What do the a and b in a planting zone mean?

Each USDA zone is a 10°F band of winter low temperature. The 'a' half is the colder 5°F and the 'b' half the warmer 5°F; for example zone 7a is 0 to 5°F and zone 7b is 5 to 10°F.

Does my planting zone tell me when to plant?

Not on its own. The zone says which perennials survive your winter. Planting dates come from your average last spring frost and first fall frost, which WhenPlant reads from your nearest NOAA weather station.

What planting zone am I in — and what can I plant now?

Q: What planting zone am I in?

Your planting zone is your USDA plant hardiness zone, set by the coldest night of an average winter (average annual extreme minimum temperature, 1991-2020) on the USDA 2023 map. Enter your ZIP code on WhenPlant to get your zone and your local frost dates.

Enter your ZIP code. WhenPlant finds your USDA hardiness zone and real local frost dates, then tells you exactly what to sow, start, and transplant this month — for every crop.

Free. No sign-up. Your zone comes from the USDA 2023 map; frost dates from your nearest NOAA weather station (1991–2020 normals).

What planting zone am I in?

Your planting zone is your USDA hardiness zone: enter your ZIP above to get it. Most of the US falls between zone 3 and zone 10. The zone comes from the coldest night of an average winter (USDA 2023 map, 1991–2020); each zone is a 10°F band, with “a” the colder and “b” the warmer 5°F half. It tells you which perennials survive winter. When to plant depends on your frost dates.

Show the winter low and frost dates for each zone

Tap a zone for its full planting calendar.
Zone	Winter low	Last frost	First frost
2a	−50 to −45°F	~05/17	~09/07
2b	−45 to −40°F	~05/25	~09/15
3b	−35 to −30°F	~05/20	~09/19
4a	−30 to −25°F	~05/14	~09/27
4b	−25 to −20°F	~05/10	~09/30
5a	−20 to −15°F	~05/12	~10/01
5b	−15 to −10°F	~05/04	~10/08
6a	−10 to −5°F	~04/30	~10/15
6b	−5 to 0°F	~04/23	~10/20
7a	0 to 5°F	~04/15	~10/26
7b	5 to 10°F	~04/06	~11/01
8a	10 to 15°F	~03/26	~11/08
8b	15 to 20°F	~03/16	~11/15
9a	20 to 25°F	~03/02	~11/25
9b	25 to 30°F	~02/02	~12/11
10a	30 to 35°F	~01/11	~12/31
10b	35 to 40°F	~01/13	~01/09

Winter low: USDA ARS 2023 Plant Hardiness Zone Map definition (average annual extreme minimum temperature, 1991–2020). Frost dates: median of the NOAA stations in each zone (1991–2020 normals, 50% chance of 32°F). Zones with fewer than three NOAA frost stations in our data are not listed (such as 1b and 3a). A zone with few stations can sit slightly out of order with its neighbour, and your own station can differ by weeks, so use the ZIP tool for your dates.

What to plant in November

These crops have a planting window this month in at least one of the 17 zones. Enter your ZIP above to see which apply where you live.

GarlicPlant cloves (harvest next summer) · in 7 of 17 zones CabbageStart indoors · in 3 of 17 zones KaleStart indoors · in 3 of 17 zones RadishesSow for fall harvest · in 3 of 17 zones CollardsStart indoors · in 3 of 17 zones CeleryStart indoors · in 3 of 17 zones

Between planting windows in November

In these 7 zones nothing on our list has a planting window this month. The date is when the next one opens; tap your zone to see what to start then.

Next window opens

Browse by hardiness zone

Zone 4bLast frost ~05/10 · first ~09/30 Zone 5bLast frost ~05/04 · first ~10/08 Zone 6bLast frost ~04/23 · first ~10/20 Zone 7aLast frost ~04/15 · first ~10/26 Zone 8aLast frost ~03/26 · first ~11/08 Zone 9aLast frost ~03/02 · first ~11/25

See all 17 zones →

Supplies for November planting

Picked for the crops on this month's list (Garlic, Cabbage, Kale and more). Enter your ZIP above to see which of them fit your zone, reuse what you already have, and check sizes before ordering.

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How WhenPlant works

1 · Your zone

Your ZIP maps to a USDA 2023 hardiness zone — the standard measure of how cold your winters get.

2 · Your frost dates

We pull your nearest NOAA station's 1991–2020 average last-spring and first-fall frost — the two dates the whole calendar counts from.

3 · Your calendar

Every crop's cited planting rule is computed against your dates: when to start indoors, transplant, direct-sow, and sow for fall.

Read the full methodology & sources →