Generally — Most Areas
subterranean clover (zones 6-10) suits most of Massachusetts (5a-7b) — zones 6-7 are in range, and the rest of the state is the exception.
Subterranean Clover in Massachusetts — the short answer
Subterranean Clover in Massachusetts: hardy in zones 6–10, full sun, against a state median of ~206 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
- Massachusetts zones
- 5a-7b
- USDA PHZM 2023
- Frost window
- Apr 4 - Apr 14 – Oct 24 - Nov 14
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 171 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 Massachusetts site runs ~206 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.
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Massachusetts is not one climate
A single Massachusetts answer averages 14 counties whose growing seasons are 75 days apart — from 171 frost-free days in Berkshire County to 246 in Nantucket 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 193–226 days, with a median of 205 days — a 75-day span end to end.
Measured across 14 Massachusetts 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 in Massachusetts Fits Best
Subterranean Clover is rated for zones 6–10 — a cold floor USDA puts at -10 to 0°F. Against Massachusetts’s 14 counties that band holds in 13 of them, and the line runs at Franklin County (zone 6a), the coldest county still inside it.
Inside zones 6–10
13 counties
- Hampshire County · zone 6a
- Worcester County · zone 6a
- Essex County · zone 6b
3 of 13 shown
Below the zone 6 floor
1 county
- Berkshire County · zone 5b
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.
Even within Massachusetts's zones 5a-7b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for subterranean clover (USDA PHZM 2023):
Zone Comparison
Subterranean Clover Needs
- USDA Zones: 6-10
- Frost-Free Days: 120+
- Sun: Full Sun
- Mature size: 6 in tall
- Drought tolerance: Medium
Massachusetts Has
- USDA Zones: 5a-7b
- Last Hard Freeze (28°F): Apr 4 - Apr 14
- First Hard Freeze (28°F): Oct 24 - Nov 14
- Annual Rainfall: 42-50 inches
- Common Soils: Glacial till, Sandy loam, Rocky 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 Massachusetts
The frost window
Across Massachusetts, the last spring hard freeze (28°F) clears between Apr 4 and Apr 14, and the first fall hard freeze lands between Oct 24 and Nov 14 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 193-day window you can count on — up to 224 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 Massachusetts'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 — Massachusetts'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 103 days to spare even in Massachusetts's tightest freeze scenario — room for a later start or a second sowing.
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 Massachusetts, 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 Massachusetts site sees ~206 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Subterranean Clover needs ~800 GDD (base 50°F) to ripen. The state median runs ~2506 GDD (from PRISM 1991-2020 climate normals), so Massachusetts'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 Massachusetts. 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 Massachusetts soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Massachusetts site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
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. Massachusetts 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 Massachusetts
Zone compatibility tells you about winter cold survival — but Massachusetts growers also need to think about:
Short growing season (120-180 frost-free days) limits warm-season crops
Rocky glacial soils require amendment in many areas
Late spring frosts can damage early plantings through mid-May
Deer pressure is significant in suburban and rural areas
What to actually do about these — and the constraints that apply to every Massachusetts grower, not just subterranean clover — is covered on the Massachusetts growing guide.
Timing shifts within Massachusetts
Subterranean Clover needs about 120 days of frost-free season to complete its cycle. Even Berkshire County — Massachusetts’s shortest season at 171 frost-free days — clears that by 51 days, so season length isn’t the constraint anywhere in Massachusetts. What varies is your own parcel.
Across Massachusetts’s 14 counties the frost-free season runs from 171 days in Berkshire County to 246 days in Nantucket County — a spread of 75 days, which is why a single statewide planting date misleads. The median Massachusetts county sees 206 frost-free days, leaving subterranean clover about 86 days of slack on a typical parcel — room for a second sowing where the season runs long.
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 Massachusetts's frost window — roughly 206 days, opening after the last 28°F freeze (Apr 4 - Apr 14) and closing at the first (Oct 24 - Nov 14), per NOAA Regional Climate Centers ACIS, 1991-2020.
Massachusetts Cooperative Extension
For Massachusetts-specific cultivar recommendations, planting calendars, and pest pressure for subterranean clover, the canonical source is UMass Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Subterranean Clover native to Massachusetts?
No — the USDA PLANTS Database lists Subterranean Clover as introduced rather than native in the Lower 48, so it is not part of Massachusetts's native flora. It grows here as a garden plant; pairing it with a few Massachusetts natives keeps local pollinators fed too.
Looking for plants that belong here? The Massachusetts 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 Massachusetts
When can I plant Subterranean Clover in Massachusetts?
Massachusetts's last spring hard freeze (28°F) clears between Apr 4 and Apr 14, and the first fall hard freeze lands between Oct 24 and Nov 14 (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 Massachusetts?
Yes — Subterranean Clover matures in 90 days (Growable Ground Plant Database), and Massachusetts's dependable hard-freeze-free window runs 193 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 103 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 Massachusetts?
Massachusetts spans USDA hardiness zones 5a-7b (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 Massachusetts site have?
A typical Massachusetts site sees ~206 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.
Is Subterranean Clover native to Massachusetts?
No — the USDA PLANTS Database lists Subterranean Clover as introduced rather than native in the Lower 48, so it is not part of Massachusetts's native flora. It grows here as a garden plant; pairing it with a few Massachusetts natives keeps local pollinators fed too.
How should I amend the soil for Subterranean Clover in Massachusetts?
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 Massachusetts site — amend for drainage and organic matter first.
Will Subterranean Clover actually grow on my specific land in Massachusetts?
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 Massachusetts
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 Massachusetts subterranean clover averages can't show:
We read public map data around Massachusetts — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Massachusetts subterranean clover average
Explore More
Growing guides for subterranean clover
Explore Massachusetts county by county
Massachusetts 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 Massachusetts 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 Massachusetts
Massachusetts has a growing page for 893 plants — a rotating sample of the rest of the shelf.
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