When to Plant in Iowa: Vegetable & Flower Planting Calendar
Quick answer
Plant around your local last spring frost: across the 970 Iowa ZIP codes where frost comes in most years, the median is Apr 28 and the median first fall frost is Oct 10 (nearest NOAA station, 1991–2020). Transplant tomatoes 1–2 weeks after your last frost: Zone 5 areas: May 5 – May 12.
Iowa spans USDA hardiness zones 4b–6a on the 2023 USDA map (by ZIP code, via PRISM). For the 970 of its 970 ZIP codes where frost comes in most years, the nearest NOAA station’s median last spring frost (32°F, 1991–2020) is Apr 28 (middle 80% of ZIP codes: Apr 20 – May 3) and the median first fall frost is Oct 10 (Oct 3 – Oct 19). Use this guide to time seed-starting, transplanting and fall planting.
Where these dates come from: every date range is counted from the median (50% probability) 32°F last spring and first fall frost dates in NOAA’s 1991–2020 U.S. Climate Normals for the area shown. The rule under each date, such as “4–6 weeks before last frost,” shows how it was counted. These are averages: in about half of years a frost still comes after the spring date, and elevation, nearby water and microclimate can shift your yard by a week or more. For dates for your exact location, enter your ZIP code in the planner.
How we count planting dates: the weeks before or after frost for each crop come from university extension planting guides: UNH Extension, When to Plant Your Vegetable Garden; Rutgers FS787, Starting Vegetable Seeds Indoors; Virginia Tech 426-331, Home Garden Vegetable Planting Guide; University of Maryland Extension, Vegetable Planting Calendar; and University of Idaho CIS 1209 (marigolds and zinnias). Bulb windows approximate Rutgers’ rule to plant when soil falls below 60°F (FS1220), and garlic follows SDSU, Illinois and Virginia Tech. Temperature notes: UMD (potatoes), UMN (sweet corn), UC ANR (peppers, hardening off), UMN (eggplant), Colorado State (tomatoes) and SDSU (hardening off).
Iowa frost dates by zone area
| Zone areas | Most common nearest NOAA stations | Median last spring frost (32°F) | Median first fall frost (32°F) |
|---|---|---|---|
| Zone 5 (918 ZIP codes) | Des Moines Intl Airport, IA, Waterloo Muni Airport, IA, Sigourney, IA | Apr 28middle 80%: Apr 20 – May 3 | Oct 10middle 80%: Oct 3 – Oct 18 |
Source: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991–2020, annual/seasonal freeze-date probabilities (32°F, 50% probability). Station-level medians; your yard may differ.
How this table is built: each Iowa ZIP code is matched to its nearest NOAA 1991–2020 freeze-data station (within 60 miles) and grouped by its 2023 USDA hardiness zone; dates are medians across the ZIP codes in each group. Zone groups with fewer than 5% of ZIP codes (44 ZIP codes) are left out of the columns. Some nearest stations are across the state line (Blair, NE, Canton, SD, Fulton L&D #13, IL, Galena, IL, Genoa Dam 8, WI, Gladstone Dam 18, IL…). For your own ZIP, use the planner.
Iowa vegetable planting calendar
Planting dates for each zone area of Iowa, counted from that area’s median frost dates (shown under each column). Rows run in calendar order. For your exact dates, enter your ZIP.
| Plant | Task | Dates (and how they are counted) | Expected harvest (estimate) |
|---|---|---|---|
| Broccoli | Start indoors | Feb 17 – Mar 38–10 weeks before last frost (avg. Apr 28) | — |
| Cabbage | Start indoors | Feb 17 – Mar 38–10 weeks before last frost (avg. Apr 28) | — |
| Kale | Start indoors | Feb 17 – Mar 38–10 weeks before last frost (avg. Apr 28) | — |
| Tomatoes | Start indoors | Mar 3 – Mar 176–8 weeks before last frost (avg. Apr 28) | — |
| Peppers | Start indoors | Mar 3 – Mar 176–8 weeks before last frost (avg. Apr 28) | — |
| Eggplant | Start indoors | Mar 3 – Mar 176–8 weeks before last frost (avg. Apr 28) | — |
| Peas | Direct sow | Mar 17 – Mar 314–6 weeks before last frost (avg. Apr 28) | May 16 – Jun 1960–80 days from seeding |
| Spinach | Direct sow | Mar 17 – Mar 314–6 weeks before last frost (avg. Apr 28) | May 1 – May 3045–60 days from seeding |
| Basil | Start indoors | Mar 17 – Mar 314–6 weeks before last frost (avg. Apr 28) | — |
| Radishes | Direct sow | Mar 24 – Apr 142–5 weeks before last frost (avg. Apr 28) | Apr 13 – May 1420–30 days from seeding |
| Lettuce | Direct sow | Mar 31 – Apr 142–4 weeks before last frost (avg. Apr 28) | May 30 – Jul 360–80 days from seeding |
