Delaware Plant Hardiness Zones Map And Gardening Guide

Summary

Delaware plant hardiness zones are 7a and 7b. Northern Delaware is zone 7a, and the state’s coastal area is zone 7b. The state’s overall average winter temperatures range from 0°F (-17.8°C) to 10°F (-12.2°C).

Delaware has a humid, subtropical climate. This means the state has warm/hot summers and mild/cold winters. The annual precipitation averages 45.9 inches.¹⁰

Delaware’s growing season is moderate, but it does experience severe weather events, such as coastal storms, flooding, and tornadoes.¹ Preparing for such events and choosing the correct plants for your growing space creates a stronger, more resilient garden. 

Plant suggestions include but are not limited to:^13-27

• Bur Oak 
• Witch Hazel 
• Wild Bergamot 
• Daikon Radish
• Lavender 
• Turmeric 
• Paw Paw
• Wild Stonecrop 

---

Delaware Plant Hardiness Zones

Zone Name	Average Minimum Extreme Winter Temperature Range Fahrenheit (°F) Celsius (°C)	Average Last Frost Date Range In Spring (Beginning Of The Growing Season)	Average First Frost Date Range In Autumn (End Of The Growing Season)
7a	0°F to 5°F -17.8°C to -15°C	Mid-April	Late October
7b	5°F to 10 °F -15°C to -12.2 °C	Early to mid-April	Late October to early November

Frost Date Sources: 3-9

Delaware’s Growing Conditions

General Climate^1-10

Delaware has a humid subtropical climate. This means the state experiences mild-temperate weather overall, with no distinct dry season and a hot summer.  

The northern part of Delaware is in plant hardiness zone 7a, which means it experiences a slightly shorter growing season, with temperatures remaining cooler in the winter months. 

The southern and coastal parts of the state are in zone 7b, which experiences warmer summers and a slightly longer growing season.

Delaware experiences precipitation throughout the year, and droughts rarely occur. Severe thunderstorms can lead to flash flooding and tornadoes in this state. 

Microclimates

USDA plant hardiness zones are an important starting point for your garden, but you’ll also need to consider microclimates. 

Microclimates are areas where specific conditions create a climate different from the climate they’re situated in. 

Buildings, fences, paved areas, or short hills and valleys can create these microclimates. 

They can be as small as a space in your backyard or as large as a city.

In other words, learn about your local conditions from local experts to see if your garden falls into a microclimate.

Extreme Weather^1,10-11

Coastal Storms 

Delaware can experience severe thunderstorms during the spring and summer seasons, which can bring lightning, strong winds, heavy rain, major flooding, and tornadoes to the state. 

This can look like Nor’ Easters in the winter, with strong winds, heavy snowfall, and ice accumulation. Winter garden prep, including mulching, will help keep your plants alive through the winter. 

Planning for these types of weather events is crucial to the protection and survival of your garden. Native plants acclimated to the area will do better than non-native plants, which will be more susceptible to extreme weather. 

Flash Flooding

In Delaware, flooding is the most common extreme weather event. Flooding can be detrimental to a garden and damage plants, property, and tools. Prior planning can help mitigate the damages of flooding. 

Drain and rain garden installations can greatly reduce flooding by directing water away from your property and garden space. 

Water-tolerant plants are also advantageous when working with Delaware’s weather systems. Native plants are more adaptable to the climate and can be resilient in the face of extreme weather. 

Tornadoes

Tornadoes bring high winds, flash floods, hail, and other extreme weather patterns to Delaware. They can be detrimental to your garden, but with a little planning and a whole lot of luck, you can prepare your gardens for tornado season. 

Tornado season typically occurs in mid-spring to early summer. Although tornadoes are not typically common in Delaware, the state can experience one tornado on average a year. 

Choosing plants with strong root systems is a great way to mitigate tornado season. Potting favorite plants and bringing them inside can also increase their survival rate during extreme storms. 

Growing Season¹⁶

Delaware has a moderate growing season. It typically lasts 170-200 days, extending from early April to early November (depending on whether you live in zone 7a or 7b). 

The coast of Delaware can be, on average, 10 degrees warmer in the summer and 10 degrees cooler in the winter. Knowing your zone within the state is helpful, as is knowing what types of plants will do well there. Some plants that thrive on the coast may not grow well in the northern inland area of the state. 

Delaware Gardening Tips

Choose The Right Plants

Choosing the right plants is one of the most critical factors in growing a successful garden. Knowing the species of plant best suited to your particular environment will help create impactful, long-lasting gardens. 

Adding native plants to your garden can increase biodiversity, support pollinators, and withstand region-specific environmental elements. These plants are more resilient, use less water, and help create sustainable landscapes. 

Knowing Your Location¹⁶

There are two distinctly different growing environments in Delaware. One is the Piedmont growing environment, a small portion of the state in the far north corner. Hilly terrain with steep valleys dominates this landscape with lots of rocky, eroded soil. 

Choosing plants that focus on deep root development can help stabilize the soil and build strong foundations in your garden. 

The second growing zone within Delaware is the coastal plains, which cover the majority of the state. A coastal plain environment consists of low-lying tidal estuaries close to the sea. 

