The Klamath Basin spans USDA hardiness zones 6a-8a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
A high-desert basin straddling the Oregon–California line and watered by the federal Klamath Project — potatoes, onions, alfalfa hay, and small grains grown on cold, short-season ground where interior frosts can squeeze the growing window under 90 days. Crops well matched to these conditions include tomato, kale, douglas fir, and garlic — though what thrives on any one site still turns on its specific soil, sun, and drainage.
The Klamath Basin spans California and Oregon.
Your yard isn't all of the Klamath Basin.
The Klamath Basin spans USDA zones 6a-8a, but your parcel sits in exactly one — and slope, tree cover, and low spots nudge it further. 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 Klamath Basin — soil, climate, flood, and parcel records. How we handle your address.
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The Klamath Basin — the short answer
The Klamath Basin: USDA zones 6a-8a, 86–210 frost-free days depending where in it you stand, across 2 states.
- USDA zones
- 6a-8a
- USDA PHZM 2023, aggregated over the footprint
- Shortest season here
- 86 days
- NOAA Regional Climate Centers ACIS, 1991-2020 — Klamath County
- Counties
- 3
- US Census TIGER/Line 2025
- Region type
- County cluster
- Growable Ground growing-region registry
Region boundary: Growable Ground growing-region registry — curated county clusters, EPA Level III ecoregions, and town clusters drawn finer than any county. The season figure is this region's own record, measured across its 3 member counties, not a state or national average.
Hardiness Zone Range
The Klamath Basin is not one growing season
One answer for the Klamath Basin averages 3 counties whose growing seasons are 124 days apart — from 86 frost-free days in Klamath County to 210 in Siskiyou County. That is the same region, measured the same way, in the same years. Which end of it your land sits nearer decides what finishes before the first hard freeze.
The middle half of 3 counties runs 125–187 days, with a median of 164 days — a 124-day span end to end.
Measured across 3 member counties, each carrying its own 28°F normal. NOAA Regional Climate Centers ACIS, 1991-2020. A member with no own record is absent from the range rather than counted as zero — nothing here is interpolated to the region. Your own site sits somewhere inside this range; a parcel report resolves where.
Where the line runs inside the Klamath Basin
The middle half of the Klamath Basin runs 125–187 frost-free days, and 2 of its 3 counties sit outside that — 1 on the short side, 1 on the long. A regional planting date describes the middle well and the ends poorly, which is worth knowing before you follow one.
Under 125 frost-free days
1 county
- Klamath County · 86 days
The end of the region that sets the planting calendar — start seed indoors here and the season stretches to meet the crop.
125–187 frost-free days
1 county
0 of 1 shown
The middle half of the region, and the part a single regional season describes well.
Over 187 frost-free days
1 county
- Siskiyou County · 210 days
Long enough for a second succession of a quick crop after the first comes out.
Each county is placed by its OWN 28°F frost-free normal (NOAA Regional Climate Centers ACIS, 1991-2020), the same figure its own guide page publishes. Elevation, slope and cold-air drainage move a site within its county as well — which is the part only your address resolves.
What Grows in the Klamath Basin
All 1 of the plants below that publish a season requirement clear even Klamath County’s 86 frost-free days — so on season alone, this grid works at both ends of the region. The 124-day spread still decides how far past this list you can push, and how early you can start.
Plants matched to the Klamath Basin's USDA zones 6a-8a, ordered by how much hardiness margin each has across the region — the ones with room to spare at both ends of this band lead. Each links to its full growing profile.
Native Plants of the Klamath Basin
Plants the USDA PLANTS Database documents as native and present in all 2 states this region crosses, kept only where the published hardiness range meets the Klamath Basin’s USDA zones 6a-8a — closest range match first. Presence is recorded by state, so a plant can be documented across the state and still be scarce in your corner of the region.
The ground across the Klamath Basin
The USDA soil survey maps this ground county by county. These are those records weighted by land area across three member counties — this region’s own profile, not a state figure.
The ground is predominantly Mollisols, at 50% of mapped acres, followed by Andisols (22%), Alfisols (8%) and Inceptisols (7%). Nine soil orders appear somewhere inside the footprint, which is the honest reason a regional soil answer only goes so far. The most extensive named soils are Lapine, Lorella, and Steiger.
58% of those acres are well drained, and another 10% excessively drained, 7% somewhat excessively drained. Topsoil pH runs 6.3–7.2 between the lowest and the highest county on record.
Soil order
Mollisols
Drainage
Well drained
Topsoil pH
6.3–7.2
Hydric soils
12%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Klamath County holds the most wetland ground here, at 15% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Klamath Basin
The soil survey reads this ground county by county, and the readings above are those records summed across the Klamath Basin. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records58% of the mapped acres across the Klamath Basin are well drained — ground that drains quickly. That is area-weighted across all three of its mapped counties.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
From county recordsTopsoil across the Klamath Basin runs pH 6.3–7.2 — near neutral in all three of them.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Safe to Grow Here?
What the federal record shows across the Klamath Basin — and how to grow with it.
Across the Klamath Basin's 3 counties the federal record holds 1,509 documented sites, mostly Mining (487), Brownfields (469) and Underground Storage Tanks (372). The heaviest single county is Siskiyou County, with 903.
That is a regional count, not a reading of any one lot — proximity to a documented site is information, not a diagnosis. Open the map outlined to the Klamath Basin to see which records sit where you actually grow.
