect Pollination Too

August 5, 2024March 7, 2025Maryland Grows2 Comments

Having grown up in the plains of Argentina, surrounded by large rivers, swamps, hot summers and humidity, I can attest that I am pretty “heat tolerant.” While others complain of the heat, I just enjoy the “embrace” that a hot day gives me. The heat in the last few weeks, however, was even too hot for me! And while I was trying to cool down, I was also worrying about what I was seeing outside: the plants, the insects, the soil… all suffering like me. And because I happen to work on some of these topics, I also knew that it wasn’t just that some plants were drying out; this heat wave (and drought) is also affecting the whole network of interactions that happen around us. So, today let me tell you a bit about how these extreme heat waves affect one of those interactions – pollination – and how what we do in our green spaces can help reduce some of those effects to the benefit of all.

Pollination is affected by heat in more ways than we usually think

Extreme heat waves and droughts such as those we have been experiencing recently affect not only us but also the ecosystems that are exposed to the heat. One of the most evident effects we may see is how much plants suffer. Just look outside and you will see hanging leaves, tiny flowers (if any), and a lot of dry material. As with all organisms, plants also have optimal temperatures at which they can survive; if the temperatures and water availability change, important body functions will not be able to be performed, and even some central parts of their bodies will fail.

In plants, one of those functions is photosynthesis, the process by which plants can make sugar using the energy of the sun, carbon dioxide (CO₂), and water. This process is the way the vast majority of plants make their food. If the process is disturbed, the plant will have less energy available to survive, grow, and reproduce. It turns out that extreme heat and water needs affect the ability of plants to photosynthesize. The consequence of this is that, suddenly, the plant has less energy available, needing to enter a sort of “survival mode.” Along with this, the heat affects several protection systems that the plant has, especially those that protect the DNA (the genetic material), as well as the functioning of the machinery that literally “builds” the different parts of the plant. This inefficient protection leads to the DNA being damaged and the plant being poorly “built”, making that part or the whole plant start malforming.

plants with browing stems due to drought — *During the heat waves, these beebalm plants had a rough time, with almost no flowers produced and a lot of the plant material simply drying out. Photo: A. Espíndola*

In relation to pollination, we know that these changes explain why, under heat and water stress, plants become smaller in size, have tiny or no flowers, lose a lot of leaves and biomass in general, and have parts that start to look “funky.” The changes in the energy availability make the composition of some secretions change as well, such as with nectar, which tends to be less rich in sugars and less abundant (especially when drought is experienced).

a plant with smaller than usual yellow flowers — *These black-eyed Susans were able to make flowers this year, but they are significantly smaller than usual! Photo: A. Espíndola*

As said before, flowers tend to be small or absent, but even when they are present, the petals and reproductive organs are often misshapen, with the plant becoming unable to produce seeds and fruits. Finally, and super importantly for pollination, a major effect of this is that heat affects pollen quality, reducing the amount that is produced and often making the pollen inviable… meaning that even if the pollen was to land on a stigma, it would likely not germinate, and fertilization would not take place. This latter point is worrisome because it means that even plants that are not animal-pollinated (e.g., plants pollinated by wind or water) will be unable to produce seeds and fruits.

Pollinators suffer the heat, and that affects their survival and pollination

Pollinating insects are also affected by the heat, and some of these effects are related to the same facts we mentioned for plants. On the one hand, like plants, pollinators also have their own DNA and “body-building” machinery that is disturbed by heat. Some of the major consequences of this are that their development can be either interrupted (the larvae or pupae die off) or interfered with. If the development is interfered with, we see malformations in different organs, such as the wings, legs and mouth parts, and particularly in males, of reproductive organs and sperm. Further, extreme heat appears to affect bee neurological abilities, with their behaviors and memory affected, as well as changes in the way they visit and manipulate flowers, which in turn makes pollination more difficult.

Along with these issues, because of the changes in nectar quality and quantity associated with plant heat stress that we mentioned earlier, the pollinators’ nutrition is also negatively impacted, which further amplifies the developmental, behavioral, and neurological problems mentioned above. Although all insects experience these types of effects when they are exposed to excessive heat, some of them are a bit better at protecting themselves from it. For example, it seems that social bees suffer less from excessive heat than solitary bees, while bees that nest in the ground or in stems tolerate it better than those that nest in cavities.

