Hardiness Zone Map Change

Those of us with gardens in Connecticut, especially along the sound, have always been on the edge of things warmer. We dreamed of warmer weather plants such as camellias, sweet box, gold dust plant and crape myrtle in our coastal gardens. A few brave gardeners have planted these southern beauties in protected corners and gone to great lengths to protect their prized garden gems from winter's cold fingers. Now with warmer temperatures and winters moderating these garden beauties can be included in our plant palette.

The United States Department of Agriculture (USDA) just issued the latest Plant Hardiness Zone Map for the United States. The revised map now shows some regions of Connecticut which used to be a Zone 6b are now a Zone 7a. This means that some of those Zone 7 plants that you have always desired growing will now survive in certain locations. Weather changes to the coastal areas now indicate that southerly portions of Fairfield and New Haven Counties are in Zone 7a.

Plants that are now able to be grown in parts of southern Connecticut and coveted by most gardeners when they visit their more southerly neighbors include: Some varieties of Crape Myrtle, some varieties of Camellias, Sweet box, Gold Dust Plant, Needle palm trees. Several notable perennials formerly were considered annuals can now be planted and expected to survive including Gunnera, cardoon, verbena some lilies and many others. The most important things this means for designers and gardeners in our area is that our palette of plants to choose from has been greatly expanded.

Camelias which have always been a staple of the southern gardens, but just out reach of the Connecticut gardeners now are a viable choice. A broad selection of camellias are hardy to Zone 7 can be planted and some cold hardy camellia varieties have now been developed that are considered hardy to USDA Zone 6 with protection. These include: Camellia 'April Remembered', C. 'April Kiss', C. 'April Tryst', C. 'Pink Icicle', C. 'Polar Ice', C. 'Winter's Joy', C. 'Winter's Rose', C. 'Winter's Snowman' and C. 'Winter's Waterlily'.

Another staple of southern gardens is Crapemyrtle (Lagerstroemia indica). There are many Crape myrtles hybrid that are mostly hardy to USDA Zone 7, but can be killed to the ground in severe winters. There are a few varieties that are root hardy to Zone 6 and can be treated as perennials. Lagerstroemia fauriei is known to be reliably hardy to USDA Zone 6, but avoid planting them on a south-facing wall where the winter sun might break their dormancy too early. Zone 6 hardy or root hardy Crapemyrtles include: Lagerstroemia indica 'Burgundy Cotton', L. indica 'Red Rocket', L. indica 'Tightwad', L. indica 'Becky's Watermelon Red', L. 'Sarahs Favorite' and L. fauriei cultivars - 'Bashams Party Pink', 'Biloxi', 'Choctaw', 'Hopi'. The Fleming Filigrees cultivars are hardy to USDA Zone 4.

Local microclimates can affect plant health and survivability in your area so be aware if your area tends to be colder or warmer than the norm indicated on the USDA Zone Map. Often properties near to lakes or ponds will have a more moderate air temperature and possibly a zone warmer, whereas if you are in a valley the cold air tends to settle so you may be a bit colder. Urban areas, because of the heat island effect of the mass of asphalt and buildings tend to make them a zone warmer than surrounding non-urban areas. Some areas with more consistent snow cover can consider planting species that are from a zone warmer, since the root zone is insulated during the winter months.

How will this affect your garden or landscape? Plants that are growing in your garden now have adapted to the seasons and the gradual changes in minimum temperatures of the region. You should not worry if they are growing or thriving now. Just make sure to continue to plant any new species that are tested and labeled for your hardiness zone.

When trying out new plants in your garden always try one or two of each species first to ensure that they really like your garden and will survive. These alternatives are sure to bring joy to many gardens.

The USDA Zone Hardiness Map is available as an interactive tool online at http://www.planthardiness.ars.usda.gov. You are also able to find your zone by entering your zip code.

USDA Hardiness Zone Map for Connecticut
Temperatures Included in Each Zone

Zone 5: -29 to -23 C (-20 to -10 F)
Zone 6: -23 to -18 C (-10 to 0 F)
Zone 7: -18 to -12 C (0 to 10 F)

Rock Spring Design Group, LLC
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