Sources Checked
Summed across the 3 counties in the Klamath Basin
A note from Gnorman
What an experienced grower watches for around here
In and around the Klamath Basin, Mining runs higher than the national average — 487 sites across the 3 counties in the Klamath Basin. That's not a problem with your land — it's information about it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Klamath Basin
Everything above resolves to the Klamath Basin as a whole — a footprint whose own counties record seasons 124 days apart, and hardiness across zones 6a-8a. Your parcel sits at one point in that range, not in the middle of it. 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 region 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 regional average.
Your Lot vs the Klamath Basin Average
Klamath Basin Average
- ●USDA Zones 6a-8a, averaged across Klamath Basin
- ●One soil character for all of Klamath Basin
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Klamath Basin's 6a-8a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Klamath Basin
Pull a site-specific report for your exact address in the Klamath Basin — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Klamath Basin averages can't show:
We read public map data around The Klamath Basin — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Klamath Basin average
How we know this about the Klamath Basin
The boundary: a cluster of neighboring counties. Growing regions have no official boundary, so this footprint is our published one, and every figure on this page was measured over the counties inside it rather than borrowed from the state around it.
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, aggregated across the footprint; the growing season from NOAA Regional Climate Centers ACIS 1991–2020 28°F normals, read at each member’s own record; boundaries from US Census TIGER/Line 2025; the contamination record from the federal sources named in that beat above; the soil from the USDA NRCS SSURGO survey, read at each member county’s own record and weighted to this footprint by land area. Where a member carries no record of its own, it is absent from the figure rather than filled in.
Common questions about the Klamath Basin
What hardiness zone is the Klamath Basin?
The Klamath Basin spans USDA hardiness zones 6a-8a, aggregated from the USDA Agricultural Research Service Plant Hardiness Zone Map 2023 across the region's counties. Zones reflect average annual extreme minimum temperatures from 1991–2020 data.
How long is the growing season in the Klamath Basin?
Measured between 28°F hard freezes, the Klamath Basin's counties mostly run 125 to 187 frost-free days, median 164 (NOAA Regional Climate Centers ACIS, 1991–2020, over 3 member counties). That 62-day spread is the honest read — no single season describes 3 counties, and each county guide below carries its own.
When does frost risk end in the Klamath Basin?
Across the Klamath Basin, the middle half of member counties see their last 28°F hard freeze between Apr 21 and May 22 (median May 4), and their first fall freeze between Sep 24 and Oct 25. Those are hard freezes, not the last light frost: tender transplants wait for about May 25, and elevation decides which end of a 31-day spread you garden in.
What grows well in the Klamath Basin?
The Klamath Basin's conditions suit plants such as Tomato, Kale, Douglas Fir, Garlic, Almond, Persimmon. What actually thrives on any one site still turns on its specific soil, sun, and drainage — we score each plant against the real conditions at your address.
How is the Klamath Basin defined?
The Klamath Basin is defined here as a curated cluster of 3 neighboring counties that share a growing character. Growing regions have no official boundary, so this footprint is our published one — every county in it is named on this page.
Which states does the Klamath Basin cover?
The Klamath Basin spans California and Oregon. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Pacific Northwest, Columbia Basin, California Central Valley, Willamette Valley, Sacramento Valley, and San Joaquin Valley share at least one state with the Klamath Basin. Growing regions overlap and interlock — a single address can sit inside more than one, which is why the precise read is always the parcel, not the region.
What this page reads at the Klamath Basin’s own scale
6 of the readings below were taken at the Klamath Basin's own scale — the zone 6a-8a band across its footprint, a median 164-day season across its 3 counties and 1,509 documented federal contamination records across its 3 counties, 903 of them in Siskiyou County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 6a-8a aggregated across all 3 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 3 counties this region is curated fromGrowable Ground subregion registry
- The growing character that makes this region distinct from the states it crossesGrowable Ground subregion registry
- The 28°F season across the footprint — the middle half of its 3 counties run 125 to 187 frost-free days, median 164NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 1,509 documented federal contamination records across its 3 counties, 903 of them in Siskiyou County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 50% Mollisols, topsoil pH 6.3–7.2, area-weighted across its 3 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — all 2 member states' curated sets, merged and filtered to zones 6a-8afrom California and Oregon
What this page can’t tell you
- Which end of the 62-day range your ground sits at — 125 days at one extreme, 187 at the other, decided mostly by elevationfrost dates explained →
- Which of those soils your own ground sits on — the survey maps them county-wide, and they change across a drivewaysoil types explained →
- The soil pH, drainage, sun hours, and frost pockets on one specific lotwhy one lot differs from the next →
Explore the Klamath Basin
State growing guides
Counties in this region
Other growing regions across California and Oregon
The maritime Northwest west of the Cascade crest — mild, wet winters and dry summers behind berries, tree fruit, and lush cool-season gardens. (Union of the west-side ecoregions.)
A dry basalt plateau of loess soils in the inland Northwest where irrigation turns arid ground into apple, cherry, hop, and wine-grape country.
A vast flat alluvial trough with hot dry summers and rich soils — one of the most productive agricultural regions on earth, from almonds and stone fruit to row crops.
Oregon's broad maritime valley pairs deep alluvial soils with cool wet winters and dry summers — the heart of the state's hazelnut, berry, and Pinot country.
The cooler, wetter northern half of the Central Valley — rice, walnuts, tomatoes, and orchard fruit on rich alluvial bottomland.
The hot southern half of California's Central Valley — deep soils and intense sun behind almonds, stone fruit, grapes, and row crops at vast scale.