Here’s what you can do to help mitigate the effects of heat and drought

Although we can’t instantaneously reduce the heat, we can assist plants and insects to better tolerate these conditions. A very effective strategy is diversifying our green spaces, which can lead to local reductions of heat, either through the shade created by the plants and/or the reduction of the excessive presence of bare soil. In particular, this same plant diversification can also increase the amount and quality of foods available to pollinators during these heat events: more diverse plants mean more different types of possible nectar sources available to pollinators, which in turn would increase their chances of survival and boost their health.

If possible, one can also water plants in our green spaces. By doing this, the water stress will be reduced and at least part of the symptoms displayed by plants will also be mitigated. If one were to do this, it is important to water with a slow flow and for a longer period of time, so the water can properly enter the soil. Along with this, using mulch or letting the fallen leaves cover the ground will also help retain some of the soil humidity, all while also providing shelter to insects.

And besides diversifying and supporting our green spaces, it is thoroughly accepted that the current extreme heat and drought events we are seeing are a consequence of climate change. Starting to reduce our and our communities’ emissions is another way to help plants and pollinators, pollination, and at the end of the day, the production of many of the foods we depend on. You can check out this awesome website by Dr. Sara Via and learn about what we can all do, and even sign up for super informative seminars that help you become familiar with and start acting on some of these topics.

By Anahí Espíndola, Associate Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

Smart Watering Helps Plants Beat the Heat

July 26, 2024March 7, 2025Maryland Grows4 Comments

Cole Porter was right. It’s too darn hot.

As we watch the high temps stubbornly refuse to budge, it’s tempting to hunker down indoors and let our gardens go. Don’t. Those plants really need us now.

The best thing you can do to help is to water well. That means watering deeply less often.

a show of water from a hose - watering a garde plant — Water at the base of plants to soak the roots.
Photo: Miri Talabac, UME

Daily sprinkles do more harm than good, stimulating shallow roots, which have a harder time drawing up the water plants need.

Light watering also encourages tomatoes and peppers to develop black, leathery blossom end rot.

So water vegetable plants deeply twice a week. Dial it back to once a week when things cool down.

Watering in the morning is best as is directing water to the base of plants.

If you planted new trees or shrubs this year, water them slowly and deeply at least once a week to soak the root ball. Use a soaker hose, a 5-gallon bucket with a few nail holes, or a hose on a slow trickle.

a green tree bag placed around the trunk of a tree — Tree bags help to keep trees and shrubs well watered.
Photo: Joe Murray, Bugwood.org

And no, rain is not enough. Here are a few more tips on watering trees and shrubs.

If you’re growing anything in containers, check those pots daily. Most need to be watered every day. And do some supplemental watering in your perennial beds. Everything is dry, dry, dry.

Smart tools make watering easier and use less water.

Soaker hoses – made from recycled tires – water plants slowly at the base of plants so you don’t lose water to evaporation.

Drip irrigation does the same and lets you customize water zones. I can’t say enough good things about the drip irrigation system on a timer in my vegetable beds.

a drip irrigation system set up in a raised bed garden — Drip irrigation saves time and money.
Photo: Robert Cook

Rain barrels are a godsend. An eighth of an inch of rain on the average roof fills a 50-gallon barrel. That’s free water, folks. I have four rain barrels and plan to add two more.

a rain barrel next to a garden — Rain barrels capture rain from roofs to reduce water bills.
Photo: Rutgers University

Avoid watering with sprinklers. Overhead watering can promote disease and cause the loss of up to 80 percent of water to evaporation.

Here are some more tips on conserving water and using smart tools.

In addition to boosting plants’ water needs, heat zaps plants in other ways.

Have you noticed flowers falling off your tomato plants? Sustained high temps prevent pollination, causing plants to jettison their blooms. Don’t worry. Flowering and fruiting will restart when it cools.

Trees react to high heat, too. Many are raining down leaves. This is a natural stress reaction. In fact, trees don’t need all their leaves. They’re just shedding some to cut down on maintenance.

Unless the leaf loss is dramatic, those trees will be just fine.

Lawns are feeling the heat as well, browning here, there, and everywhere. They are not – I repeat not – dead. Lawns naturally go dormant in high heat and will spring back with rains. Only new lawns need to be watered.

If you’d like to boost your landscape’s resistance to heat and drought – and the need for supplemental watering – add some water-wise plants.

