What does USDA hardiness zone 6b mean in Maryland?

Zone 6b means an average annual extreme minimum winter temperature of −5 to 0 °F — the standard USDA measure of which perennials survive winter. 1 location in Maryland fall in this zone. It does not set planting dates; see the frost calendar below for that.

When should I plant tomatoes in Maryland's zone 6b?

Using Bloomington's frost dates (this page's median-season location): start seeds indoors about Mar 4 – Mar 18, then transplant outside about May 6 – May 13. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.

Does every location in Maryland's zone 6b have the same frost dates?

No — they do not all share a weather station, so frost dates vary by a week or more across the 1 locations listed (see the table above for each location's own dates).

USDA zone 6b in Maryland

−5 to 0 °F avg. annual extreme minimum · 1 location in this group · NOAA 1991–2020 normals

USDA plant hardiness zone 6b covers 1 location across Maryland (average annual extreme minimum −5 to 0 °F): Bloomington, MD. Average last spring frost across this group ranges April 29 and growing seasons run 174 days — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Maryland location's own frost dates; the printable planting calendar uses Bloomington, this group's median-season location.

USDA zone: 6b−5 to 0 °F
Last frost range: Apr 29avg, 32°F
First frost range: Oct 20avg, 32°F
Growing season range: 174days

Locations in this group

Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.

Own frost dates per location.
Location	Also covers	Nearest station	Last frost	First frost	Season (days)
Bloomington *	Franklin, Barton	Savage Rvr Dam	Apr 29	Oct 20	174

* Bloomington is this group's median-season location — the calendar below is computed from its data.

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.

Planting calendar (Bloomington, representative)

Computed from Bloomington's average frost dates — the median-season location in this Marylandzone 6b group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).

Crop

JanFebMarAprMayJunJulAugSepOctNovDec

Tomato

Pepper

Cucumber

Summer squash / zucchini

Start indoors
Plant out
Fall sowing
First harvest

Planting windows for Bloomington (Maryland, zone 6b), this group's representative location.
Crop	Frost tolerance	Start indoors	Plant out	First harvest	Fall planting	Season fit
Tomato	Tender	Mar 4 – Mar 18	May 6 – May 13	Jul 5 – Jul 25	—	matures comfortably
Pepper	Very tender	Feb 18 – Mar 4	May 13 – May 20	Jul 12 – Aug 11	—	matures comfortably
Cucumber	Tender	Apr 1 – Apr 8	May 6 – May 13	Jun 25 – Jul 15	—	matures comfortably
Summer squash / zucchini	Tender	—	May 6 – May 13	Jun 20 – Jul 5	—	matures comfortably
Bush bean	Tender	—	May 6 – May 13	Jun 25 – Jul 5	Aug 21 – Aug 31	matures comfortably
Sweet corn	Tender	—	Apr 29 – May 13	Jun 28 – Jul 28	—	matures comfortably
Basil	Very tender	Mar 18 – Apr 1	May 6 – May 13	Jun 5 – Jun 20	—	matures comfortably
Lettuce	Half-hardy	Mar 18 – Apr 1	Apr 1 – Apr 15	May 16 – May 31	Aug 7 – Aug 22	matures comfortably
Pea	Hardy	—	Mar 18 – Apr 1	May 12 – May 27	Jul 28 – Aug 12	matures comfortably
Spinach	Hardy	—	Mar 18 – Apr 1	Apr 27 – May 7	Aug 17 – Aug 27	matures comfortably
Carrot	Half-hardy	—	Apr 8 – Apr 15	Jun 7 – Jun 27	Jul 18 – Aug 7	matures comfortably
Broccoli	Half-hardy	Mar 4 – Mar 18	Apr 1 – Apr 15	May 26 – Jun 15	Jul 23 – Aug 12	matures comfortably

Which crops fit this growing season

Using Bloomington's own 174-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.

Frost & freeze dates (Bloomington)

From NOAA's 1991–2020 Climate Normals at station USC00188065. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.

Freeze probabilities by temperature threshold (MM/DD, NOAA 1991–2020), Bloomington.
Threshold	Last spring — avg	Last spring — 90%-safe	First fall — avg	First fall — 90%-safe	Season (days)
36°F	May 8	May 24	Oct 6	Oct 21	150
32°F (freeze)	Apr 29	May 15	Oct 20	Nov 2	174
28°F	Apr 12	May 1	Nov 1	Nov 15	203
24°F	Mar 31	Apr 12	Nov 12	Nov 30	226

Growing degree days

Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 1 locations is 2,642; Bloomington's own reading is shown below.

Annual growing degree days for Bloomington (°F·days, NOAA 1991–2020).
Model	°F·days	Used for
Base 50°F (warm-season)	2,642	standard warm-season base (tomato, corn, beans)
Base 40°F (cool-season)	4,828	cool-season crops (brassicas, greens)

Hardiness zone 6b in Maryland

Zone 6b means an average annual extreme minimum winter temperature of about −5 to 0 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Maryland spans 5 hardiness zones in this dataset — see all Maryland locations for the full range, including zones6a, 7a, 7b, 8a.

Explore zone 6b in other states at zone 6b, or see all USDA hardiness zones.

Frequently asked questions

What does USDA hardiness zone 6b mean in Maryland?: Zone 6b means an average annual extreme minimum winter temperature of −5 to 0 °F — the standard USDA measure of which perennials survive winter. 1 location in Maryland fall in this zone. It does not set planting dates; see the frost calendar below for that.
When should I plant tomatoes in Maryland's zone 6b?: Using Bloomington's frost dates (this page's median-season location): start seeds indoors about Mar 4 – Mar 18, then transplant outside about May 6 – May 13. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
Does every location in Maryland's zone 6b have the same frost dates?: No — they do not all share a weather station, so frost dates vary by a week or more across the 1 locations listed (see the table above for each location's own dates).

Sources & method

Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.