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Flowers Growing Season

The following is a chart of the USDA zones and their frost dates.

This map supersedes U.S. Department of Agriculture Miscellaneous Publication 814, "Plant Hardiness Zone Map," which was revised in 1965. This 1990 version shows in detail the lowest temperatures that can be expected each year in the United States, Canada, and Mexico. These temperatures are referred to as "average annual minimum temperatures" and are based on the lowest temperatures recorded for each of the years 1974 to 1986 in the United States and Canada and 1971 to 1984 in Mexico. The map shows 10 different zones, each of which represents an area of winter hardiness for the plants of agriculture and our natural landscape. It also introduces zone 11 to represent areas that have average annual minimum temperatures above 40 °F (4.4 °C) and that are therefore essentially frost free.

Cold Hardiness Ratings for Selected Woody Plants. Representative plants are listed under the coldest zones in which they normally succeed. Zone Ratings -- Average Annual Minimum Temperature Range.

Zone 1 Below -50°F (-45.6°C)

Last Frost Date:
June 15
First Frost Date:
July 15
Number of Frost Free Days:
30

Betula glandulosa (Dwarf birch), Empetrum nigrum (Crowberry), Populus fremuloides (Quaking aspen), Potentilla pensylvanica (Pennsylvania cinquefoil), Rhododendron lapponicum (Lapland rhododendron), Salix reticulate (Netleaf willow)

Zone 2 -50 to -40°F (-45.6 to -40°C)

Last Frost Date:
May 15
First Frost Date:
August 15
Number of Frost Free Days:
90

Betula papyrifera (Paper birch), Cornus canadensis (Bunchberry dogwood), Elaeagnus commutata (Silverberry), Larix laricina (Eastern larch), Potentilla fruticosa (Bush cinquefoil), Viburnum trilobum (American cranberry bush)

Zone 3 -40 to -30°F (-40 to -34.5°C)

Last Frost Date:
May 15
First Frost Date:
September 15
Number of Frost Free Days:
120

Berberis thunbetgii (Japanese bayberry), Elaeagnus angustifolia (Russian olive), Junipercus communes (Common juniper), Lonicera tatarica (Tatarian honeysuckle), Malus baocata (Siberian crabapple), Thuia occidentalis (American arborvitae)

Zone 4 -30 to -20°F (-34.5 to -28.9°C)

Last Frost Date:
May 10
First Frost Date:
September 15
Number of Frost Free Days:
125

Acer saccharum (Sugar maple), Hydrangea paniculata (Panicle hydrangea), Juniperus chinensis (Chinese juniper), Ligustrum amurense (Amur River privet), Parthenocissus quinquefolia (Virginia creeper), Spiraea x vanhouttei (Vanhouffe spirea)

Zone 5 -20 to -10°F (-28.9 to -23.3°C)

Last Frost Date:
April 30
First Frost Date:
October 15
Number of Frost Free Days:
165

Cornus florida (Flowering dogwood), Deutzia gracilis (Slender deutzia), Ligustrum vulgare (Common privet), Paithenocissus tricuspidata (Boston ivy), Rosa multiflora (Japanese rose), Taxus cuspidata (Japanese yew)

Zone 6 -10 to 0°F (-23.3 to -17.8°C)

Last Frost Date:
April 15
First Frost Date:
October 15
Number of Frost Free Days:
180

Acer palmatum (Japanese maple), Buxus sempervirens (Common boxwood), Euonymus follunei (Winter creeper), Hedera helix (English ivy), Ilex opaca (American holly), Ligustrum ovalifolium (California privet)

Zone 7 0 to 10°F (-17.8 to -12.3°C)

Last Frost Date:
April 15
First Frost Date:
October 15
Number of Frost Free Days:
180

Acer macrophylium (Bigleaf maple), Rhododendron Kurume hybrids (Kurume azalea), Cedrus atlantica (Atlas cedar), Cotoneaster microphylla (Small-leaf cotoneaster), Ilex aquifolium (English holly), Taxus baccata (English yew)

Zone 8 10 to 20°F (-12.3 to -6.6°C)

Last Frost Date:
March 10
First Frost Date:
November 15
Number of Frost Free Days:
245

Arbutus unedo (Strawberry tree), Choisya temata (Mexican orange), Olearia haastii (New Zealand daisy-bush), Pittosporum tobira (Japanese pittosporum), Prunus laurocerasus (Cherry-laurel), Viburnum tinus (Laurestinus)

Zone 9 20 to 30°F (-6.6 to -1.1°C)

Last Frost Date:
February 15
First Frost Date:
December 15
Number of Frost Free Days:
265

Asparagus setacous (Asparagus fern), Eucalyptus globulus (Tasmanian blue gum), Syzygium paniculatum (Australian bush cherry), Fuchsia hybrids (Fuchsia), Grevillea robusta (Silk-oak), Schinus molle (California pepper tree)

Zone 10 30 to 40°F (-1.1 to 4.4°C)

Last Frost Date:
January 20
First Frost Date:
December 20
Number of Frost Free Days:
335

Bougainvillea spectabilis (Bougainvillea), Cassia fistula (Golden shower), Eucalyptus citriodora (Lemon eucalyptus), Ficus elastica (Rubber plant), Ensete ventricosum (Ensete), Roystonea regia (Royal palm)

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