Deep-rooted, well-adapted native plants are a great choice. So are plants with fleshy leaves or roots, blue leaves, skinny or fuzzy leaves – all natural adaptations that mean these plants need less water. Think sedum, iris, lavender, threadleaf coreopsis, and lamb’s ear.

Here are some tips for creating a more climate-resilient landscape.

Watering wisely and picking the right plants will help you build a more heat-resilient landscape that can not only beat the heat but look good doing it.

By Annette Cormany, Principal Agent Associate and Master Gardener Coordinator, Washington County, University of Maryland Extension.

This article was previously published by Herald-Mail Media. Read more by Annette.

Free the Flare: Maintain Visible Root Flare for Tree Health

January 12, 2024April 14, 2026Maryland Grows5 Comments

Tree planting efforts are picking up as Maryland’s 5 Million Trees Initiative moves forward in 2024. Getting these trees – any landscape trees – off to a good start at planting time and through their first few years of establishment is important for their long-term growth and benefits to the environment.

At Ask Extension, we often receive photos of newly planted trees and older specimens with signs and symptoms of trouble. One of the things we do in our diagnostic process is look to see if there is a “root cause.” Is a girdling root present at the base of the tree trunk? Is the tree planted too deeply? Can we see a root flare? Today I want to bring these questions to the surface and explain why an exposed root flare can help prevent the formation of girding roots and why it matters for tree health and pest management.

a beech tree with a nice sloping visible root flare above the soil line — A beech tree with normal, healthy root flare. Photo: Miri Talabac, University of Maryland Extension (UME)

What is a root flare?

The root flare is the area at the base of a tree trunk where the topmost roots emerge outward. This area is sometimes referred to as the trunk flare or root crown. In many species of trees, the trunk widens and curves outward (“flares”) like the base of a wine glass. This is illustrated nicely in this brief video by the University of Maryland Arboretum and Botanical Garden’s Outreach Coordinator, Meg Smolinkski.

What is the root flare of a tree?

When thinking about the trunk and root system of a tree, it is important to keep in mind: Roots need to be in the soil to get a steady supply of moisture and nutrients. The trunk (stem) portion should be out of the ground where exposure and good airflow help to keep the bark dry.

In our landscapes, we have many trees that are planted too deeply and the root flare is not visible at all. The trunks go straight into the ground like telephone poles. This can result in lower bark rotting, reduced oxygen supply to the roots, disease and pest problems, and girdling roots.

We have an epidemic of planting trees too deeply

At the University of Maryland Extension Advanced IPM Conference for the commercial horticulture industry last month, Jacob Hendee, an arborist for the Smithsonian Institution Gardens, talked about how common it is nowadays to see trees planted too deeply. Burying the root flare has reached “epidemic” proportions in our landscapes, he noted – and it is killing trees.

The main problem he addressed in his talk was that buried root flares can set the stage for stem girdling roots to develop unnoticed. Stem girdling roots (SGRs) grow around the tree’s base, rather than pointing outward away from the trunk as normal roots should. As girdling roots grow and enlarge, they compress the water- and nutrient-conducting tissues in the tree. This interrupts normal plant functions and can lead to symptoms such as leaf yellowing (chlorosis), smaller-than-normal leaves, leaf scorch (browning), branch tip dieback, and bark cracking. SGRs can and do result in overall tree decline and eventual failure.

girdling roots are present at the base of a tree that has too much mulch — An example of girdling roots. Photo: M. Talabac, UME

An illustration showing the growth of sapwood in a tree - In year 5 it is all sapwood, in year 10 the sapwood outlines the heartwood and in year 15 there is a larger ring of sapwood on the outside circumference — Looking at a cross-section of a tree trunk, the light-colored portion is the water-conducting sapwood (xylem). Source: Jacob Hendee, Smithsonian Gardens

An illustration showing how a stem girdling root grows around a trunk and constricts - limits the growth of the water conducting xylem ring — When a stem girdling root forms around the trunk of a tree (represented in orange in the diagrams), it compresses and kills the water-conductive sapwood, which can result eventually in a dead tree. Source: Jacob Hendee, Smithsonian Gardens

Trees under moisture stress due to stem girdling roots become more susceptible to pests and diseases. Scale insects are significant pests of some landscape trees, as are some types of beetles and other insects. If a tree develops a pest issue, the pest may be secondary to the problem that made the tree vulnerable to the pest in the first place – stress.

