The Science of Gardening
Linda Chalker-Scott is an Extension Specialist in Urban Horticulture and an Associate Professor of Horticulture at Washington State University. She received her Ph.D. in Horticulture from Oregon State University, focusing on environmental stress physiology of woody plants. She has worked at Buffalo State College and at the University of Washington, where she remains an affiliate faculty member. In addition to her academic credentials, she serves as a Certified Arborist with the International Society of Arboriculture and a Consulting Arborist with the American Society of Consulting Arborists.
Dr. Chalker-Scott has published in a number of peer-reviewed journals and written numerous science-based books for gardeners and landscape professionals. These include the award-winning The Informed Gardener; The Informed Gardener Blooms Again; and How Plants Work: The Science behind the Amazing Things Plants Do, which won awards from the American Horticultural Society and the National Association of County Agricultural Agents.
As an Extension Specialist, Dr. Chalker-Scott has an educational outreach program that includes homeowners, Master Gardeners, landscape professionals, restoration ecologists, and landscape architects. Since 2004, she has delivered more than 400 seminars, reaching more than 25,000 attendees. Dr. Chalker-Scott is also one of the founding Garden Professors, a group of university faculty who provide science-based information for gardeners through blogs and social media.
01: Garden Science: Weeding Out the Myths
How many of your horticultural practices are based on anecdotal evidence from your neighbor or grandmother, and how do you assess their validity? In the midst of an unregulated “Wild West” of gardening products and practices, you can learn to access science-based information to create your sustainable dream garden.
02: Site Analysis: Choosing the Right Spot
Many of us make our landscape choices based on plant aesthetics. Instead, learn to first identify your location’s topography, prevailing winds, hydrology, soil type, and other environmental factors. Then you’ll be able to choose a plant well-suited for the long term. And you’ll avoid season after season of frustration.
03: Soil Analysis: What Makes Soil Great?
Unless you live in a completely undeveloped area, chances are your home garden soil is not native. Learn what makes a “great” soil and how to determine your own approximate amounts of clay, silt, and sand; texture; nutrients; pH; and more—before you purchase that “must have” soil addition from the gardening store.
04: Living Soils: Bacteria and Fungi
Just as humans cannot grow without our supportive microbiome, neither can plants. Plant roots, bacterial sheathes, and long filaments of fungus all function together to support the plant’s growth, enhancing the uptake of water and nutrients and improving soil structure. But what happens to this crucial symbiosis when you add unnecessary fertilizers?
05: Plant Selection: Natives versus Non-Natives
Native plants are always a better home-garden choice than non-natives, right? We know they are best suited to thrive in the soils and ecosystems of the area, and will create the best wildlife habitat. But does garden science support those “truths”? You might be surprised to learn how introduced species can enhance your garden and landscape biodiversity.
06: Plant Selection: Function and Form
In addition to its aesthetic value, your landscaping can provide privacy, protect soils from erosion, moderate temperature, manage storm-water runoff, provide wildlife habitat, and more. Learn how to select the appropriate plants with respect to morphology, growth rates, and physiology to help achieve your specific goals for various locations on your property.
07: Plant Selection: Finding Quality Specimens
Half the battle of successful landscaping is starting with the healthiest specimens—not, as we sometimes prefer, the largest. Learn how to inspect nursery plants from the crown to the ground for evidence of quality and health, and how to estimate root health by checking for suckers on single-trunk trees, root flare, surface roots, and the “tippy test.”
08: Soil Preparation and Protection
“Don’t plant before you fertilize!” Chances are you’ve heard that admonishment more than once. But gardening science has revealed that many popular practices—including fertilizing every time you plant—are neither necessary nor sustainable. Learn about a more natural way to add organic material to your garden to protect soil structure and nourish your plants.
09: The Truth about Mulch
Learn about the wide variety of mulch types—from glass to wood to compost—and the science-based pros and cons of each. By considering your specific site conditions and personal aesthetics, you can blend a variety of mulches to transform a struggling landscape into one that’s healthier and more sustainable.
10: Planting for Survival
Current research supports the need to radically change the way we’ve been planting trees for the past half century. Although considered controversial by nursery professionals, learn why plant science supports the “old” method of bare-root planting. This technique can improve tree survival because a vigorous root system will better support a healthy crown.
11: Aftercare for New Plants
Once your new plant is in the ground, how should you take care of it? Learn the basics of watering, mulching, fertilizing, staking, and pruning newly transplanted trees or shrubs—and why this care might change in subsequent seasons when the plant is well established. Not sure if your newly planted tree is experiencing healthy root growth? Try the wiggle test.
