What USDA hardiness zone is Decatur County, Iowa?

Every ZIP code in Decatur County, Iowa is USDA hardiness zone 5b, from the USDA 2023 Plant Hardiness Zone Map.

When is the last spring frost in Decatur County, Iowa?

The median last spring freeze runs April 16 – April 30 across the 5 NOAA weather stations serving Decatur County, Iowa, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Iowa

Planting zones in Decatur County, Iowa

Every ZIP code in this county is USDA zone 5b — so unlike most of the places people look up, there is one right answer here and it holds wherever you are in the county.

USDA zone 5b The same in all 7 ZIP codes

ZIP codes 7 7 have a NOAA station within range

Weather stations 5 NOAA 1991–2020 normals, across 532 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Decatur County, Iowa as a whole. Hardiness zones and freeze dates are published per ZIP code, so yours is exact — enter it and this page will tell you your zone, which NOAA station it comes from and how far away that station is.

The growing season in Decatur County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives October 8 – October 21 across the 5 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around February 19 – March 5 — counted back from a last spring freeze of April 16 – April 30 here.

Every spring date for your ZIP →

These are ranges across the whole county. The ZIP lookup above gives the dates from your own nearest station instead.

All 5 stations agreeAt least one station

Every one of the 5 NOAA stations serving this county counts April 30 – October 8 as growing season (161 days). Widening to any single station gives April 16 – October 21 (188 days).

That is a 27-day difference inside one county — which is why this page gives ranges rather than a single planting date. The ZIP lookup above resolves it to one station.

Your freeze dates

Last spring freeze April 16 – April 30

First fall freeze October 8 – October 21

Across the 5 NOAA stations serving this county. These are medians — half of years freeze later than the date shown — so treat the later end of each range as the cautious one.

The growing season runs 161–187 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 81.7–84.5 °F in June–August. Summer rain over the same months runs 13.3–14.5" across those 4 stations, against the rough inch a week — about 13 inches over the same 92 days — that a vegetable garden is usually reckoned to want. At the middle station that is covered, so watering in Decatur County is for the gaps between storms rather than the whole season. The inches are NOAA's published normals; the inch a week is a rule of thumb, and it takes no account of a 84 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Decatur County

Zones are published per ZIP code, not per county, so this is the exact answer rather than the county's average. The station column is the nearest one to that ZIP code's centroid and how far away it is — the same figure the tools use, shown here so you can see which ZIP codes are well covered and which are reaching.

ZIP code	USDA zone	Nearest NOAA station	Distance
50065	5b	Lamoni Muni AP, IA	11.0 km
50067	5b	Lamoni Muni AP, IA	6.8 km
50103	5b	Leon 6 Ese, IA	8.4 km
50108	5b	Beaconsfield, IA	7.2 km
50140	5b	Lamoni, IA	1.9 km
50144	5b	Leon 6 Ese, IA	7.8 km
50262	5b	Osceola, IA	18.4 km

ZIP-code positions are area centroids, so a large rural ZIP code's listed distance is measured from the middle of its area rather than from any particular address in it.