Hendee emphasized that maintaining a visible root flare and preventing SGRs are practices of Integrated Pest Management (IPM). IPM involves using physical, cultural (plant care), and biological methods to manage pests and diseases, leaving chemical pesticides as a last resort. In the example of tree care, correct planting and monitoring to prevent stem girdling roots are key steps to preventing tree stress. Instead of thinking about killing secondary pests that show up on trees, think about how to prevent stressful growing conditions from the beginning and during the life of a tree. Trees with minimal stress are more resilient to insect pests and less likely to be overwhelmed by them or need intervention to recover.

How do stem girdling roots get started?

Hendee noted that plant care practices, both before planting (at the nursery), during planting, and afterward (over-mulching) contribute to this problem.

1. Many trees are grown too deeply in the nursery. Girdling roots can start to form inside nursery pots when the roots hit the container and start circling. This issue can worsen when young trees are moved into larger containers as they grow (such as saplings being transplanted into a bigger pot as they mature) and their roots are not loosened or pruned to correct deformities. Larger trees are sometimes planted too deeply in the nursery field and come to the customer in “ball and burlap” form with the root flare already covered in soil.

2. Many trees are planted too deeply at the time of installation. If the planting hole is dug too deeply, the root flare gets buried when the soil is filled back in, and often then further covered with mulch. In that situation, stem girdling roots can develop and worsen undetected.

3. Tree flares are often buried deeply in mulch. Too often we see huge piles of mulch – sometimes one foot high or more “mulch volcanoes” – around trees. This will keep the bark moist and can encourage new roots to sprout from the trunk above the main supporting roots (the flare). Those adventitious roots will grow upward for oxygen and may begin to girdle the flare and trunk. They will also be more vulnerable to moisture stress since the mulch does not retain water in the same way soil does. There is absolutely no horticultural basis for putting a big mound of mulch around a tree like this!

Mulch piled over 1 foot high around a young tree near a parking lot - there is no visible root flare - this is a mulch volcano — An example of incorrect mulching. Photo: Dr. David L. Clement, UME

mulch was incorrectly placed on top of a girdling root around the base of a tree — Here fresh mulch was incorrectly placed on top of a girdling root and up against a tree trunk. Photo: C. Carignan, UME

What can you do? “Free the Flare”

1. Check the roots at planting time.
If you purchase a container-grown tree, ensure it is free of circling roots inside of the pot. If you do find roots that are circling the root ball, cut through those roots with a pruner or other sharp tool. Set the roots in the planting hole so that they are pointing in an outward direction.

Prevent girdling roots when planting a container-grown tree

2. Keep the top of the root flare visible.
Root flares should be above the soil line. Plant so the root flare is 2 to 4 inches above grade. When purchasing a container-grown or burlapped tree, you may need to wash away some of the soil to see where the root flare begins. If a landscaper is installing a tree for you, make sure they set the tree at the correct depth.

soil from a container-grown tree was washed away to reveal that the top of the root flare had been sunken too deeply in the pot — A hose was used to wash away the soil from a container-grown tree, revealing the top of the root flare. The difference in the lower bark color (on the trunk) indicates that the plant was several inches too deep in its container. Photo: M. Talabac

When a root flare is visibly present, it can help deflect any stem girdling roots that begin to grow, forcing them away from the trunk. It also makes it easier to see where girdling roots begin to form. Monitor the root flare area of your tree(s) regularly and cut through any circling roots that begin to grow. It is easier to cut wayward roots when they are small. The process of locating and remediating stem girdling roots on older trees can be very expensive.

Also note that some species of trees are more prone to developing girdling roots (e.g., maples), and sometimes girdling roots develop below the soil surface where they are not easily detectable except by above-ground clues. If you see symptoms of water stress in the canopy of an otherwise sufficiently-irrigated tree (e.g. leaf scorch, smaller-than-normal leaves), consult with a certified arborist for a tree assessment.

