The Evergreen Thumb

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.