Linda Chalker-Scott

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• PhD
• Extension Urban Horticulturist at Washington State University

Companion planting is a legitimate horticultural practice that uses ecological principles of beneficial plant relationships to enhance establishment and survival of desired plants. The concept has been mythicized by nonscientists who have assigned zodiac, occult, or other pseudoscientific qualities to plants, which creates confusion for home garden...

Despite global concerns regarding climate change, one thing remains constant: homeowners want gardens and landscapes that serve them functionally and aesthetically. The strong affinity homeowners have for their land can lead to excessive use of water and fertilizer. This literature review explores the relationships between homeowners and their resi...

Extension personnel and Master Gardener volunteers have identified adult mantids brought in by Washington residents to county and state diagnostic clinics. This diagnosis is rather easy as the mature insect is green or brown, measures 2 to nearly 3.5 inches long, and has raptorial forelegs armed with spines and held in the manner of hands folded in...

Residential gardeners often use rain barrels to collect rainwater from roofs as a supplement to summer irrigation. Rainwater is a natural and unchlorinated water source for aquatic plants and animals. However, rooftop runoff can be contaminated by chemical and biological pollutants from atmospheric deposition, bird droppings, and the roofing materi...

Lady beetles—also incorrectly called lady “bugs” (bugs and beetles are not closely related)—are a natural and popular biocontrol agent for aphids in home gardens, landscapes, and other urban environments (Egerer et al. 2017; Lowenstein et al. 2017). Many gardeners purchase these insects online or at nurseries and garden centers for release on their...

The current trajectory of climate change suggests that summer temperatures will rise, and drought conditions worsen in many parts of the world. Mulches can reduce soil water loss in gardens and landscapes. Not all mulches are created equal, however, and some mulches can damage both soil and plant health. This literature review will focus on arboris...

Homeowners and landscape professionals alike are interested in proper pruning techniques for their trees and shrubs. Hundreds of popular books and online resources present confusing and conflicting pruning instructions, many of which are not science-based. In this literature review, we explain how woody plant physiology predicts tree and shrub resp...

Home gardening is increasingly popular, particularly during a global pandemic when many people are confined to home and are spending more time outside. Novice and experienced gardeners alike are likely to access agricultural production information that is not necessarily relevant to their home gardens or landscapes. Specifically, there are soil fer...

Some homeowners are lucky enough to have streams, ponds, or other bodies of water on their property. The transitional area between water and land requires careful management to protect the health of both ecosystems. This publication will help home gardeners and other private landowners to create an aesthetically pleasing landscape without damaging...

Soils found in home gardens and public landscapes usually bear little resemblance to the original soil. Native soils are formed through centuries of interactions between climatic factors, local environmental factors, and the biological components of the soil. In contrast, soils found in developed areas (called “urban” soils throughout this article)...

Processed seaweeds, especially kelps, are heavily marketed to gardeners as biostimulants, fertilizers, soil conditioners, disease suppressants, and environmental stress reducers. This publication reviews the published research on seaweed products regarding their effectiveness in home gardens and landscapes. It also discusses the ecological and envi...

Once a popular commercial method of growing commercial crops, straw bale gardening is experiencing a resurgence among home gardeners. This publication addresses the scientific research behind straw bale gardening and explains the evidence-based benefits and drawbacks for gardeners creating straw bale gardens at home.

Mulching is a common soil management technique used in agricultural, nursery, and landscape settings. Despite multiple benefits, such as reducing weeds and evaporation, some mulches can also hinder gas exchange across the soil-atmosphere interface, and thus may have negative impacts on plant growth. The objective of this study was to determine to w...

Horticultural myths, found extensively in print and online resources, are passed along by uninformed gardeners, nursery staff, and landscape professionals. Occasionally myths are so compelling that they make their way into Extension publications, used by Master Gardeners as educational resources. In this article we deconstruct seven widespread gard...

