Glenn County, in California, sits in USDA hardiness zone 9a — a zone band wide enough that plant choice, not possibility, is the interesting question.
A short list that earns its place here — avocado, meyer lemon, tomato, and grape — with any one site's soil, sun, and drainage making the final cut.
Glenn County lies within the Sacramento Valley — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring
Glenn County holds more than one microclimate.
Soils and elevations shift across Glenn County, so your frost dates and drainage aren't the county average. Enter your address and we'll score 1,112 plants against your land's actual soil, sun, and frost.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Quick Facts
USDA Zones
9a
Last Frost (state avg.)
Jan 15 - May 15
First Frost (state avg.)
Oct 1 - Dec 31
County Area
841K acres
Hardiness Zone Range
Growing Season
Zone maps are averages across Glenn County. Your yard's slope, trees, and frost pockets shift what actually grows — see your land's exact reading.
Soil in Glenn County
Across Glenn County, the ground is predominantly Alfisols, where Sheetiron, Maymen, and Tehama are the most extensive named soil series. The soil is generally well drained with a gravelly loam surface. Topsoil pH runs about 5.8–6.7, slightly acidic. Rainfall drains through hydrologic group D soils.
Soil order
Alfisols
Drainage
Well drained
Hydric soils
9%
Soil still varies lot by lot — soil types explained.
What Grows in Glenn County
Plants matched to Glenn County's USDA zones 9a — each links to its full growing profile.
Growing Challenges in California
What an experienced grower plans around here — each one has a move.
Drought is a persistent challenge — irrigation is essential in most regions
Design the water system before the plants: drip lines plus a thick mulch layer run a full garden on surprisingly little water.
Wildfire risk affects rural and foothill properties
Keep plantings low, lean, and well-watered near structures — your extension office publishes firewise landscaping guides for your county.
Adobe clay soils in valleys drain poorly without amendment
Work in compost over seasons, or skip the fight with a raised bed — adobe's nutrients are excellent once drainage is solved.
Wide climate variation means plant selection is highly location-specific
Zones run 5a to 11a in one state — check your exact zone before trusting any statewide planting list.
For cultivar selection, pest pressure, and planting-time guidance specific to California, the UC Agriculture and Natural Resources is the authoritative local source.
Safe to Grow Here?
What the federal record shows across Glenn County — and how to grow with it.
We checked the federal record across Glenn County — 815 documented sites across 7 of the 9 source types we track.
The most significant on record: 2 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
There's a meaningful federal record across Glenn County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Environmental Intelligence
Understanding what's nearby helps you make informed decisions about where and how to grow.
Sources Checked
across Glenn County
Severity Distribution
across Glenn County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Glenn County, Nitrate runs higher than the national average — 394 sites nearby. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Glenn County
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,112 plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Your Specific Parcel Matters
Glenn County Average
- ●USDA Zones 9a
- ●Generic soil type for the area
- ●State-average frost dates
YOUR Parcel
- ✓Your exact hardiness zone
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Glenn County
Pull a site-specific report for your exact address in Glenn County, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Key Growing Facts for Glenn County, California
- USDA Hardiness Zones: 9a (USDA PHZM 2023)
- Last Spring Frost (state avg.): Jan 15 - May 15 (NOAA 30-Year Climate Normals)
- First Fall Frost (state avg.): Oct 1 - Dec 31 (NOAA 30-Year Climate Normals)
- County Land Area: 841K acres (US Census TIGER 2025)
Zone data: USDA ARS Plant Hardiness Zone Map 2023. Climate data: NOAA NCEI. County boundaries: US Census TIGER/Line 2025.
Frost dates here are the Glenn County average. Low spots and tree cover move them by days on any one yard — see your exact frost windows.
Frequently Asked Questions
What hardiness zone is Glenn County, California?
Glenn County sits in USDA hardiness zone 9a, per the USDA Plant Hardiness Zone Map 2023. Zones reflect average annual extreme minimum temperatures from 1991–2020 weather data.
When does frost risk typically end in Glenn County?
Glenn County follows California's statewide frost window: last spring frost around Jan 15 - May 15 and first fall frost around Oct 1 - Dec 31, per NOAA 30-year climate normals (1991–2020). Frost dates shift with elevation and local microclimate, so watch your own site's cold pockets.
What vegetables grow in Glenn County?
Glenn County's zone 9a supports a wide range — strong performers include Avocado, Meyer Lemon, Tomato, Grape, and Fig. What actually takes on any one site comes down to its soil, sun, and drainage, and we score each plant against the real conditions at your address.
Which hardiness zone is Glenn County, really?
Officially, Glenn County sits in USDA zone 9a (USDA PHZM 2023) — but a zone is a 30-year average of winter's coldest night across an area, and it can't see any one yard. A south-facing slope, a tree line, or a low frost pocket can shift a single site by half a zone either way, which is why neighboring gardeners often quote different numbers. We read the conditions at your exact address — soil, sun, slope, and frost — and score 1,112 plants against what's actually there.
Is the soil safe to grow vegetables in Glenn County?
The federal record around Glenn County is a meaningful one — 815 documented sites — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
Just moved to Glenn County — what should I know before planting?
Start with three facts. Glenn County sits in USDA zone 9a, which sets what survives winter; the statewide frost window runs about Jan 15 - May 15 to Oct 1 - Dec 31 (NOAA 30-year climate normals); and 815 documented sites sit on the federal record here, so a soil test before food beds is the smart first step. From there, matching plants to your actual soil and sun is the fun part.
Everything on this page is a Glenn County average. Your yard writes its own version — we read soil, sun, drainage, and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads California's frost window, season length, and soil profile against the plant's real requirements.