Spokane Landscape Architecture: Climate, Soil, and Site Considerations
By Joshua Tripp, Landscape Architect, ASLA Last updated: August 2026
People move to Spokane expecting Pacific Northwest green and get a semi-arid steppe climate sitting on top of basalt bedrock instead. That mismatch between expectation and reality is the single biggest reason landscape projects in this city go sideways — homeowners design around a Seattle mental model and then fight their own site for three years. From our Spokane office at 125 S Stevens St, this is the site conversation we have before we talk about a single plant.
Spokane Isn't "Generic PNW" — and Treating It That Way Is the First Mistake
West-side Washington landscaping content — the glossy hydrangea-and-fern imagery most homeowners pull up on Pinterest — assumes 35+ inches of annual rainfall and mild winters. Spokane gets roughly 17 inches of precipitation a year, sits in a high-desert steppe climate, and swings from summer highs in the 90s to hard winter cold snaps. Under the 2023 USDA Plant Hardiness Zone Map, most of the city falls in Zone 6b to 7a — a meaningfully warmer classification than the 2012 map, but still a world away from the moderating marine influence that makes Western Washington's plant palette work.
Our opinion, stated plainly: a landscape plan built from West Side inspiration photos will underperform in Spokane regardless of budget. The plants, the irrigation strategy, and the soil prep all have to be built for an inland steppe climate with basalt geology underneath — not adapted from a coastal template after the fact.
The Basalt Problem: Why Spokane Soil Fights You
Spokane sits on the Columbia River Basalt Group, the massive volcanic flows that also underlie the Palouse. In much of the city — the South Hill, Five Mile Prairie, and the rimrock areas above the Spokane River — that basalt sits close enough to the surface that homeowners hit rock within a foot or two of grade. Where the basalt is capped by loess (the fine windblown silt typical of the Latah Formation and Palouse country), you get better depth, but drainage and compaction problems show up fast in the Latah and related soil series common to low terraces along the region's drainageways.
Practically, that means three things we address on nearly every Spokane residential project:
Excavation reality-testing before design. A planting plan drawn without a test pit or two is a plan that gets redrawn on-site. We flag likely rock depth by sub-area before finalizing bed layouts, not after the excavator hits basalt.
Amended planting pockets, not amended yards. Trying to till 8 inches of compost into basalt-adjacent soil across an entire lot is expensive and often unnecessary. Targeted, well-built planting pockets for trees and major shrubs perform better than a blanket soil replacement, in our experience.
Drainage design that assumes rock, not clay. Spokane's basalt and loess combination drains very differently than the clay soils most generic landscape guidance is written for. Grading and drainage plans that don't account for shallow bedrock create standing water and root problems within a season or two — and if grading changes affect structural drainage near a foundation, that's a coordination point we handle directly with the builder.
Spokane Sub-Area | Typical Site Condition | Design Implication |
South Hill / rimrock areas | Shallow basalt, thin soil, rock outcrops | Planting pockets over full-bed tilling; retaining structures common |
Five Mile Prairie | Basalt near-surface, exposed, windy | Wind-tolerant plant selection; irrigation sized for exposure |
River valley / lower terraces | Deeper loess-derived (Latah-series) soils | Better planting depth; drainage and compaction still a factor |
Newer suburban plats (Spokane Valley, north Spokane) | Variable — often construction-compacted subsoil over native basalt/loess | Soil decompaction and structured planting pockets before install |
Climate: Design for the Swing, Not the Average
Spokane's inland steppe climate means bigger temperature swings than coastal PNW cities — hot, dry summers; cold snaps that can hit well below the "average" winter low; and a shorter, more variable shoulder season. A few implications that matter more here than on the coast:
Irrigation is not optional. Unlike Western Washington, where established plantings often survive on rainfall alone, Spokane's dry summers mean irrigation planning is a core design decision, not an add-on.
Snow load and freeze-thaw affect hardscape, not just plants. Retaining walls, paver bases, and drainage systems need to be detailed for freeze-thaw cycling that Western Washington designs rarely account for.
Microclimate matters more than the zone map. WSU Extension's own guidance is clear that hardiness zone is a starting point, not a guarantee — south-facing basalt outcrops bake hotter and drier than a shaded northern exposure a quarter-mile away. We site-assess microclimate on every project rather than defaulting to the zone average.
Frequently Asked Questions
Is Spokane really that different from the rest of "Pacific Northwest" landscaping advice? Yes. Spokane's semi-arid steppe climate, basalt geology, and roughly 17 inches of annual precipitation put it much closer to an inland dry climate than to the marine-influenced conditions west of the Cascades that most generic PNW landscaping content assumes.
Do I need a soil test before starting a landscape project in Spokane? We strongly recommend it, especially near the South Hill, Five Mile Prairie, or any lot with visible rock outcrops. A test pit or two during design avoids redesigning beds mid-excavation when basalt shows up sooner than expected.
What USDA hardiness zone is Spokane in? Most of the city falls in Zone 6b to 7a under the 2023 USDA Plant Hardiness Zone Map, a warmer classification than the older 2012 map — but zone alone doesn't account for Spokane's microclimates or its basalt-driven drainage differences.
Can I just till compost into my whole yard to fix basalt-adjacent soil? You can, but it's often not the most effective use of budget. We typically recommend well-built planting pockets for trees and major shrubs rather than blanket soil replacement across an entire property.
Does snow load actually affect landscape design, not just the house? Yes — retaining walls, paved surfaces, and drainage systems in Spokane need to be detailed for freeze-thaw cycling and snow loading, which is a different structural conversation than what's typical in milder coastal climates.
Should I choose plants based only on the hardiness zone map? No. WSU Extension's own guidance treats the hardiness zone as a starting reference, not the deciding factor — sun exposure, wind, slope, and basalt proximity all shift what actually thrives on a given Spokane lot.
Site-Specific Design, From a Firm Based Here
We've built our Spokane practice around this exact gap — a citywide climate and geology that most landscaping content simply doesn't address correctly. If you're planning a residential or commercial landscape project in Spokane, reach out to talk through your specific site, or explore our related guide to Coeur d'Alene mountain home landscaping if your property sits closer to the Idaho panhandle. For projects involving new construction or major grading, coordinating early with your builder — as we regularly do with MVC Sandpoint on North Idaho sites — keeps the site work and the landscape design working together instead of against each other.
Image: photo by Jeffrey Eisen on Pexels
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