When to start seeds in Decatur County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 5 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	February 19 – March 5	8 wk before
🌶️ Peppers	Start indoors	February 19 – March 5	8 wk before
🥦 Broccoli	Start indoors	March 5 – March 19	6 wk before
🥬 Cabbage	Start indoors	March 5 – March 19	6 wk before
🥬 Collards	Start indoors	March 5 – March 19	6 wk before
🥬 Kale	Start indoors	March 5 – March 19	6 wk before
🥬 Leaf Lettuce	Start indoors	March 5 – March 19	6 wk before
🫛 Peas	Direct sow	March 5 – March 19	6 wk before
🥬 Spinach	Direct sow	March 5 – March 19	6 wk before
🍠 Sweet Potato	Start indoors	March 5 – March 19	6 wk before
🍅 Tomatoes	Start indoors	March 5 – March 19	6 wk before
🥬 Bok Choy	Start indoors	March 12 – March 26	5 wk before
🥬 Kohlrabi	Start indoors	March 12 – March 26	5 wk before
🥬 Swiss Chard	Start indoors	March 12 – March 26	5 wk before
🥬 Arugula	Direct sow	March 19 – April 2	4 wk before
🥬 Baby Salad Greens	Direct sow	March 19 – April 2	4 wk before
🥕 Beets	Direct sow	March 19 – April 2	4 wk before
🧅 Green Onions	Direct sow	March 19 – April 2	4 wk before
🥬 Mustard Greens	Direct sow	March 19 – April 2	4 wk before
🌶️ Okra	Start indoors	March 19 – April 2	4 wk before
🌱 Radishes	Direct sow	March 19 – April 2	4 wk before
🥔 Turnips	Direct sow	March 19 – April 2	4 wk before
🥬 Cabbage	Set out	March 26 – April 9	3 wk before
🥕 Carrots	Direct sow	March 26 – April 9	3 wk before
🥬 Collards	Direct sow	March 26 – April 9	3 wk before
🥬 Collards	Set out	March 26 – April 9	3 wk before
🥒 Cucumbers	Start indoors	March 26 – April 9	3 wk before
🧅 Green Onions	Set out	March 26 – April 9	3 wk before
🥬 Kale	Direct sow	March 26 – April 9	3 wk before
🥬 Kale	Set out	March 26 – April 9	3 wk before
🥬 Kohlrabi	Direct sow	March 26 – April 9	3 wk before
🥬 Kohlrabi	Set out	March 26 – April 9	3 wk before
🥬 Leaf Lettuce	Direct sow	March 26 – April 9	3 wk before
🎃 Pumpkins	Start indoors	March 26 – April 9	3 wk before
🎃 Summer Squash	Start indoors	March 26 – April 9	3 wk before
🎃 Winter Squash	Start indoors	March 26 – April 9	3 wk before
🥒 Zucchini	Start indoors	March 26 – April 9	3 wk before
🥬 Bok Choy	Direct sow	April 2 – April 16	2 wk before
🥬 Bok Choy	Set out	April 2 – April 16	2 wk before
🥦 Broccoli	Set out	April 2 – April 16	2 wk before
🌿 Cilantro	Direct sow	April 2 – April 16	2 wk before
🥬 Leaf Lettuce	Set out	April 2 – April 16	2 wk before
🥬 Swiss Chard	Direct sow	April 2 – April 16	2 wk before
🥬 Swiss Chard	Set out	April 2 – April 16	2 wk before
🌿 Dill	Direct sow	April 9 – April 23	1 wk before
🫘 Bush Beans	Direct sow	April 23 – May 7	1 wk after
🥒 Cucumbers	Set out	April 23 – May 7	1 wk after
🎃 Pumpkins	Direct sow	April 23 – May 7	1 wk after
🎃 Pumpkins	Set out	April 23 – May 7	1 wk after
🎃 Summer Squash	Direct sow	April 23 – May 7	1 wk after
🎃 Summer Squash	Set out	April 23 – May 7	1 wk after
🌽 Sweet Corn	Direct sow	April 23 – May 7	1 wk after
🍅 Tomatoes	Set out	April 23 – May 7	1 wk after
🎃 Winter Squash	Direct sow	April 23 – May 7	1 wk after
🎃 Winter Squash	Set out	April 23 – May 7	1 wk after
🥒 Zucchini	Direct sow	April 23 – May 7	1 wk after
🥒 Zucchini	Set out	April 23 – May 7	1 wk after
🥒 Cucumbers	Direct sow	April 30 – May 14	2 wk after
🌶️ Okra	Direct sow	April 30 – May 14	2 wk after
🌶️ Okra	Set out	April 30 – May 14	2 wk after
🌶️ Peppers	Set out	April 30 – May 14	2 wk after
🫘 Southern Peas	Direct sow	April 30 – May 14	2 wk after
🍠 Sweet Potato	Set out	April 30 – May 14	2 wk after

Offsets are published guidance; the dates they land on are computed from measured NOAA normals. The seed-starting tool does this for your own ZIP code and counts the days.

