Round Mountain, California, sits in USDA hardiness zone 9a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Growers here do well with artichoke, fig, california poppy, and cabbage — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Round Mountain, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Round Mountain lot. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around Round Mountain — soil, climate, flood, and parcel records. How we handle your address.
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Round Mountain — the short answer
Round Mountain, California: USDA zone 9a, about 285 days between hard freezes, across 1K acres of town.
- USDA zone
- 9a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 23
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Dec 5
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~285
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 1K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 9a is Round Mountain's average, not your lot's — a low corner or a tree line moves it. Against Round Mountain's 285-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Round Mountain
Each reading below is measured for Round Mountain itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredRound Mountain runs about 285 days between hard freezes — close to year-round growing.
Frost is rarely the limit here; winter plantings are as real as summer ones, and the harder question is which crops shrug off the summer heat.
Grow cool-season crops through the mild winter, and choose heat-tolerant varieties for the summer beds.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredRound Mountain sits in USDA hardiness zone 9a.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country Round Mountain is in
Round Mountain sits in the Klamath Mountains/California High North Coast Range — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Round Mountain's own centroid, and it is not what its county reads: Shasta County is mostly Cascades. The wider page above you is answering a different question about different ground.
What Grows in Round Mountain
Every plant below cleared Round Mountain's own zone 9a and its 285-day season. Each card opens that plant's California profile. How we score.
Is it too late to plant in Round Mountain?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Jan 26; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 23 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 5 — long-season crops need about 90 days of runway, quick greens only 30. Here the calendar nearly circles: cool-season crops take the winter shift, and the next window is always close.
What's on the federal record near Round Mountain
Closest first, within ~10 miles of Round Mountain. Listing isn't leaking, and distance isn't exposure.
- INTERNATIONAL LINE BUILDERS, INC.Brownfields · 0.6 mi
- AT&T MOBILITYBrownfields · 0.7 mi
- KLEIN EQUIPMENT SERVICESBrownfields · 0.7 mi
- PG&E ROUND MOUNTAIN SUBSTATIONBrownfields · 0.7 mi
- Highgrade Lead ProspectMining · 1.7 mi
- CartwrightMining · 2.3 mi
- St John ProspectMining · 4.3 mi
- St. JohnMining · 4.3 mi
- 035N001E29F001MNitrate · 5.0 mi
- 035N001E27R001MNitrate · 6.2 mi
- Grotefend Zinc ProspectMining · 6.4 mi
- STRICKLANDS AUTO REPAIRBrownfields · 6.8 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Round Mountain's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near Round Mountain.
Sources Checked
within ~10 miles of Round Mountain
Severity Distribution
within ~10 miles of Round Mountain
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Round Mountain, two things run higher than the national average within ~10 miles of Round Mountain — Mining (37 sites) and Superfund (3 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check your specific parcel in Round Mountain
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the Round Mountain average
Your land is one point inside Round Mountain
Everything above resolves to Round Mountain as a whole — one PHZM band and one 28°F frost record, read across 1K acres. Your parcel is one point inside that footprint. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at town scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better local average.
Your Lot vs the Round Mountain Average
Round Mountain Average
- ●USDA Zones 9a, averaged across Round Mountain
- ●One soil character for all of Round Mountain
- ●Frost dates read at Round Mountain's scale: Feb 23 to Dec 5
YOUR Parcel
- ✓Your exact zone, not Round Mountain's 9a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Round Mountain
Pull a site-specific report for your exact address in Round Mountain, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Round Mountain averages can't show:
We read public map data around Round Mountain — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Round Mountain average
How we know this about Round Mountain
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Round Mountain’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at town grain anywhere on this page — there is no town-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Round Mountain
When does frost risk typically end in Round Mountain?
The last hard freeze (28°F) in Round Mountain typically lands around Feb 23, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about Mar 16.
When is the first frost in Round Mountain?
The first hard freeze (28°F) in Round Mountain typically arrives around Dec 5, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 21, so the watching starts about Nov 5 — about 285 days after the spring freeze cleared.
How long is the growing season in Round Mountain?
Measured between 28°F hard freezes, Round Mountain sees about 285 frost-free days — roughly Feb 23 through Dec 5, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Mar 16 to Nov 21, about 250 days.
Is the soil safe to grow vegetables in Round Mountain?
The federal record around Round Mountain is a meaningful one — 53 documented sites, mostly Mining entries (37), the nearest Brownfields record about 0.6 miles out — 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.
How do I protect my plants from frost in Round Mountain?
From about Nov 5 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Dec 5 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Dec 5. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Round Mountain's scale — its 9a band and its 285-day season. Your yard writes its own version of Round Mountain's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Round Mountain’s own scale
6 of the readings below were taken at Round Mountain's own scale — its own ~285-day season between 28°F freezes, the 1,073 acres it covers and 53 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Round Mountain's own USDA hardiness band, zones 9aUSDA PHZM 2023
- Round Mountain's own 28°F hard-freeze dates, about Feb 23 and Dec 5 and the ~285-day span between themNOAA 1991–2020 Climate Normals
- 53 documented contamination sites on the federal record near Round Mountain, the closest Brownfields record about 0.6 miles out from the town centreFederal environmental registers
- Round Mountain's boundary and the 1,073 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9a and a ~285-day seasonGrowable Ground crop-matching engine
- Round Mountain sits in the Klamath Mountains/California High North Coast Range — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Round Mountain's 1,073 acres read through its county's SSURGO summaryfrom Shasta County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Shasta County
- The growing challenges every California grower plans around — written at state scale, so they stay on the state guidefrom California
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Shasta County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Round Mountain's 1,073 acreswhy one lot differs from the next →
- Which side of Round Mountain you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,073 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.6 miles out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Round Mountain-wide figureread your own land →
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