Conditional — Some Areas
subterranean clover (zones 6-10) reaches only part of Vermont (4a-6a): zone 6 are in range, so where you are in the state decides it.
One zone short — what would close it
Subterranean Clover is hardy to zone 6, and the warmest ground in Vermont is zone 5 — 1 zone short. Planted in open ground it will not survive a Vermont winter. To grow it here, grow subterranean clover in a hoop house or unheated greenhouse — its modeled 1.5-zone lift covers this gap.
A hoop house or unheated greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 6-10 (plant) against 3-5 (Vermont). Lift modeled by crop_engine.GREENHOUSE_ZONE_MODIFIER_BY_SUBTYPE['hoop_house'] (+1.5 zones) via api/fast_sections.py Unlock Engine v2.
Subterranean Clover in Vermont — the short answer
Subterranean Clover in Vermont: hardy in zones 6–10, full sun, against a state median of ~163 frost-free days.
- Plant zones
- 6-10
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Vermont zones
- 4a-6a
- USDA PHZM 2023
- Frost window
- Apr 27 - May 5 – Oct 10 - Oct 17
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 146 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
- Days to maturity
- 90 days
- Growable Ground Plant Database
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
Subterranean Clover is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Vermont site runs ~163 frost-free days, but that is a state median, not your yard: slope, trees, and low spots move the last-frost date across a single parcel. Enter your address and we'll score subterranean clover against your land's actual frost dates, sun, and soil.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Vermont is not one climate
A single Vermont answer averages 14 counties whose growing seasons are 44 days apart — from 146 frost-free days in Essex County to 190 in Grand Isle County. Which end of that your land sits nearer changes what subterranean clover can finish before the first hard freeze.
The middle half of 14 counties runs 158–173 days, with a median of 161 days — a 44-day span end to end.
Measured across 14 Vermont counties. NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze. Quartiles are order statistics — every figure shown is a value a real county recorded, not an interpolation. Your own site sits somewhere inside this range; a parcel report resolves where.
Where Subterranean Clover Stands in Vermont
Subterranean Clover is rated for zones 6–10 — a cold floor USDA puts at -10 to 0°F. No Vermont county sits inside it, so in open ground this is a grown-under-cover plant here rather than a bed plant — which is a statement about Vermont winters, not about subterranean clover.
Below the zone 6 floor
14 counties
- Caledonia County · zone 4b
- Essex County · zone 4b
- Franklin County · zone 4b
3 of 14 shown
Winter cold is the limit here — the same plant works in a container that comes under cover.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. A zone is a 10°F band of average annual extreme minimum temperature, so the floor above is the band the plant's rating denotes, not a single measured kill point. Slope, shelter and cold-air drainage routinely move a site half a zone either way from its county figure — which is the part only your address resolves.
Zone Comparison
Subterranean Clover Needs
- USDA Zones: 6-10
- Frost-Free Days: 120+
- Sun: Full Sun
- Mature size: 6 in tall
- Drought tolerance: Medium
Vermont Has
- USDA Zones: 4a-6a
- Last Hard Freeze (28°F): Apr 27 - May 5
- First Hard Freeze (28°F): Oct 10 - Oct 17
- Annual Rainfall: 34-44 inches
- Common Soils: Glacial till, Clay, Silt loam
Plant Zone Range (zones 6-10)
Preferred Soil pH
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Subterranean Clover in Vermont
The frost window
Across Vermont, the last spring hard freeze (28°F) clears between Apr 27 and May 5, and the first fall hard freeze lands between Oct 10 and Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 158-day window you can count on — up to 173 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
Frost hardiness
Subterranean Clover takes cold down to about 10°F before a freeze kills it (FAO ECOCROP), so you can plant on the early side of Vermont's window — even a few weeks before the final hard freeze. That is the point where cold damages growing tissue, not a winter-survival floor — an established perennial comes through far colder while dormant, which is what its hardiness zone tells you.
When to start the seed
Subterranean Clover is direct-sown where it grows rather than started under cover, so there is no seed-tray head start to bank — Vermont's dates above are the whole calendar for it. That makes the last-freeze date the binding constraint, and a warmer pocket of your own yard is worth more to this crop than it is to a transplanted one.
Days to maturity vs. the window
At 90 days to maturity (Growable Ground Plant Database), counting from the last hard freeze it ripens with 68 days to spare even in Vermont's tightest freeze scenario — room for a later start or a second sowing.
Timing tuned to sub-state frost dates — Essex County, not the statewide average.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says subterranean clover survives winter in part of Vermont, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Subterranean Clover wants 120+ frost-free days; a typical Vermont site sees ~163 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves a workable window — start indoors to bank time.