3. Don’t overdo it with the mulch!
Keep a mulch-free buffer zone around the root flare. Hendee suggested leaving a 3 to 12-inch area bare around the base of the tree. Think of it as a donut hole: mulch should be laid down in the shape of a wide, shallow donut rather than a big heaping mound. The total depth of the mulch should be only about 2 to 4 inches.

how to mulch correctly - free root flare - mulch free buffer around the base of the trunk - 2-4 inches of mulch depth - broad mulch width — Mulch applied correctly. 1 Free root flare, 2. Mulch-free buffer around the root flare, 3. 2 to 4 inches mulch depth, 4. Broad mulch width. Infographic by Smithsonian Gardens

For further exploration of these topics and correct tree-planting procedures, I recommend the following resources:

Show Me Your Root Flare (PDF) | Clemson University

Girdling Roots | University of Maryland Extension

Planting and Care of Trees | University of Maryland Extension

Problems With Over-Mulching Trees and Shrubs | Rutgers

By Christa Carignan, Certified Professional Horticulturist & Coordinator, University of Maryland Extension Home and Garden Information Center. Read more posts by Christa.

Illustrations used with permission from Jacob Hendee, Smithsonian Gardens

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Composting and Climate Change

September 25, 2023September 22, 2023Maryland Grows3 Comments

Composting is probably seen by most people as good for gardens and the environment. After all, compost helps make our soils and plants healthier and keeps green waste from our yards and kitchens out of landfills.

But is composting good in the context of our climate crisis? Doesn’t the composting process generate lots of carbon dioxide (CO₂), the principal greenhouse gas (GHG) that traps heat in Earth’s atmosphere? Can composting also mitigate climate change and make our yards and landscapes more climate-resilient? The answer to both questions is YES. This article will show that composting, at the home, community, and municipal/commercial level, is an important global warming mitigation and adaptation tool. As we’ll see, the ways that humans manage this natural process and use the compost can affect the climate benefits.

Composting basics

We don’t make compost! Huge populations of microorganisms do most of the work and we humans manage the process for our benefit. It’s nature’s way of recycling anything that lives and dies, like plants, animals, and microbes.

The decomposition process produces lots of carbon dioxide (CO₂), part of the world’s carbon cycling system shown in this graphic:

illustration of the carbon cycle - plants use carbon dioxide from the air and water from the soil to build carbohydrates — Plants exude carbohydrates through their roots to feed soil organisms. Those organisms release carbon dioxide through respiration. Illustration by Jocelyn Lavallee, Ph.D., Soil Scientist

This CO₂ release is considered biogenic (happens through natural biological systems), not anthropogenic (people-made), and is not included in the calculations of greenhouse gas (GHG) emissions that drive global warming and climate change.

The three primary GHGs are:

Carbon dioxide (CO₂) — 300-1,000 year atmospheric lifetime; 86% of total GHG emissions
Methane (CH₄) — 84X the global warming potential of CO₂; 12 year atmospheric lifetime; 7% of total GHG emissions
Nitrous oxide (NO₂) — 265X the global warming potential of CO₂; 100 year atmospheric lifetime; 6% of total GHG emissions

There are many factors that determine the potential for composting to generate methane and nitrous oxide, like the mix of materials being composted, temperature, moisture, pile size and configuration, and aeration. Compost piles and windrows that are waterlogged and low in oxygen (anaerobic) are more likely to generate these GHGs. Composting is “climate-friendly” when it’s done in the presence of air (aerobic). Home and community composters turn piles by hand to keep them aerated and large-scale composting facilities use mechanical turners and force air into windrows with blowers. Well-managed composting at any scale releases very little methane or nitrous oxide into the atmosphere.

Direct climate benefits of composting

Dumping food wastes and grass clippings in landfills generates large amounts of methane because the decomposition process is anaerobic. Landfills release about 17% of total U.S. anthropogenic methane emissions and food waste makes up 24% of landfill space. Burning organic wastes releases GHGs and toxins. Composting these organic wastes using best practices greatly reduces emissions.
Carbon sequestration: Compost continues to degrade after soil incorporation. Some of the carbon cycles through soil microorganisms and some is held tightly to clay particles, protected against decomposition, and becomes part of the long-term reserve of stored carbon.

Indirect climate benefits of composting

The mid-Atlantic climate is becoming wetter and warmer overall, punctuated by localized extreme weather events, like record-breaking rainfall and extreme drought and heat. Intense storms can cause soils and nutrients to wash away and warmer temperatures cause more rapid organic matter decomposition and turnover, especially if soils are tilled and uncovered.

