Washington has temperate rainforest, sagebrush steppe, and alpine meadows within the same state, so gardening advice that works in one region may not work in another. This episode explains how Level III ecoregions, a framework developed by the EPA, can help you understand the conditions in your own garden.

We start with what a Level III ecoregion is and how it differs from a USDA hardiness zone. Then we cover eight Washington regions:

• Coast Range
• Puget Lowland
• Cascades
• North Cascades
• Eastern Cascades Slopes and Foothills
• Columbia Plateau
• Blue Mountains
• Northern Rockies

For each region, we look at the climate, the soils, the native plants that grow there, and what those conditions mean for your garden.

Resources mentioned in this episode, along with a full transcript, can be found on our website.

In this episode of The Evergreen Thumb, Erin Hoover talks with Tim Kohlhoff about the role trees play in creating healthier, more livable communities. They explore why urban tree canopies matter, the challenges communities face in protecting them, and how thoughtful tree planting can help shape the future of our neighborhoods.

Resources mentioned in this episode, along with a full transcript, can be found on our website.

In this episode of The Evergreen Thumb, Erin Hoover covers everything you need to know about growing garlic in Washington state. She explains the difference between hardneck and softneck garlic, shares her own growing experience, and touches on elephant garlic as well.

Erin walks through site selection, sourcing seed garlic, regional planting timing, spacing methods, and mulching for winter protection. She covers scape removal in early summer and when to stop watering before harvest, then closes with guidance on curing garlic for maximum storage life and an overview of common garlic pests and diseases, including prevention tips like crop rotation and separating garlic from onions.

Resources mentioned in this episode, along with a full transcript, can be found on our website.

What does it take to protect important crops from harmful plant pathogens? In this episode of The Evergreen Thumb, we explore the work of the Clean Plant Center Northwest at Washington State University with its director, Sudarsana "Sud" Poojari.

Sud explains what clean plant material means, why it matters to U.S. agriculture, and how plant material moves through testing and treatment before being released as clean foundation material. We also explore how that foundation material is used by commercial growers and nurseries to help produce healthy fruit trees, grapevines, and hop plants.

In this episode:

• The mission and role of the Clean Plant Center Northwest
• What "clean plant material" means and why it matters
• The journey of plant material through testing and treatment
• How clean foundation material supports fruit trees, grapes, and hops
• How commercial growers and nurseries use clean plant material
• What CPCNW's work means for home gardeners
• The future of clean plant programs

Resources mentioned in this episode, along with a full transcript, can be found on our website.

Fall may feel like the end of the gardening season, but for many spring-flowering plants, it's just the beginning.

In this episode of The Evergreen Thumb, Erin explores fall planting in Washington, with a focus on spring-flowering bulbs and other geophytes. We'll look at why fall is the right time to plant many of these plants, how soil temperature affects planting timing, and what Washington gardeners should consider when deciding when to get their bulbs in the ground.

We'll talk about familiar garden favorites such as daffodils, tulips, and hyacinths, along with some less familiar native geophytes, including camas and fawn lilies for seasonal interest and to support regional biodiversity.

Cover crops can protect and improve garden soil during the time of year when our gardens are resting. In this episode, Erin talks with Twinflower Wilkie, a WSU Extension Master Gardener in Ferry County, about how cover crops help retain moisture, protect soil from erosion, cycle nutrients, and build healthier soil.

Twinflower also shares why cover crops can benefit pollinators and other beneficial wildlife, and why allowing your garden to go a little wild can be good for the garden and the creatures that depend on it. They discuss choosing and using cover crops in the home garden and simple ways gardeners can get started.

For gardeners in Washington's dry eastern climate and beyond, cover crops offer a practical way to keep soil protected and productive while creating a more welcoming garden for wildlife.

Resources mentioned in this episode, along with a full transcript, can be found on our website.

Every gardener has encountered advice that promises amazing results, from family traditions passed down through generations to the latest trend making the rounds on social media. How do you know what to trust?

In this episode, Erin talks with Bryce Battisti about what "research-based" really means and why it is a core part of the WSU Extension Master Gardener Program. Bryce shares his own journey from embracing popular gardening ideas to appreciating the value of research in helping gardeners make informed decisions.

Together, they explore how gardening recommendations are developed, why scientific understanding changes as new discoveries are made, and why local research is especially valuable for Washington gardeners. They also discuss practical ways to evaluate gardening advice, identify reliable sources, and avoid wasting time and money on untested practices.

Resources mentioned in this episode, along with a full transcript, can be found on our website.

In this episode of The Evergreen Thumb, Erin Hoover chats with Julie Banken, a Master Gardener with a background in entomology, about creating pollinator-friendly gardens by rethinking traditional fall cleanup practices. Julie shares her passion for gardening with insects in mind, explaining how leaving leaves, stems, and other natural debris provides essential winter habitat for a wide variety of pollinators and beneficial insects. She encourages gardeners to view their yards as crucial parts of the ecosystem, highlights the importance of native plants, and offers practical advice for supporting insect life cycles—like leaving leaf mulch and standing stems through winter and only tidying up the next year. By making simple intentional changes, gardeners can help sustain the pollinators and insects that depend on them, making a positive impact right in their home gardens.