Mycorrhizae are symbiotic associations between many plants and the beneficial fungi that colonize their roots. Gardeners are often unaware of these relationships and may inadvertently injure or kill the beneficial fungi through common gardening activities. This publication will help home gardeners understand the benefits of mycorrhizae and explain...

The Garden Team at Washington State University is a transdisciplinary, geographically dispersed group of faculty and staff. As with many such teams, member retention requires effort, as busy individuals may not see the overall benefits of active team membership. Ripple effect mapping is a strategy that can illustrate the tangible and often unexpect...

The Garden Team at Washington State University is a transdisciplinary group of faculty, staff, and students with expertise in applied plant and soil sciences and an interest in Extension education. The team's primary mission is to create current, relevant, and peer-reviewed materials as Extension publications for home gardeners. The average yearly...

Knowledge of the scientific method leads to scientifically literate citizens who can read science articles and evaluate the quality of the information presented; it allows a person to distinguish science from pseudoscience and can help avoid wasting time, money, and resources on poor ideas or, worse, scams. The scientific method is also useful for...

Increasingly, homeowner associations and municipalities are requiring a certain percentage of native trees and shrubs as part of any new landscape installation. These native species mandates make numerous claims as to the superiority of native plants over introduced species, including their ability to enhance ecosystem biodiversity. In contrast, no...

Biodynamics is a form of organic agriculture first described in the 1920s by Rudolph Steiner, and practitioners can become certified biodynamic farmers by following specified practices. What distinguishes biodynamic from organic certification is the required use of nine preparations thought to improve soils and increase crop yields. This literature...

In July 2009 four faculty members from four different institutions created a blog to educate consumers and professionals about plant-related issues. Online resources were used to measure the number of times that the blog was viewed and its impacts. The blog averages about 200 views a day, and 80% of those responding to a survey could name specific...

Best management practices (BMPs) for urban landscapes are often based on production agriculture methods rather than current research in the field of urban horticulture. In particular, the overuse of organic amendments in landscape situations results in soil subsidence, poor plant health, and nutrient overload, which in turn can impact aquatic syste...

Best management practices (BMPs) for urban landscapes, including school grounds and college campuses, are often based on production agriculture methods rather than current research in the field of urban horticulture. In particular, the overuse of organic amendments in landscape situations results in soil subsidence, poor plant health, and nutrient...

Educators recognize the ecological, economic, and social components of environmental sustainability. For community-based programs, there is another sustainability trio that, if neglected, will lead to a decline in program quality and function. To be sustainable over the long term, community-based programs must have superior educational quality, cle...

Mulches provide aesthetic, economic and environmental benefits to urban landscapes. Mulching is especially useful in the establishment of trees in landscapes that receive minimal care, such as restoration sites. In general, mulches improve soil health, creating healthy populations of plants and associated animals. These biodiverse, stable landscape...

The Master Gardener (MG) program, found throughout the United States and Canada, originated in Washington State to provide high-quality, research-based, educational programming to the gardening public. Washington State MGs are trained by Washington State University (WSU) faculty and other specialists in applied plant and soil sciences. After comple...

Previously, we have shown a cold-hardening response in Rhododendron 'English Roseum' exposed to elevated ultraviolet-B radiation (UV-B, 280-320 nm) under growth chamber conditions. We have conducted the present study under field conditions to provide for a higher ratio of photosynthetically active radiation to UV-B (PAR:UV-B) than is possible in th...

Humans have introduced many non-native plants into urbanizing landscapes. In numerous cases, the dispersal and establishment of non-native plants are facilitated by birds. We have reviewed documented relationships between birds and non-native plants with specific attention to the urbanizing environment. Birds consume fruits and disperse seeds of no...

The ability to avoid or tolerate UVB radiation (290-320 nm) probably reduces the quality of phytoplankton as food for zooplankton. Ultraviolet avoidance forces motile algae lower in the water column, reducing net primary productivity. Production of UV-absorbing compounds as a tolerance mechanism takes carbon and energy away from cell growth; these...

