Silt, Colorado, sits in USDA hardiness zone 6a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Reliable performers under these conditions include cabbage, blackberry, california poppy, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Even in Silt, 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 Silt 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 Silt — soil, climate, flood, and parcel records. How we handle your address.
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Silt — the short answer
Silt, Colorado: USDA zone 6a, about 171 days between hard freezes, across 1K acres of town.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 26
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 14
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~171
- 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 6a is Silt's average, not your lot's — a low corner or a tree line moves it. Against Silt's 171-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Silt
Each reading below is measured for Silt itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSilt runs about 171 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredSilt sits in USDA hardiness zone 6a.
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 Silt is in
Silt sits in the Colorado Plateaus — EPA Level III, inside the wider North American Deserts. That is read at Silt's own centroid rather than borrowed from Garfield County.
What Grows in Silt
Every plant below cleared Silt's own zone 6a and its 171-day season. Each card opens that plant's Colorado profile. How we score.
Is it too late to plant in Silt?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 29; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 26 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 14 — long-season crops need about 90 days of runway, quick greens only 30. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
What's on the federal record near Silt
Closest first, within ~10 miles of Silt. Listing isn't leaking, and distance isn't exposure.
- Go-Fer Foods Of SiltUnderground Storage Tanks · 300 ft
- Tims LLCUnderground Storage Tanks · 550 ft
- Kum & Go #905Underground Storage Tanks · 550 ft
- Silt StationUnderground Storage Tanks · 850 ft
- Silt Food StopUnderground Storage Tanks · 1100 ft
- SILT MERCURYSuperfund · 1100 ft
- Doug Wight Heavy Equipment RepairUnderground Storage Tanks · 1100 ft
- Garfield County Road & Bridge DepartmentUnderground Storage Tanks · 1400 ft
- Valley Farms IncUnderground Storage Tanks · 1900 ft
- Master Petroleum CoUnderground Storage Tanks · 2100 ft
- BLM COLORADO RIVER VALLEY FIELD OFFICEBrownfields · 2300 ft
- SC00609203BCBB GRFLN8Nitrate · 1.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Silt'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 Silt.
Total Sites
143
within ~10 miles of Silt
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Silt
Severity Distribution
within ~10 miles of Silt
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Silt, Nitrate runs higher than the national average — 42 sites within ~10 miles of Silt. 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 Silt
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 Silt average
Your land is one point inside Silt
Everything above resolves to Silt 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 Silt Average
Silt Average
- ●USDA Zones 6a, averaged across Silt
- ●One soil character for all of Silt
- ●Frost dates read at Silt's scale: Apr 26 to Oct 14
YOUR Parcel
- ✓Your exact zone, not Silt's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Silt
Pull a site-specific report for your exact address in Silt, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Silt averages can't show:
We read public map data around Silt — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Silt average
How we know this about Silt
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 Silt’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 Silt
When does frost risk typically end in Silt?
The last hard freeze (28°F) in Silt typically lands around Apr 26, 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 May 17.
When is the first frost in Silt?
The first hard freeze (28°F) in Silt typically arrives around Oct 14, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 30, so the watching starts about Sep 14 — about 171 days after the spring freeze cleared.
How long is the growing season in Silt?
Measured between 28°F hard freezes, Silt sees about 171 frost-free days — roughly Apr 26 through Oct 14, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 17 to Sep 30, about 136 days.
Is the soil safe to grow vegetables in Silt?
The federal record around Silt is a meaningful one — 143 documented sites, mostly Underground Storage Tanks entries (61), the nearest Underground Storage Tanks record under a tenth of a mile 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 Silt?
From about Sep 14 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 Oct 14 (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 Oct 14. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Silt's scale — its 6a band and its 171-day season. Your yard writes its own version of Silt'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 Silt’s own scale
6 of the readings below were taken at Silt's own scale — its own ~171-day season between 28°F freezes, the 1,076 acres it covers and 143 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Silt's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Silt's own 28°F hard-freeze dates, about Apr 26 and Oct 14 and the ~171-day span between themNOAA 1991–2020 Climate Normals
- 143 documented contamination sites on the federal record near Silt, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Silt's boundary and the 1,076 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~171-day seasonGrowable Ground crop-matching engine
- The ecoregion at Silt's own centroid, the Colorado PlateausUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Silt's 1,076 acres read through its county's SSURGO summaryfrom Garfield County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Garfield County
- The growing challenges every Colorado grower plans around — written at state scale, so they stay on the state guidefrom Colorado
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Garfield County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Silt's 1,076 acreswhy one lot differs from the next →
- Which side of Silt you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,076 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record under a tenth of a mile 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 Silt-wide figureread your own land →
More in Colorado
Wider growing context
What grows across ColoradoSilt sits outside our named growing regions, so Colorado as a whole is its closest context here.
Nearby growing guides