| Onions (sets/transplants) | Plant sets/transplants | Mar 31 – Apr 142–4 weeks before last frost (avg. Apr 28) | Jun 24 – Aug 1285–120 days from planting |
| Broccoli | Transplant | Mar 31 – Apr 142–4 weeks before last frost (avg. Apr 28) | May 20 – Jun 2350–70 days from transplanting |
| Cabbage | Transplant | Mar 31 – Apr 142–4 weeks before last frost (avg. Apr 28) | Jun 9 – Jul 1370–90 days from transplanting |
| Kale | Transplant | Mar 31 – Apr 142–4 weeks before last frost (avg. Apr 28) | — |
| Marigolds | Start indoors | Apr 7 – Apr 280–3 weeks before last frost (3–4 weeks before setting out; Univ. of Idaho) (avg. Apr 28) | — |
| Zinnias | Start indoors | Apr 7 – Apr 280–3 weeks before last frost (3–4 weeks before setting out; Univ. of Idaho) (avg. Apr 28) | — |
| Potatoes | Plant seed potatoes | Apr 14 – Apr 211–2 weeks before last frost (avg. Apr 28) | Jul 8 – Aug 985–110 days from planting |
| Marigolds | Direct sow / transplant | Apr 28 – May 12from the last frost to 2 weeks after (Univ. of Idaho) (avg. Apr 28) | — |
| Zinnias | Direct sow / transplant | Apr 28 – May 12from the last frost to 2 weeks after (Univ. of Idaho) (avg. Apr 28) | — |
| Tomatoes | Transplant | May 5 – May 121–2 weeks after last frost (avg. Apr 28) | Jul 14 – Aug 1070–90 days from transplanting |
| Beans (bush & pole) | Direct sow | May 5 – May 121–2 weeks after last frost (avg. Apr 28) | Jun 19 – Jul 2145–70 days from seeding |
| Sweet corn | Direct sow | May 5 – May 121–2 weeks after last frost (avg. Apr 28) | Jul 9 – Aug 1065–90 days from seeding |
| Cucumbers | Direct sow | May 5 – May 121–2 weeks after last frost (avg. Apr 28) | Jun 14 – Jul 1640–65 days from seeding |
| Squash | Direct sow | May 5 – May 121–2 weeks after last frost (avg. Apr 28) | Jun 14 – Jul 140–50 days from seeding |
| Pumpkins | Direct sow | May 5 – May 191–3 weeks after last frost (avg. Apr 28) | Jul 24 – Aug 2780–100 days from seeding |
| Basil | Transplant | May 5 – May 121–2 weeks after last frost (avg. Apr 28) | Jun 16 – Jun 2342 days from transplanting |
| Peppers | Transplant | May 12 – May 192–3 weeks after last frost (avg. Apr 28) | Jul 16 – Aug 265–75 days from transplanting |
| Eggplant | Transplant | May 12 – May 192–3 weeks after last frost (avg. Apr 28) | Jul 21 – Aug 1770–90 days from transplanting |
| Broccoli | Fall transplant | Jul 18 – Aug 110–12 weeks before first fall frost (avg. Oct 10) | Sep 6 – Oct 1050–70 days from transplanting |
| Cabbage | Fall transplant | Jul 18 – Aug 110–12 weeks before first fall frost (avg. Oct 10) | Sep 26 – Oct 3070–90 days from transplanting |
| Kale | Fall sow | Aug 1 – Aug 158–10 weeks before first fall frost (avg. Oct 10) | Sep 20 – Oct 2450–70 days from seeding |
| Lettuce | Fall sow | Aug 15 – Aug 296–8 weeks before first fall frost (avg. Oct 10) | Oct 14 – Nov 1760–80 days from seeding |
| Spinach | Fall sow | Aug 22 – Sep 124–7 weeks before first fall frost (Virginia Tech) (avg. Oct 10) | Oct 6 – Nov 1145–60 days from seeding |
| Radishes | Fall sow | Aug 29 – Sep 124–6 weeks before first fall frost (avg. Oct 10) | Sep 18 – Oct 1220–30 days from seeding |
| Daffodils | Fall plant bulbs | Sep 12 – Oct 244 weeks before to 2 weeks after first fall frost (our approximation of when soil falls below 60°F; Rutgers) (avg. Oct 10) | — |
| Tulips | Fall plant bulbs | Sep 26 – Nov 72 weeks before to 4 weeks after first fall frost (our approximation of when soil falls below 60°F; Rutgers) (avg. Oct 10) | — |
| Garlic | Fall plant cloves | Sep 26 – Oct 312 weeks before to 3 weeks after first fall frost, while the soil is still workable (SDSU, Illinois, Virginia Tech) (avg. Oct 10) | Jun 3, 2027 – Jul 28, 2027250–270 days from planting |
About the harvest estimates
Each expected harvest window adds the days to harvest from the sources below to the planting window. Days count from sowing seed (or planting seed potatoes, onion sets or garlic cloves) or, where marked, from setting transplants out; “Start indoors” rows have no harvest of their own. Harvest timing varies with variety and weather, and many crops keep producing for weeks after the first picking. For frost-tender crops (tomatoes, peppers, eggplant, beans, sweet corn, cucumbers, squash, pumpkins, basil) the window stops at the first fall frost: harvest may end early at the first fall frost. Flowers and bulbs show no harvest window, and kale has no sourced figure for spring transplants.