Growing degree days
Subterranean Clover needs ~800 GDD (base 50°F) to ripen. The state median runs ~1746 GDD (from PRISM 1991-2020 climate normals), so Vermont's typical season clears that easily.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Subterranean Clover tolerates a wide pH range (pH 5-8) — 3 units, acid ground through alkaline — so soil acidity is rarely what limits it in Vermont. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. It will grow across that whole span, but it does best between pH 5.5 and 6.5 — worth knowing before you decide whether a Vermont soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Vermont site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
SSURGO maps about 18.5% of Vermont as poorly or somewhat-poorly drained, and the class flips parcel to parcel. Subterranean Clover sits mid-range for drought tolerance, so either extreme can cost you — your soil map unit, not the state average, is the real answer.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Vermont soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Subterranean Clover in Vermont
Zone compatibility tells you about winter cold survival — but Vermont growers also need to think about:
Short growing season (100-130 frost-free days)
Rocky soils throughout the Green Mountains
Heavy clay in the Champlain Valley
Growing subterranean clover here specifically
Subterranean Clover rates to USDA zones 6–10 and takes frost damage on growing tissue around 10°F (FAO ECOCROP), but cold isn't the risk in Vermont — wet is: with roughly 18.5% of its soils poorly-drained (SSURGO), soggy ground rots the roots.
Give subterranean clover a raised bed or mounded row with coarse amendment so its roots never sit wet. How to handle it →
What to actually do about these — and the constraints that apply to every Vermont grower, not just subterranean clover — is covered on the Vermont growing guide.
Timing shifts within Vermont
Vermont isn't one climate. In Essex County, the last hard freeze (28°F) holds until about May 13 — roughly 11 days later than the recorded state median — so plant subterranean clover to your county's window, not the statewide date.
Subterranean Clover needs about 120 days of frost-free season to complete its cycle. Even Essex County — Vermont’s shortest season at 146 frost-free days — clears that by 26 days, so season length isn’t the constraint anywhere in Vermont. What varies is your own parcel.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Subterranean Clover's 120-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Subterranean Clover draws honeybees, native bees, and butterflies (high value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, subterranean clover can only work that bloom inside Vermont's frost window — roughly 163 days, opening after the last 28°F freeze (Apr 27 - May 5) and closing at the first (Oct 10 - Oct 17), per NOAA Regional Climate Centers ACIS, 1991-2020.
Vermont Cooperative Extension
For Vermont-specific cultivar recommendations, planting calendars, and pest pressure for subterranean clover, the canonical source is UVM Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Subterranean Clover native to Vermont?
No — the USDA PLANTS Database lists Subterranean Clover as introduced rather than native in the Lower 48, so it is not part of Vermont's native flora. It grows here as a garden plant; pairing it with a few Vermont natives keeps local pollinators fed too.
Looking for plants that belong here? The Vermont growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Subterranean Clover in Vermont
When can I plant Subterranean Clover in Vermont?
Vermont's last spring hard freeze (28°F) clears between Apr 27 and May 5, and the first fall hard freeze lands between Oct 10 and Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020). Subterranean Clover takes cold to about 10°F before a freeze kills it (FAO ECOCROP — the point where cold damages growing tissue, not a winter-survival floor), so plant on the early side of that window — even ahead of the final hard freeze.
Can Subterranean Clover mature before first frost in Vermont?
Yes — Subterranean Clover matures in 90 days (Growable Ground Plant Database), and Vermont's dependable hard-freeze-free window runs 158 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 68 days of margin. Plant once the last hard freeze has passed — two to three weeks later for anything tender — and it ripens ahead of the first fall freeze.
What hardiness zone is Subterranean Clover grown in across Vermont?
Vermont spans USDA hardiness zones 4a-6a (USDA ARS PHZM 2023). Subterranean Clover carries a range of zones 6-10, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Vermont site have?
A typical Vermont site sees ~163 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Subterranean Clover needs 120+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date. In cooler counties like Essex, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Subterranean Clover native to Vermont?
No — the USDA PLANTS Database lists Subterranean Clover as introduced rather than native in the Lower 48, so it is not part of Vermont's native flora. It grows here as a garden plant; pairing it with a few Vermont natives keeps local pollinators fed too.
How should I amend the soil for Subterranean Clover in Vermont?
Subterranean Clover tolerates pH 5-8 and well (dry spells) drainage (Growable Ground Plant Database). That is a 3-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Vermont site — amend for drainage and organic matter first.
Will Subterranean Clover actually grow on my specific land in Vermont?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores subterranean clover against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Vermont
State-level data is a sketch. Your Growable Ground report scores subterranean clover against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Vermont subterranean clover averages can't show:
We read public map data around Vermont — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Vermont subterranean clover average
Explore More
Growing guides for subterranean clover
Explore Vermont county by county
Vermont carries 14 counties with their own USDA zone — a sample of the growing pages for subterranean clover there:
Where else subterranean clover grows
Subterranean Clover's zone band crosses state lines — these are the states closest to Vermont in winter climate where it also has a page, plus the far ends of its range. Each one re-answers the question with that state's own record.
More to grow in Vermont
Vermont has a growing page for 747 plants — a rotating sample of the rest of the shelf.
Analysis by the Growable Ground research team, grounded in USDA PLANTS, USDA NRCS SSURGO, NOAA Climate Normals (1991-2020), and named Cooperative Extension sources. How we know →
Cite this dataset
Kirchick, M. (2026). Growable Ground Plant Database [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21435643
Licensed CC BY-NC 4.0. DOI 10.5281/zenodo.21435643
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