San Mar, Maryland, sits in USDA hardiness zone 7a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Reliable performers under these conditions include cabbage, hazelnut, california poppy, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Even in San Mar, 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 San Mar 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 San Mar — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
San Mar — the short answer
San Mar, Maryland: USDA zone 7a, about 225 days between hard freezes, across 298 acres of town.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 30
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 10
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~225
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 298 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 7a is San Mar's average, not your lot's — a low corner or a tree line moves it. Against San Mar's 225-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in San Mar
Each reading below is measured for San Mar itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSan Mar runs about 225 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredSan Mar sits in USDA hardiness zone 7a.
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 San Mar is in
San Mar sits in the Ridge and Valley — EPA Level III, inside the wider Eastern Temperate Forests. That is read at San Mar's own centroid rather than borrowed from Washington County.
What Grows in San Mar
Every plant below cleared San Mar's own zone 7a and its 225-day season. Each card opens that plant's Maryland profile. How we score.
Is it too late to plant in San Mar?
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 2; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 30 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 10 — long-season crops need about 90 days of runway, quick greens only 30. With a season this long, “too late” mostly means “switch crops” — second sowings and a full fall garden are the norm, with garlic closing the year.
Documented around San Mar
Spotted lanternfly documented 0 miles from San Mar, first recorded 2021. What to watch for.
What's on the federal record near San Mar
Closest first, within ~10 miles of San Mar. Listing isn't leaking, and distance isn't exposure.
- CENTRAL PRECISION, INC.Brownfields · 750 ft
- CENTRAL PRECISION, INC.Toxics Release Inventory · 750 ft
- Fahrney-Keedy Memorial Home, Inc.Underground Storage Tanks · 2000 ft
- San Marchildren's Home, Inc.Underground Storage Tanks · 2000 ft
- Webber's GroceryUnderground Storage Tanks · 0.8 mi
- WA Cj 18Nitrate · 1.2 mi
- Old Antiques & GiftsUnderground Storage Tanks · 1.2 mi
- KLINE RICHARD FBrownfields · 1.2 mi
- WA Cj 8Nitrate · 1.2 mi
- MDOT SHA BRIDGE # 2112703Brownfields · 1.3 mi
- Martin Marietta AggregatesUnderground Storage Tanks · 1.3 mi
- MARTIN MARIETTA BOONSBOROBrownfields · 1.3 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from San Mar'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 San Mar.
Sources Checked
within ~10 miles of San Mar
Severity Distribution
within ~10 miles of San Mar
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around San Mar, Nitrate runs higher than the national average — 282 sites within ~10 miles of San Mar. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
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 San Mar
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 San Mar average
Your land is one point inside San Mar
Everything above resolves to San Mar as a whole — one PHZM band and one 28°F frost record, read across 298 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 San Mar Average
San Mar Average
- ●USDA Zones 7a, averaged across San Mar
- ●One soil character for all of San Mar
- ●Frost dates read at San Mar's scale: Mar 30 to Nov 10
YOUR Parcel
- ✓Your exact zone, not San Mar's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in San Mar
Pull a site-specific report for your exact address in San Mar, Maryland — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that San Mar averages can't show:
We read public map data around San Mar — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the San Mar average
How we know this about San Mar
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 San Mar’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 San Mar
When does frost risk typically end in San Mar?
The last hard freeze (28°F) in San Mar typically lands around Mar 30, 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 Apr 20.
When is the first frost in San Mar?
The first hard freeze (28°F) in San Mar typically arrives around Nov 10, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 27, so the watching starts about Oct 11 — about 225 days after the spring freeze cleared.
How long is the growing season in San Mar?
Measured between 28°F hard freezes, San Mar sees about 225 frost-free days — roughly Mar 30 through Nov 10, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 20 to Oct 27, about 190 days.
Is the soil safe to grow vegetables in San Mar?
The federal record around San Mar is a meaningful one — 988 documented sites, mostly Underground Storage Tanks entries (402), the nearest Brownfields record about 0.1 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 San Mar?
From about Oct 11 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 Nov 10 (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 Nov 10. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at San Mar's scale — its 7a band and its 225-day season. Your yard writes its own version of San Mar'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 San Mar’s own scale
7 of the readings below were taken at San Mar's own scale — its own ~225-day season between 28°F freezes, the 298 acres it covers and 988 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- San Mar's own USDA hardiness band, zones 7aUSDA PHZM 2023
- San Mar's own 28°F hard-freeze dates, about Mar 30 and Nov 10 and the ~225-day span between themNOAA 1991–2020 Climate Normals
- 988 documented contamination sites on the federal record near San Mar, the closest Brownfields record about 0.1 miles out from the town centreFederal environmental registers
- San Mar's boundary and the 298 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~225-day seasonGrowable Ground crop-matching engine
- The ecoregion at San Mar's own centroid, the Ridge and ValleyUS EPA Level III Ecoregions
- A documented spotted-lanternfly record within reach of San Marlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so San Mar's 298 acres read through its county's SSURGO summaryfrom Washington County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Washington County
- The growing challenges every Maryland grower plans around — written at state scale, so they stay on the state guidefrom Maryland
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Washington County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among San Mar's 298 acreswhy one lot differs from the next →
- Which side of San Mar you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 298 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.1 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 San Mar-wide figureread your own land →