Sources: UF/IFAS Extension, Florida Vegetable Gardening Guide (SP103/VH021), Table 1, “Days to Harvest”; University of Maryland Extension, Growing Onions in a Home Garden; University of Maryland Extension, Growing Garlic in a Home Garden; University of Maryland Extension, Growing Basil in a Home Garden.
Growing notes for each crop
- Peas: Tolerates light frost; sow when soil is workable
- Spinach: Fall crop too: sow 4–7 weeks before first fall frost (Virginia Tech)
- Lettuce: Bolts in heat; succession sow; fall crop too
- Radishes: Fast (3–4 weeks); sow again for fall (see Fall sow dates)
- Kale: Fall crop too (see Fall sow dates); frost sweetens leaves
- Onions (sets/transplants): Choose day-length type suited to your latitude
- Potatoes: Soil at least 45°F (UMD); hill as plants grow
- Broccoli: Cool-season; harden off; good fall crop
- Cabbage: Cool-season; harden off; good fall crop
- Tomatoes: Wait for nights reliably above about 52°F (Colorado State)
- Peppers: Need warm soil: about 65°F is optimal for transplanting (UC ANR)
- Eggplant: Transplant after nights stay above 50°F (UMN)
- Beans (bush & pole): Seeds rot in cold, wet soil
- Sweet corn: Soil 60°F+ (UNH, UMN); plant in blocks for pollination
- Cucumbers: Frost-tender; watch for cucumber beetles
- Squash: Frost-tender; watch for squash vine borer
- Pumpkins: For October pumpkins, many sow in late May–June
- Basil: Very cold-sensitive
- Marigolds: Easy warm-season annual
- Zinnias: Easy warm-season annual
- Tulips: Our frost-date window is an approximation of that soil rule. In zone 9, chill bulbs 12–16 weeks first (Clemson)
- Daffodils: Our frost-date window is an approximation of that soil rule; slightly earlier than tulips is fine
- Garlic: Harvest the following early summer
Iowa USDA zone guides: Zone 4 planting guide Zone 5 planting guide Zone 6 planting guide
How we count planting dates: the weeks before or after frost for each crop come from university extension planting guides: UNH Extension, When to Plant Your Vegetable Garden; Rutgers FS787, Starting Vegetable Seeds Indoors; Virginia Tech 426-331, Home Garden Vegetable Planting Guide; University of Maryland Extension, Vegetable Planting Calendar; and University of Idaho CIS 1209 (marigolds and zinnias). Bulb windows approximate Rutgers’ rule to plant when soil falls below 60°F (FS1220), and garlic follows SDSU, Illinois and Virginia Tech. Temperature notes: UMD (potatoes), UMN (sweet corn), UC ANR (peppers, hardening off), UMN (eggplant), Colorado State (tomatoes) and SDSU (hardening off).
Tips for Iowa gardeners
- Watch soil temperature, not just the calendar — warm-season crops stall in cold soil. An inexpensive soil thermometer helps.
- Harden off transplants over 7–10 days before planting out (UC ANR, SDSU).
- Ask your local Cooperative Extension office about varieties and timing for your county; find it in the USDA NIFA land-grant university directory.
- Keep weeds down early — see our weed identification guide.
Frequently asked questions
When is the last frost in Iowa?
Across the 970 Iowa ZIP codes where frost comes in most years, the median last spring frost (32°F, NOAA 1991–2020) at the nearest station is Apr 28, and the middle 80% of ZIP codes range from Apr 20 to May 3. Check the average for your ZIP code, and remember frost can occur after the average date.
When can I plant tomatoes in Iowa?
Transplant tomatoes outdoors 1–2 weeks after your average last frost, once nights stay above about 52°F (Colorado State). Typical dates: Zone 5 areas: May 5 – May 12.
What USDA zone is Iowa?
Iowa spans roughly USDA hardiness zones 4b–6a on the 2023 USDA map (by ZIP code, via PRISM). Hardiness zones describe winter low temperatures, not frost dates.
Other state planting calendars
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