Delaware’s whole growing range sits inside USDA zones 7a to 8a, and that narrow band is good news for gardeners: of the 65 Trees, Shrubs and Perennials this site tracks, 61 are hardy across the entire state. Only four species run into trouble at one end of the zone or the other, and none fail everywhere.
What will not survive a winter in Delaware
The USDA Plant Hardiness Zone Map, built from the average annual extreme minimum temperature recorded between 1991 and 2020, places Delaware entirely within zones 7a and 8a. That’s a mild, narrow spread as states go, and it shows in the numbers: crossing this state’s zone range against the 65 landscape plants documented on this site turns up zero that fail across the whole territory.
That doesn’t mean every plant on a nursery shelf will thrive here. “Hardy” only measures survival through the cold, and the warm end of a plant’s range is frequently a heat ceiling rather than a cold floor. A species rated hardy through 8a can still sulk through a Delaware August even though it will make it through a Delaware January without damage. Winter survival and summer comfort are two different questions, and this state’s mild zone range only answers the first one.
What this means in practice is that a Delaware gardener rarely needs to cross a plant off the list because of hardiness alone. The short list of species that do run into trouble here are only in trouble in part of the state, not all of it, which is the subject of the next section. There is no “will not survive anywhere in Delaware” table to build, because the facts don’t support one. Manufacturing a failure where none exists would do a reader no favors.
That leaves the real work of choosing plants in Delaware less about hardiness and more about site conditions: soil drainage, summer rainfall, and timing. Those are covered further down. For now, the takeaway is straightforward: the state’s mild, compact zone range means the vast majority of commonly planted Trees, Shrubs and Perennials will survive a Delaware winter without issue.
The plants that work in part of the state and not the rest
Four species out of the 65 documented here are hardy in only part of Delaware’s 7a-to-8a range. That’s the reason a state-level page matters at all: a single yes-or-no answer would be correct for some readers and wrong for others, depending on which end of the zone range they garden in.
| Plant | Type | Does not survive in Delaware’s |
|---|---|---|
| Weigela florida | Shrub | 7a, 7b zones |
| Syringa vulgaris | Shrub | 7b, 8a zones |
| Picea abies | Tree | 8a zone |
| Thuja occidentalis | Tree | 8a zone |
Grouped by where they fail, the pattern splits two ways. Weigela florida struggles in the state’s cooler 7a and 7b zones, meaning it wants the warmest sliver of Delaware to reliably make it through winter. Picea abies and Thuja occidentalis sit at the opposite end: both are fine through most of the state but drop out in the 8a zone, the warmest part of Delaware’s range. Syringa vulgaris fails in both 7b and 8a, leaving only the coldest 7a pocket of the state as reliable ground for it.
None of this comes with a stated mechanism in the source data, and it would be a mistake to guess one. The facts say where each plant fails, not why, so the useful move is to find out which zone applies to your own address rather than assume.
Delaware’s zones don’t split cleanly along county lines from north to south the way some states do; the state’s insulation page carries the county-level zone picture for Delaware, and checking it against your own location is the fastest way to know whether Weigela, Syringa, Picea abies or Thuja occidentalis belong on your planting list or off it.
The soil and the summer they will be planted into
Delaware’s designated state soil is the Greenwich series, an Ultisol: an old, heavily weathered soil that’s naturally acid and low in nutrients, with a surface pH near 6.0. Texturally it runs as a loam to silt loam, about 48 percent sand, 9 percent clay and 43 percent silt, with organic matter around 1.7 percent. It’s classified well drained, which for woody plants matters more than almost any other soil trait, since standing winter water rots roots faster than cold ever kills them outright.
What the texture and drainage mean for planting
A soil that’s mostly silt and sand with only 9 percent clay drains fairly freely. That’s an advantage against winter wet, but it also means the ground holds less water reserve through a dry stretch than a heavier clay soil would. Low organic matter, at 1.7 percent, compounds that: organic matter is what helps soil hang on to moisture and nutrients between rains, so a Greenwich-series bed with little of it will dry out and lean out faster than the same rainfall would suggest on richer ground.