This area consists mostly of sandy soil with varying drainage, as some marshes have clay-based soils. Adding organic matter to heavy and sandy soils can break up clay, improve drainage, and build healthy soil. Organic matter can consist of compost or even leaf mulch added to your garden each fall. 

Consult With Local Professionals

Consulting with local gardening professionals allows you to benefit from their experience with your area’s conditions, the plants that do well there, and overall best practices. 

Delaware Plant Suggestions^13-28

Trees

• Bur Oak (Quercus macrocarpa)
• Sweet Birch (Betula lenta)
• Sugar Maple (Acer saccharum)

Shrubs

• Witchhazel (Hamamelis virginiana)
• Silky Dogwood (Cornus amomum)
• Strawberry bush (Euonymus americanus)

Flowers

• Common Yarrow (Achillea millefolium)
• Wild Lupine (Lupinus perennis)
• Wild Bergamot (Monarda fistulosa)

Vegetables

• Daikon Radish (Raphanus sativus longipinnatus)
• Shallot (Allium ascalonicum)
• Potato Red Norland (Solanum tuberosum) 

Herbs

• Lavender (Lavandula ‘Goodwin Creek Grey’)
• Greek Oregano (Origanum vulgare) 
• Lemon Thyme  (Thymus citriodorus)

Spices

• Ginger (Zingiber officinale)
• Turmeric (Curcuma longa)
• Garlic (Allium sativum)

Fruits

• American Plum (Prunus americana)
• Paw Paw (Asimina triloba)
• Red Mulberry Tree (Morus rubra)

Succulents

• Wild Stonecrop (Sedum ternatum)
• Golden Stonecrop (Sedum makinoi) 
• Six-Sided Stonecrop (Sedum sexangulare) 

Disclaimer

Any of the above can change and is not exhaustive. 

Treat anything above like a good starter guide. Then use that as a foundation as you consult with local gardeners, professionals, forecasts, guides, and organizations. 

Sources

1. “Delaware Severe Weather Awareness Week”. National Weather Service. March 11, 2024. Accessed March 22, 2024. 
2. “DELAWARE”. Global Educational Concepts. Accessed March 22, 2024. 
3. “Climate change in Delaware”. Wikipedia. January 10, 2024. Accessed March 22, 2024. 
4. Runkle, Jennifer & Kunkel, Kenneth E. “Delaware – State Climate Summaries 2022”. NOAA. Accessed March 22, 2024.
5. Barton, Susan. “Delaware Gardening: Challenge to Newcomers”. University of Delaware. January 2005. Accessed March 22, 2024.
6. “Frost dates for Middletown, DE”. Almanac. Accessed March 22, 2024.
7. “Frost Dates for Rehoboth Beach, DE”.Almanac. Accessed March 22, 2024.
8. “Frost Dates for Wilmington, DE”. Almanac. Accessed March 22, 2024.
9. “Frost Dates for Bethany Beach, DE”. Almanac. Accessed March 22, 2024.
10. “Delaware’s Climate”. Delaware Climate Office. Accessed March 22, 2024. 
11. “Natural Hazards”. PrepareDE. Accessed March 22, 2024.
12. Kellog, Scott. “Plant Hardiness Zone for Delaware”. Garden Tower. December 9, 2019. Accessed March 22, 2024. 
13. “Native Plants for Delaware Landscapes”. University of Delaware. Accessed March 22, 2024.  
14. “Achillea millefolium (White Yarrow)”. Gardenia.net. Accessed March 22, 2024 
15. Sarver, Mathew J. “Delaware Native Plants for Native Bees”. Delaware Department of Agriculture. 2007. Accessed March 22, 2024. 
16. “Growing and Harvesting in Delaware”.Urban Farmer. 2018. Accessed March 22, 2024.  
17. “Paw Paw”. Nature Hills Nursery. Accessed March 22, 2024. 
18. “Red Mulberry Tree Morus rubra”. Nature Hills Nursery. Accessed March 22, 2024. 
19. “Evergreen Sedum: Stonecrop”. Portland Nursery. Accessed March 22, 2204
20. Mahr, Susan. “Garlic, Allium sativum”. Wisconsin Horticulture. Accessed March 10, 2024
21. Mahr, Susan. “Ginger, Zingiber officinale”. Wisconsin Horticulture. Accessed March 10, 2024
22. “Greek Oregano (Origanum vulgare)”. Salt Spring Seeds. Accessed March 10, 2024
23. “Thymus x citriodorus (Lemon Thyme)” Gardenia.net. Accessed March 10, 2024.
24. “Turmeric”. Wikipedia. March 22, 2024. Accessed March 22, 2024.
25. Baessler, Liz. “Growing Lavender ‘Goodwin Creek Grey’”. Gardening know how. July 26, 2021. Accessed March 22, 2024. 
26. “Daikon Radish -Raphanus sativus longipinnatus”. Great Basin Seed Accessed March 22, 2024. 
27. “Shallot”. Wikipedia. February 28, 2024. Accessed March 22, 2024. 
28. “Red Norland”. Wikipedia. June 2, 2021. Accessed March 22, 2022.