Region 07 · North America · Csa / BWh / BSh
Horticulture in North America: California & the Southwest
Two climates meet: winter-rain Mediterranean California and the summer-monsoon desert Southwest. Both are water-limited, fire-shaped and alkaline in places, so the palette is built on drought and heat tolerance first.
ClimateMediterranean and arid (Csa / BWh / BSh)
USDA zones5–11
Growing seasonOctober to May (CA); July–September monsoon (SW)
RainfallWinter rain in California; summer monsoon in the Southwest
SoilsAlkaline, sandy, low organic matter
Frost riskGrowthRainfall
The climate, read as a season
Peak growth falls in Mar, Apr, May, Oct; dormancy in no true dormancy. Hard frost is confined to no hard-frost months, and the driest months are Apr, May, Jun, Jul, Aug, Sep, Oct. Those three patterns decide the planting calendar more than the annual average temperature.
| Season | Conditions | What it means |
|---|---|---|
| Spring Mar · Apr · May | Peak growth dry season · frost-free | The main planting and sowing window. |
| Summer Jun · Jul · Aug | Slow growth dry season · frost-free | Irrigate and mulch; avoid new planting without water. |
| Autumn Sep · Oct · Nov | Active growth dry season · frost-free | Irrigate and mulch; avoid new planting without water. |
| Winter Jan · Feb · Dec | Slow growth steady rain · light frost | Maintain, harvest and prepare the next season. |
What the climate demands
- Water is the binding constraint: irrigation budgets, runoff rules and plant choice are all one decision.
- Fire is a design parameter; keep defensible space and avoid high-resin, high-fuel plants near structures.
- Alkaline, salty soils and treated water cause chlorosis; choose tolerant species or amend locally.
Signature flora
| Plant | Role | Why it is used here |
|---|---|---|
| Coast live oak Quercus agrifolia | TreeNativeWater-wise | Evergreen oak; no summer water once established. |
| Western sycamore Platanus racemosa | TreeNativeWetland | Riparian; fast and large. |
| California bay Umbellularia californica | TreeNative | Shade and screen; fragrant leaves. |
| Ponderosa pine Pinus ponderosa | ConiferTreeNative | Montane; needs space and fire clearance. |
| Manzanita Arctostaphylos | ShrubNativeWater-wise | Sharp drainage; no summer water. |
| California lilac Ceanothus | ShrubNativeWater-wise | Fast, blue, short-lived; dry slopes. |
| Cleveland sage Salvia clevelandii | ShrubNativeWater-wise | Fragrant foliage for arrangements; dry sun. |
| Flannelbush Fremontodendron | ShrubNativeWater-wise | Fast; irritating hairs; dry bank. |
| Toyon Heteromeles arbutifolia | ShrubNativeWater-wise | Red berries; fire-resistant hedge. |
| Lemonade berry Rhus integrifolia | ShrubNativeWater-wise | Coastal hedge; tough. |
| Desert willow Chilopsis linearis | TreeNativeWater-wise | Monsoon; summer flowers. |
| Creosote bush Larrea tridentata | ShrubNativeWater-wise | Desert; allelopathic; no irrigation. |
| Yucca Yucca | SucculentWater-wiseNative | Drainage; architectural flower spikes. |
| Agave Agave | SucculentWater-wise | Sharp drainage; full sun. |
| Prickly pear Opuntia | SucculentWater-wiseNative | Pads root easily; full sun. |
| California poppy Eschscholzia californica | AnnualNativeWater-wise | Seed onto bare soil in autumn. |
| Matilija poppy Romneya coulteri | PerennialNativeWater-wise | Spreads by rhizome; dry bank. |
| Penstemon Penstemon | PerennialNativeWater-wise | Fast drainage; short-lived. |
| English lavender Lavandula angustifolia | ShrubHerbWater-wise | Full sun, sharp drainage; no summer water. |
| Garden rose Rosa | ShrubCut flower | Heat-tolerant cultivars; irrigation and mulch. |
| Monkeyflower Diplacus | ShrubNative | Winter–spring flowers; summer dormancy. |
| Olive Olea europaea | TreeFruitWater-wise | Heat and drought; fruitless cultivars for patios. |
| Citrus Citrus | FruitTree | Frost-tender; sheltered wall or container. |
| Grape Vitis vinifera | VineFruit | Dry summer; deep roots. |
| Almond Prunus dulcis | NutTree | Early blossom; frost risk. |
| Tomato Solanum lycopersicum | VegetableAnnual | Full sun; drip irrigation. |
| Lettuce Lactuca sativa | Vegetable | Cool season; afternoon shade in hot valleys. |
| Bermudagrass Cynodon dactylon | Turf | Warm-season; water budget. |
| Gramagrass Bouteloua | GrassNativeWater-wise | Low-water lawn alternative. |
| Muhly grass Muhlenbergia | GrassNativeWater-wise | Warm-season; autumn colour. |
The eight disciplines here
| Discipline | What it looks like here | Taxa | Read |
|---|---|---|---|
| Garden Design 01 | Palette and practice for garden design in this climate. | 22 | Discipline guide |
| Floriculture 02 | Palette and practice for floriculture in this climate. | 6 | Discipline guide |
| Vegetables & Herbs 03 | Palette and practice for vegetables & herbs in this climate. | 5 | 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. | 8 | Discipline guide |
| Turfgrass 06 | Palette and practice for turfgrass in this climate. | 1 | Discipline guide |
| Nursery & Propagation 07 | Palette and practice for nursery & propagation in this climate. | 19 | Discipline guide |
| Water-wise & Restoration 08 | Palette and practice for water-wise & restoration in this climate. | 23 | Discipline guide |
Professional bodies and standards
Association of Professional Landscape Designers (APLD) · California Native Plant Society (CNPS) · International Society of Arboriculture (ISA)
Design idiom
Mid-century modern, xeriscape, courtyard.
Sources
Other regions
US Southeast · Tropical Latin America · Andes & South America · Africa · all 16 regions