The slightly acid pH near 6.0 happens to suit several of the shrubs commonly planted in Delaware, including the state’s native hollies and Kalmia latifolia, which generally prefer acid soil. But the Greenwich series is a representative value for the state, not a reading of any particular yard; a garden on fill dirt, a river bottom, or ground a builder has graded can differ completely, and a soil test remains the only way to know an actual pH and organic-matter number for a given bed.
Reading the summer rainfall against that soil
Delaware averages about 13.1 inches of rain across June, July and August, with August running driest at 3.98 inches against June’s 4.67 and July’s 4.41. Cross that figure with the soil rather than treating it on its own: on the sandy-silt, well-drained Greenwich series, that rain moves through the root zone quickly and doesn’t linger the way it would on a heavier clay soil elsewhere. The same 13.1 inches supports a plant differently depending on what it’s falling onto, which is exactly why summer rainfall numbers and soil texture need to be read together rather than converted into a fixed watering routine.
When to plant, here
At the reference weather station used for Delaware’s climate normals, the last spring frost falls between April 3 and April 14, and the first fall frost arrives between October 26 and November 7. Those two windows frame when a woody plant can go into the ground with a reasonable shot at building roots before it’s asked to either leaf out or face a hard freeze.
| Season | Best suited for | Main risk |
|---|---|---|
| Spring (after April 3-14) | Most Trees, Shrubs and Perennials; a full growing season to establish before winter | A late frost can still nip new growth if planting starts too early |
| Autumn (September through late October) | Many trees and shrubs, since cooling soil and lower heat stress favor root growth over leaf demand | Less time to root before the first fall frost, especially in the coldest part of the state’s zone range |
The logic behind both windows is the same: a newly planted woody species needs time to establish roots before it’s forced to support either summer heat and leaf growth or a hard freeze. Spring planting gives a full season for that root work, but risks a late cold snap right after planting. Fall planting takes advantage of cooler air and often still-warm soil, but in Delaware’s zone range that window narrows as you move toward the colder end of the state, since less time separates a September planting from the first fall frost around late October or early November.
These frost dates come from a single reference station and are averages over 1991-2020, not a guarantee for any particular week. Suburban and rural sites, especially away from the coast or at any elevation, commonly see the last spring frost arrive later and the first fall frost arrive earlier than the station dates suggest. Whichever window is used, a newly planted tree or shrub needs regular water through its first season regardless of what its mature drought tolerance rating says, since those ratings describe plants that are already established, not ones just settling into the ground.
Where to read about each one
Among the trees hardy across the whole of Delaware, the documented list includes Acer rubrum, Acer saccharum, Amelanchier canadensis, Betula nigra, Carpinus caroliniana, Cercis canadensis, Cornus florida, Ginkgo biloba, Juniperus virginiana, Lagerstroemia indica, Liquidambar styraciflua, Magnolia grandiflora, Nyssa sylvatica, Pinus strobus, Platanus occidentalis, Quercus alba, Quercus rubra and Tilia americana.
Shrubs that clear the whole state include Aronia arbutifolia, Buxus sempervirens, Clethra alnifolia, Fothergilla gardenii, Hydrangea macrophylla, Hydrangea paniculata, Ilex glabra, Ilex verticillata, Itea virginica, Kalmia latifolia, Physocarpus opulifolius, Spiraea japonica and Viburnum dentatum. Weigela florida and Syringa vulgaris belong on this list only for readers in the right zone, as covered above.
On the perennial side, species hardy statewide include Achillea millefolium, Amsonia hubrichtii, Asclepias tuberosa, Baptisia australis, Echinacea purpurea, Heuchera americana, Iris sibirica, Lavandula angustifolia, Monarda didyma, Phlox paniculata, Rudbeckia fulgida, Salvia nemorosa and Hylotelephium spectabile.
Every hardiness figure used on this page comes from a university extension plant database, crossed against Delaware’s local USDA zone range as recorded on this site. These are hardiness ranges built for survival through cold, and they’re a separate measure entirely from the adaptation ranges used elsewhere on this site for apple varieties, which track something different and shouldn’t be read against these numbers.