What lives through a zone 5b winter

Of 74 perennial edibles, 48 come through a zone 5b winter — and 0 fail here for being too warm rather than too cold, needing more winter chill than this county gets or more heat than they tolerate. Among the ones that work: Cranberry, Honeyberry, Lingonberry, Apple, Aronia, Black Currant, Elderberry, Gooseberry.

Hardiness ranges are a judgement, published by growers rather than measured; the zone they are compared against is measured. On a warm-end verdict, check with your local extension service — a coastal zone 8 and an inland zone 8 are not the same summer.

Cautious — shortens the seasonMedian across stationsOptimistic

Last spring freeze: Plan to May 15 to be careful. Median April 16 – April 30 across 5 stations; April 2 is the optimistic end.
First fall freeze: Plan to September 24 to be careful. Median October 8 – October 21 across 5 stations; November 1 is the optimistic end.

NOAA publishes these as probabilities, not averages — the middle figure is a median, so half of years fall either side of it. The cautious end is the 10% tail: in roughly nine years in ten the freeze falls on the safe side of it.

The 5 stations behind these numbers

All 5 NOAA stations whose normals this page quotes, spanning about 43 km north to south. Every one is named with its identifier in the station list below — this page does not single one out, because no one station speaks for a whole county.

A relative sketch, not a map with a projection: longitude is adjusted for latitude so the shape is not stretched, and there is no basemap. For the one station nearest a specific address, with its real distance, use the ZIP lookup above.

These are the stations this county's ZIP codes actually cite as nearest — not a claim that each one sits inside its boundary, since a rural ZIP legitimately reaches over it. Every figure above comes from them, and each is named so you can check it.

Station	NOAA ID	Last spring freeze	First fall freeze	Season
Beaconsfield, IA	USC00130536	April 23	October 17	176 days
Lamoni Muni AP, IA	USW00094991	April 16	October 21	186 days
Lamoni, IA	USW00014993	April 16	October 20	187 days
Leon 6 Ese, IA	USC00134758	April 30	October 8	161 days
Osceola, IA	USC00136316	April 29	October 9	162 days

These are medians, not averages — NOAA publishes freeze dates as a probability distribution, and half of years freeze later than the date shown.

Your own ZIP

Work out your own dates

This page describes a whole county. Every tool below answers for one ZIP code, which is the grain the underlying data is published at.

Other places to compare

Decatur County sits in Iowa. That page carries the whole state's zone spread, its metro areas, and every other county in it with a page here.

More of Iowa

Counties with the same zones — 5b

Matched on the exact zone set, not a dominant zone, so the winter answer on these pages really is the same one as here.

Gear

If you want to act on this

Each link opens an Amazon search rather than a product we picked. We have not tested these and do not rank them — the search is the honest version, and you choose.

Trunk wrapZone 5b is cold enough that winter sun on a young trunk does more damage than the cold does.
Row cover and frost clothThe season here closes at the first fall freeze dated above — a cover buys back some of those days at the end.
MulchFor the perennials nearest their cold limit in zone 5b, where an insulated crown is what decides whether they come back.

As an Amazon Associate we earn from qualifying purchases. That costs you nothing extra, and it buys no influence over anything on this site: the dates come from NOAA normals and the zones from the USDA, and no product affects either.

Sources

Where these numbers come from

Hardiness zones are the USDA 2023 Plant Hardiness Zone Map, published per ZIP code by PRISM at Oregon State. Freeze dates and growing-season lengths are NOAA 1991–2020 Climate Normals, taken per station and cited above by name and NOAA ID.

County boundaries come from the Census ZCTA-to-county relation, which is what places each ZIP code — and which treats parishes, boroughs and census areas as county equivalents. No station is chosen to represent this county: every range above is taken across all of them and the count is stated, because picking one would be a judgement dressed as a measurement.