Delaware Frost Dates & Growing Season Guide
Delaware (DE) spans USDA hardiness zones 7a, with growing seasons ranging from 190 days in Newark to 201 days in Dover. The average growing season across the state is approximately 195 days.
Delaware City Frost Dates
The table below shows the average last spring frost date, first fall frost date, growing season length, and USDA hardiness zone for each city. Click a city name for detailed planting calendars and zone information.
Planting Windows for Delaware
Based on average frost dates, here are the recommended planting windows for each city. The indoor seed start date is approximately seven weeks before the last spring frost. Transplanting should occur about two weeks after the last frost. The last direct sow date for fall crops is ten weeks before the first fall frost.
| City | Start Seeds Indoors | Transplant After | Last Direct Sow |
|---|---|---|---|
| Dover | February 21 | April 24 | August 19 |
| Wilmington | February 24 | April 27 | August 16 |
| Newark | February 26 | April 29 | August 13 |
Gardening in Delaware
Delaware's small size belies its garden-friendly climate. Most of the state falls in zone 7a, with a growing season around 195 days that supports a wide variety of vegetables, herbs, and flowers. The coastal plain soils are sandy and well-drained, making them excellent for root crops and herbs but requiring more frequent watering and organic matter additions. Summer humidity encourages fungal diseases, so proper plant spacing and morning watering help prevent problems. Sweet corn, lima beans, tomatoes, and peppers are popular crops. The moderate climate also allows for productive fall gardens with crops like kale, spinach, and Brussels sprouts planted in August.
Understanding Delaware's Hardiness Zones
Delaware includes USDA hardiness zones 7a. These zones indicate the average annual extreme minimum winter temperature for each area, which determines which perennial plants, trees, and shrubs can survive winter without protection. When purchasing trees, shrubs, or perennial flowers, always check that the plant is rated for your hardiness zone or a lower (colder) zone number.
Tips for Using Delaware Frost Dates
These frost dates represent long-term averages and should be treated as guidelines rather than guarantees. In any given year, the actual last spring frost or first fall frost may arrive one to three weeks earlier or later than the average. Factors that affect your specific location include elevation above the city center, proximity to water, slope direction, and whether you are in an urban or rural area. South-facing slopes and areas near large pavement or building masses tend to be warmer than surrounding open land. Low-lying valleys and exposed hilltops are often colder than mid-slope positions.
To protect against late spring frosts, keep row cover fabric, old bed sheets, or frost blankets on hand. Monitor your local weather forecast daily as the average frost date approaches. When frost is predicted after you have transplanted, covering plants in the late afternoon traps ground heat and can protect against temperatures down to about 28 degrees Fahrenheit. For fall season extension, the same covers protect mature plants from early frosts, often buying several additional weeks of harvest.