Anthocyanins are water-soluble pigments found in all plant tissues throughout the plant kingdom. Our under- standing of anthocyanin biosynthesis and its molecular control has greatly improved in the last decade. The adaptive advantages of anthocyanins, especially in non- reproductive tissues, is much less clear. Anthocyanins of- ten appear transien...

It has been previously shown that dormant, cold-hardy floral buds of Azalea possess layers of highly lignified and suberized cells below the bud axis and beneath each bud scale. Two species of deciduous Azalea were analyzed bi-weekly using differental thermal analysis (DTA) throughout their dormant season to determine the development of cold hardin...

Abstract The ability to avoid or tolerate UVB radiation (290–320 nm) probably reduces the quality of phytoplankton as food for zooplankton. Ultraviolet avoidance forces motile algae lower in the water column, reducing net primary productivity. Production of UV-absorbing compounds as a tolerance mechanism takes carbon and energy away from cell growt...

The marine harpacticoid copepod, Tigriopus californicus (Baker), is a successful colonizer of supralittoral splash pools from Torch Bay, Alaska, to Baja California, Mexico. As these pools are subject to abundant amounts of direct solar radiation, it was of interest to determine the sensitivity of T. californicus to ultraviolet-B (UV-B, 290 to 320 n...

The change in the cold hardiness of Rhododendron (cv. `English Roseum' following chronic exposure to ultraviolet-B radiation (280-320 nm) was studied. Leaf disks removed from ultraviolet-B exposed plants exhibited a greater tolerance to freezing temperatures than plants which received no ultraviolet-B exposure. Visual browning and percent phenolic...

The change in the cold hardiness of Rhododendron (cv. English Roseum) following chronic exposure to ultraviolet-B (UV-B) radiation (280–320 nm) was studied. Leaf disks removed from UV-B-exposed plants exbibited a greater tolerance to freezing temperatures than plants that received no UV-B exposure. Visual browning and percent phenolic leakage indic...

Leaf disks of Rhododendron cv. `English Roseum' were vacuum infiltrated with buffered solutions of L- or D-phenylalanine. Controls were infiltrated with buffer. Following a 24 hour period under lights (23°C, 16 hr light: 8 hr dark), the disks were cold shocked at 0°C for one hour, then held under the same light regime for three days. Disks were the...

Ice nucleating barriers of undetermined composition are known to occur in floral buds of several cold hardy species, including Azalea . Fluorescence microscopy indicated the presence of phenolic-nch areas within hardy Azalea flower buds, which could be ice barriers. Hardy buds were subjected to a sublethal heat stress of 45 °C for 2 h to disrupt ba...

Hardy buds of Azalea spp. were subjected to a sublethal heat stress of 45°C for 2 hours. Two hours after treatment the low temperature exotherms (LTE's) of the primordia were determined by differential thermal analysis (DTA). The LTE's of buds exposed to heat stress were either fewer in number and/or occurred at higher temperatures than in controls...

Rhododendron leaf disks ( Rhododendron L., cv. Jean Marie de Montague) release water-soluble phenolic compounds when subjected to lethal freezing stress. Following low-temperature exposure, the levels of phenolic compounds leached from the disks are assessed by spectrophotometric measurement (260 nm). The increase in phenolics is highly correlated...

The functions and localization of condensed tannins and their catechin precursors, together with the microscopic techniques for observing them, are discussed in this chapter. Unlike previous reviews,1 this chapter does not focus on heartwood formation, but rather on the presence of condensed tannins in living tissues. The occurrence and role of con...

Current trends in chromatographic isolation and analyses of proanthocyanidins are reviewed. Preparative isolations by low pressure column chromatography can be carried out using a variety of gel types. Often, repeated separations are required to obtain pure compounds, and it has been found advantageous to alternate each separation with a different...