Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 21837 — Mardela Springs, MD

ZIP code 21837 (Mardela Springs, Wicomico County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 8 and the first fall frost November 4.

Where ZIP 21837 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone7b5 to 10 °F
Coldest night−15 to −12.2 °C
Last frostApr 8
First frostNov 4
2012 zone7b

Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 7b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mardela Springs, MD…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Mardela Springs, MD

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 8median — 50% chance of a later frost
Safe for tender plantsApril 23only 10% chance of frost after
First fall frostNovember 4median — 10% chance by Oct 22
Growing season209 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 27 and returns around November 17.

From the NOAA station Vienna, MD — 4 miles away, elevation 10 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 21837

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 25 – Mar 11
SpinachSow outdoors · Feb 25 – Mar 18
Broccoli, cabbageStart indoors · Jan 28 – Feb 11
Broccoli, cabbageTransplant · Mar 18 – Apr 1
Onion setsPlant outdoors · Mar 11 – Mar 25
PotatoesPlant outdoors · Mar 18 – Apr 1
LettuceSow outdoors · Mar 11 – Mar 25
Carrots, beetsSow outdoors · Mar 18 – Apr 1
TomatoesStart indoors · Feb 11 – Feb 25
TomatoesTransplant · Apr 15 – Apr 29
Peppers, eggplantStart indoors · Jan 28 – Feb 11
Peppers, eggplantTransplant · Apr 22 – May 6
BeansSow outdoors · Apr 15 – Apr 29
Sweet cornSow outdoors · Apr 15 – Apr 29
Cucumbers, squashSow outdoors · Apr 15 – Apr 29
Fall lettuce, spinachSow outdoors · Sep 9 – Sep 23
GarlicPlant cloves · Oct 21 – Nov 25
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 8) and first fall frost (Nov 4) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 21837 came on Mar 10 — 3 days later than the 1991–2020 average (Mar 7).

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 7b in Maryland

618 plants native to the lower 48 states, recorded in Maryland, and rated by the USDA to survive 5 °F or colder — the bottom of zone 7b. Each links to its USDA PLANTS profile.

Trees 83

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican chestnut115 ft · blooms early summer · high shade tolerance · to −33 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °F

Shrubs 127

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican beautyberry6 ft · blooms early summer · medium shade tolerance · to −8 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °F

Wildflowers & perennials 206

American bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °FAmerican speedwell0.8 ft · blooms mid summer · low shade tolerance · to −38 °FAmerican spongeplant0.5 ft · blooms mid spring · high shade tolerance · to −24 °F

Grasses 176

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °FAmerican cupscale3 ft · blooms early summer · high shade tolerance · to −18 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °FAtlantic mannagrass3 ft · blooms summer · low shade tolerance · to −8 °Fautumn bluegrass1.5 ft · blooms late spring · medium shade tolerance · to −8 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °F

Vines 12

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °FAmerican wisteria50 ft · blooms spring · low shade tolerance · to −3 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Fgraybark grape50 ft · blooms late spring · medium shade tolerance · to −8 °Fheartleaf peppervine2 ft · blooms late spring · low shade tolerance · to −8 °F

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Mardela Springs, MD.

Soil in Mardela Springs, MD

The soil mapped at the center of ZIP 21837 is Hambrook — sandy loam, well drained.

TextureSandy loamdrains and warms fast; dries out and needs more feeding
pH6.0slightly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.5%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classprime farmlandUSDA classification

Map unit: Hambrook sandy loam, 2 to 5 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 21837; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mardela Springs, MD

Summer high90 °Faverage high, July
Winter low28 °Faverage low, January
Hot days43days a year at 90 °F or more
Freezing nights83nights a year at 32 °F or less
Growing degree days4,375base 50 °F — the season’s usable heat
Longest day14 h 51 mindaylight on June 21
Shortest day9 h 29 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation49.9 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 48 °F, low 28 °F 48°28° JanFebruary: average high 50 °F, low 29 °F 50°29° FebMarch: average high 58 °F, low 36 °F 58°36° MarApril: average high 69 °F, low 44 °F 69°44° AprMay: average high 78 °F, low 54 °F 78°54° MayJune: average high 86 °F, low 63 °F 86°63° JunJuly: average high 90 °F, low 69 °F 90°69° JulAugust: average high 88 °F, low 67 °F 88°67° AugSeptember: average high 82 °F, low 61 °F 82°61° SepOctober: average high 72 °F, low 49 °F 72°49° OctNovember: average high 61 °F, low 39 °F 61°39° NovDecember: average high 51 °F, low 31 °F 51°31° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 3.51 in precipitation 3.5 JanFebruary: 3.08 in precipitation 3.1 FebMarch: 4.43 in precipitation 4.4 MarApril: 3.63 in precipitation 3.6 AprMay: 4.00 in precipitation 4.0 MayJune: 4.53 in precipitation 4.5 JunJuly: 4.66 in precipitation 4.7 JulAugust: 5.04 in precipitation 5.0 AugSeptember: 5.36 in precipitation 5.4 SepOctober: 4.40 in precipitation 4.4 OctNovember: 3.35 in precipitation 3.4 NovDecember: 3.92 in precipitation 3.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Vienna, MD (4 mi away); precipitation: Salisbury 2n, MD (10 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7b.

218307b
Hebron, MD · 4 mi
218617b
Sharptown, MD · 6 mi
216597b
Rhodesdale, MD · 9 mi
218017b
Salisbury, MD · 9 mi
218567b
Quantico, MD · 9 mi
218027b
Salisbury, MD · 9 mi
218037b
Salisbury, MD · 9 mi
218697b
Vienna, MD · 9 mi

Maryland planting zones →

Questions about 21837

What planting zone is ZIP code 21837?

ZIP code 21837 (Mardela Springs, MD) is in USDA hardiness zone 7b on the 2023 map: the coldest night of an average winter reaches 5 to 10 °F (−15 to −12.2 °C).

When is the last frost in Mardela Springs, MD?

The median last spring frost (32 °F) near 21837 is April 8; after April 23 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Vienna station.

When is the first frost in Mardela Springs, MD?

The median first fall frost near 21837 is November 4, giving a median frost-free growing season of 209 days.

When should I plant tomatoes in 21837?

Start tomato seeds indoors around Feb 11 – Feb 25 and set transplants outside around Apr 15 – Apr 29, one to three weeks after the median last frost.

How much rain and snow does 21837 get?

About 49.9 inches of precipitation a year (NOAA 1991–2020 normals, Salisbury 2n station).

How hot do summers get in Mardela Springs, MD?

The average high peaks at 90 °F in July, with about 43 days a year at 90 °F or more.

What kind of soil does 21837 have?

The USDA soil survey maps Hambrook at the center of ZIP 21837: sandy loam, well drained, pH about 6.0 (slightly acidic).

Did spring come early in Mardela Springs, MD in 2026?

Spring leaf-out near 21837 came on Mar 10 in 2026, 3 days later than the 1991–2020 average (Mar 7), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mardela Springs, MD?

Intermediate onions: the longest day near 21837 is 14 h 51 min, so day-neutral types bulb best; long-day varieties may not bulb fully.