Region 06 · North America · Csb
Horticulture in North America: Pacific Northwest
Wet winters and dry summers create a Mediterranean rhythm in a cool climate; conifers, moss and woodland perennials do the heavy lifting. The dry summer is the design constraint, not the rain.
ClimateWarm-summer Mediterranean (Csb)
USDA zones7–9
Growing seasonMarch to October
RainfallWet winter, dry summer
SoilsAcidic, high organic matter, glacial
Frost riskGrowthRainfall
The climate, read as a season
Peak growth falls in Apr, May, Jun; dormancy in no true dormancy. Hard frost is confined to Jan, Feb, and the driest months are Jun, Jul, Aug, Sep. Those three patterns decide the planting calendar more than the annual average temperature.
| Season | Conditions | What it means |
|---|---|---|
| Spring Mar · Apr · May | Peak growth drier spell · light frost | Plant, but keep protection for tender crops. |
| Summer Jun · Jul · Aug | Active growth dry season · frost-free | Irrigate and mulch; avoid new planting without water. |
| Autumn Sep · Oct · Nov | Active growth drier spell · frost-free | Maintain, harvest and prepare the next season. |
| Winter Jan · Feb · Dec | Slow growth wettest quarter · hard frost | Maintain, harvest and prepare the next season. |
What the climate demands
- Summer drought is real even in a rainforest reputation: new plantings need water for two summers.
- Moss, liverwort and poor drainage dominate shady lawns; aeration and shade management come first.
- Acid soils and cool nights suit rhododendron and conifer, not heat-loving vegetables without a warm microclimate.
Signature flora
| Plant | Role | Why it is used here |
|---|---|---|
| Douglas fir Pseudotsuga menziesii | ConiferTreeNative | The defining conifer; needs space and light. |
| Western redcedar Thuja plicata | ConiferTreeHedge | Hedge and timber tree; needs moisture. |
| Western hemlock Tsuga heterophylla | ConiferTreeNative | Shade tolerant; deep shade and rain. |
| Vine maple Acer circinatum | TreeNative | Understorey; orange fall colour. |
| Japanese maple Acer palmatum | Tree | Part shade; wind protection. |
| Rhododendron Rhododendron | ShrubNative | Acid soil; lacebug and root weevil. |
| Camellia Camellia | ShrubCut flower | Sheltered shade; early flowers. |
| Oregon grape Mahonia | ShrubNative | Dry shade; yellow winter flowers. |
| Salal Gaultheria shallon | GroundcoverNative | Acid woodland; edible berries. |
| Hellebore Helleborus | Perennial | Winter flowers in dry shade. |
| Japanese forest grass Hakonechloa macra | GrassPerennial | Shade; moist but drained soil. |
| Sword fern Polystichum munitum | PerennialNative | Dry shade under conifers. |
| Bleeding heart Dicentra | Perennial | Spring ephemeral; summer dormancy. |
| Hydrangea Hydrangea | ShrubCut flower | Moisture and afternoon shade. |
| Dahlia Dahlia | Cut flowerBulb | Lift tubers in cold gardens; stake tall cultivars. |
| Garden rose Rosa | ShrubCut flower | Blackspot pressure in wet springs. |
| California lilac Ceanothus | ShrubNativeWater-wise | Dry sun; fast; short-lived. |
| Manzanita Arctostaphylos | ShrubNativeWater-wise | Sharp drainage; no summer water. |
| Blueberry Vaccinium | BerryNative | Acid soil; two cultivars. |
| Raspberry Rubus | BerryEasy to propagate | Moist soil; trellis. |
| Tomato Solanum lycopersicum | VegetableAnnual | Needs a warm wall or greenhouse. |
| Kale Brassica oleracea | Vegetable | Cool-season; excellent autumn crop. |
| Pea Pisum sativum | Vegetable | Sow February–April; cool season. |
| Onion Allium cepa | VegetableRoot crop | Sets and transplants; cure before storage. |
| Apple Malus domestica | FruitTree | Scab pressure in wet springs. |
| Hop Humulus lupulus | Vine | Fast screen; dies back in winter. |
| Kentucky bluegrass Poa pratensis | Turf | Lawn needs summer irrigation. |
| Red fescue Festuca rubra | Turf | Low-input lawn; shade tolerant. |
| Slough sedge Carex obnupta | GrassWetlandNative | Rain garden and wet swale. |
| Red-osier dogwood Cornus sericea | ShrubNativeWetland | Wet tolerant; winter stems. |
The eight disciplines here
| Discipline | What it looks like here | Taxa | Read |
|---|---|---|---|
| Garden Design 01 | Palette and practice for garden design in this climate. | 20 | Discipline guide |
| Floriculture 02 | Palette and practice for floriculture in this climate. | 5 | Discipline guide |
| Vegetables & Herbs 03 | Palette and practice for vegetables & herbs in this climate. | 4 | Discipline guide |
| Fruit & Viticulture 04 | Palette and practice for fruit & viticulture in this climate. | 4 | Discipline guide |
| Arboriculture 05 | Palette and practice for arboriculture in this climate. | 6 | Discipline guide |
| Turfgrass 06 | Palette and practice for turfgrass in this climate. | 2 | Discipline guide |
| Nursery & Propagation 07 | Palette and practice for nursery & propagation in this climate. | 16 | Discipline guide |
| Water-wise & Restoration 08 | Palette and practice for water-wise & restoration in this climate. | 14 | Discipline guide |
Professional bodies and standards
International Society of Arboriculture (ISA) · Washington State University Extension
Design idiom
Japanese garden, woodland, rain garden.
Sources
Other regions
California & Southwest · US Southeast · Tropical Latin America · Andes & South America · all 16 regions