Adding compost to soils makes them more resilient by:

Holding more water in the soil during periods of drought and extreme heat
Reducing erosion (washing away of soil during extreme rainfall) and nutrient run-off) due to improved soil structure (larger, more stable aggregates or crumbs)
Improving plant growth, by slow release of plant-available nutrients
Reducing the need for synthetic nitrogen fertilizers which require natural gas for their production
Reducing the need for potassium and phosphorous fertilizers (derived from mined mineral deposits that are dwindling worldwide)
Binding and degrading toxic metals and pollutants
Substituting compost for peat products can help reduce the release of CO₂ from commercial peat extraction from wetlands

illustration of how compost combats climate change - increases water holding capacity - sequesters carbon in soil — Poster by the Institute for Local Self-Reliance

Home composting

Managing and recycling as much yard waste as possible on-site is often the most climate-friendly approach because it reduces GHG emissions from transporting and processing or landfilling organic waste. You can do this by recycling grass clipping (“mow ‘em high and let ‘em lie”), mulch-mowing tree leaves and leaving them in place, or using them as mulch, composting yard and garden waste, and burying kitchen scraps. These practices help to recycle nutrients on-site and increase soil organic matter. Selecting or building a non-plastic composter can also help reduce GHG emissions.

Municipal/commercial composting

This is the next best option for organic wastes that cannot be managed on-site. Commercial and municipal composting operations do create GHG emissions from the trucks and equipment, powered by fossil fuels, that are used to collect, transport, and process organic waste and compost. The closer the source of organic waste to the facility the lower the emissions and the greater the benefits. On balance, composting on a large scale can also help mitigate climate change.

illustration showing that the carbon sequestration benefits of municipal composting outweigh the greenhouse gases generated by transportation, storage, and processing compost

To summarize: aerobic composting reduces GHG emissions compared to the landfilling and incineration of organic wastes. The resulting compost sequesters carbon when mixed into soils and improves soil health and resiliency. Composting at home and in your community is the most climate-friendly approach but commercial and municipal composting is another important tool that helps mitigate climate change.

References

Silver, W. L., Vergara, S. E., & Mayer, A. (2018). Carbon sequestration and greenhouse gas mitigation potential of composting and soil amendments on California’s rangelands. California Natural Resources Agency, 62.
Linzner, R., & Mostbauer, P. (2005, October). Composting and its impact on climate change with regard to process engineering and compost application-a case study in Vienna. In Proceedings of Sardinia Tenth International landfill Symposium, Cagliari, CISA publisher.
UME- How to Make Compost at Home
Institute for Local Self-Reliance- Community Composting
U.S. Composting Council- Greenhouse Gases and the Role of Composting: A Primer for Compost Producers (includes some research studies on GHG emissions and composting facilities)
Maryland Department of the Environment- Organics Diversion and Composting
U.S. EPA- Overview of Greenhouse Gases

By Jon Traunfeld, Extension Specialist, University of Maryland Extension, Home & Garden Information Center. Read more posts by Jon.

Vegetable Problems Update

July 21, 2023August 4, 2023Maryland Grows2 Comments

Wildfire smoke

Persistent wildfire smoke is new for Maryland gardeners. Experts seem to agree that smoke and ash do not pose a health risk for garden produce. Smoke diffuses sunlight but will probably not significantly reduce the total amount of light for photosynthesis. We have not heard/seen any reports of gardeners picking up smoky flavors in harvested greens or other vegetables or fruits.

Wash all produce prior to eating it raw or cooking with it
Wear an N-95 quality mask when working outside on days when wildfire smoke worsens air quality
Hose off plants if a noticeable soot layer develops from prolonged, intense smoke

Wildfire smoke has been shown to boost the levels of ozone and other air pollutants which can injure plants. Watermelon, squash, pumpkin, beans, and potato are especially vulnerable to high ozone levels (above 75 ppb).

Drought and damaging storms

Wildfire smoke interfered with weather patterns and likely contributed to cooler and drier weather across much of the state.

Mid-May through June:

Lower average temperatures
75% of state in moderate drought on July 3rd
Slow start for warm-season crops

July:

High heat and humidity
Spotty rainfall
Insect and disease issues increasing

Maryland drought status map — The Maryland Department of the Environment announced a Drought Watch on July 10, encouraging voluntary reduction in residential water use.

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