12: Plant Nutrition: Evidence-Based Fertilizing
The goal of fertilizing is to match your soil and plant needs—micro- and macronutrients, and other chemical requirements—with the appropriate sources of nutrition. By understanding your specific soil test results, you can determine which nutrients are deficient, which might already be present in toxic quantities, and whether or not to buy organic.
13: The Art and Science of Pruning
Have you ever seen a tree cut painted with tar or another sealant? Or seen a crown chopped completely bare? Both are common practices that we now know are harmful to the plant. Using applied plant physiology and science-based guidelines, learn the best timing and methods for pruning that will lead to healthy tree growth for the long term.
14: Creating Safe Food Gardens
While it seems intuitive that vegetables grown in your home garden will be safer and healthier than those purchased at the supermarket, that could be a dangerous assumption. Does your garden soil contain elements of concern, especially cadmium or lead? If so, learn how to best respond—whether in plant choices or creative garden design.
15: Water-Wise Landscaping
Learn how to reduce water use and protect water quality using knowledge of plant biochemistry, transpiration, and photosynthesis. Designing garden modifications, choosing appropriate plants based on morphology and color, and incorporating shading and mulch to reduce evaporation are just some of the water-wise techniques that will help conserve water.
16: Diagnosing Diseases and Disasters
The most common cause of death for home garden plants is poor horticultural practices, not disease or pests. With this step-by-step guide to diagnosing plant problems, you’ll learn how to appropriately remedy any problem—and when the plant will heal on its own. You’ll also be able to identify the warning signs of future problems, so you can treat the issue before it’s too late.
17: Gardening CSI: Case Studies
Take a virtual field trip to see examples of unhealthy plants and learn how to diagnose their problems based on the science of plant physiology. You’ll see tree girdling, plants that become smaller over time instead of larger, scorched shrubs, and more. Once you understand the physiology behind these problems, you’ll be better able to diagnose and treat any of your garden’s plants that might be failing.
18: Integrated Pest Management
There is no lack of chemicals to get rid of the pests in your garden—whether that pest is a plant, insect, or other organism. But for long-term health, integrated pest management provides a better, systematic, science-based approach with a minimum of chemical inputs. With IPM, the goal isn’t to eradicate the pests, but to identify your tolerance level for their presence and implement appropriate management techniques.
19: Understanding Pesticides
Yes, there can be an appropriate time for judicious use of chemical pesticides in your garden—as a last resort to solve specific problems. Learn why you should always stick with those approved by the EPA and your state department of agriculture, and never use the home remedies promoted on the Internet or in non-science-based books. Are organics always safer ecologically than synthetics? You’ll be surprised.
20: What to Do about Weeds
If you have a garden in the U.S., chances are you’re familiar with the damage caused by English ivy, kudzu, purple loosestrife, and/or the tamarisk tree. Each of these hardy plants can quickly create a monoculture, driving out other plant species and limiting the availability of diverse animal habitat. Learn the best science-based mechanisms to control these plants.
21: What to Do about Insects
Before you resort to chemical sprays—which can kill all insects, not just the pests you’re targeting—learn how to manage insects by increasing plant diversity, establishing “trap” plants, and using repellents and tools including your basic garden hose. But before you do anything, know your “enemy.” Understanding the life cycle and reproductive physiology of the insect will help you make the most effective management choices.
22: What to Do about Herbivores
You could spend a lot of money trying to keep slugs, rats, moles, rabbits, squirrels, deer, and other herbivores out of your garden. But most of those purchases would have little, if any, value, especially if feeding pressure is high in the surrounding habitat. Learn about the few options that are both safe and effective. And remember, “man’s best friend” might be your garden’s best friend, too.
23: Tackling Garden Myths and Misinformation
If you can’t trust the Internet home remedy or the local gardening salesperson, whom can you trust? Make science-based gardening decisions by assessing the credibility, relevance, accuracy, and purpose of the information you read. Learn to understand the significant role played by peer review, the crucial difference between correlation and causation, and how to watch out for over-extrapolation and misapplied science.
24: Applied Garden Science: Success Stories
Two specific transformation stories—a wetlands restoration and a home garden project—reflect the benefit of science-based planning by considering soils, temperature, sunlight, moisture, water table, and likely pests. Learn how to become a citizen scientist and contribute to the field, not by looking for the easy way out, but by asking the hard questions and knowing how to assess the strength of the answers.