When to Plant in Wilmington, DE: Planting Calendar & Frost Dates

For ZIP 19801 in Wilmington, the nearest NOAA weather station with freeze records is Wilmington Porter Rsch, 3.5 miles away. Its median last spring frost (32°F, NOAA 1991–2020) is Apr 7 and its median first fall frost is Nov 4, leaving about 211 frost-free days. ZIP 19801 is in USDA hardiness zone 7b. The last frost here comes 4 days earlier than the zone 7 median (Apr 11), and the season is 11 days longer than the zone’s typical 200 days. Across Delaware’s 68 ZIP codes with frost dates, the median last frost is Apr 7; Wilmington’s comes on the same day.

Station and dates: NOAA NCEI U.S. Climate Normals 1991–2020, 32°F at 50% probability, for the station nearest the center of ZIP 19801. Zone: 2023 USDA Plant Hardiness Zone Map (PRISM data by ZIP code).

Key planting dates for Wilmington

Wilmington vegetable and flower planting calendar

Every date range below is counted from Wilmington’s median frost dates (Apr 7 and Nov 4) with the same rules as our planner, and rows run in calendar order. In about half of years a frost still comes after the spring date.

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).

Harvest estimates add days to harvest from these sources to each planting window, and stop at the first fall frost for frost-tender crops: 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.

Frost dates across Wilmington’s ZIP codes

All 3 of Wilmington’s ZIP codes map to the same NOAA station, so these dates hold across the city.

Which ZIP codes count as Wilmington: the 3 ZIP Code Tabulation Areas (2020 ZCTAs) with at least half of their land area inside Wilmington city limits, from the U.S. Census Bureau, 2020 ZCTA to Place Relationship File. ZCTAs are the Census Bureau’s approximations of USPS ZIP Code areas, so this list may not match every USPS ZIP code. Each ZIP code’s dates are the ones our planner shows for it.

How Wilmington compares

How this table is built: each ZIP code is matched to its nearest NOAA 1991–2020 freeze-data station (within 60 miles); state and zone rows are medians across those ZIP codes. Zones are the 2023 USDA zones by ZIP code (PRISM).

More for Wilmington gardeners

• Your own ZIP: open the planner for ZIP 19801 and change the ZIP to yours for its own station and dates.
• Delaware: When to plant in Delaware, with frost dates across the state.
• USDA zone 7b: our zone 7 planting guide.
• Frost tonight? How to protect plants from frost.

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