Zone 6b: What Grows and How to Garden There

What a zone 6b winter means

In a typical zone 6b winter, the coldest night stays above the point where peach and sweet cherry flower buds start to die (about -10°F, according to Virginia Tech). That makes tree fruit far more dependable than in zone 5. Virginia Tech also warns that buds are less hardy than that rule suggests when cold follows a warm spell, when the cold lasts for days, or when trees were stressed the summer before; then damage can begin at 0°F or warmer. The same pattern applies to shrubs at the edge of their range: a sudden plunge after a mild spell does more harm than steady cold.

Where zone 6b is

Zone 6b covers much of Ohio, including Columbus, Cleveland, Cincinnati and Toledo; western Pennsylvania around Pittsburgh; Detroit and southeastern Michigan; Buffalo and Rochester near the Great Lakes; and eastern Massachusetts including Boston, plus Connecticut and Rhode Island. In the middle of the country it includes Kansas City and the Missouri and Kansas plains, and parts of Kentucky, West Virginia and Virginia. In the West it covers Boise and the Snake River valley, Spokane, and valleys in Utah, Colorado, New Mexico, Nevada, Arizona and Oregon.

Fruit trees and small fruit

Apples, pears, peaches, tart and sweet cherries and plums all grow here. Virginia Tech found that cultivars differ: after a severe winter, ‘Red Haven’ blocks kept 83-98% of buds alive while ‘Redskin’ kept none. Spring frost is the bigger risk to the crop. Penn State lists peach blossoms at full bloom losing about 10% at 27°F and 90% at 24°F, and Wisconsin Extension notes that small trees can be covered with a tarp on a frosty night.

Northern highbush blueberries suit 6b (Ohio State). Hardy kiwi, rated to -25°F, needs about 150 frost-free days, which most of the zone has.

Figs are worth trying against a south-facing wall. The University of Tennessee rates ‘Hardy Chicago’ top growth to about 10°F and roots to -20°F; plants that freeze back regrow and fruit on new wood. NC State also names ‘Brown Turkey’, ‘Brunswick’ and ‘Celeste’.

Perennials, bulbs and shrubs

Peonies grow best in zones 5-7 (NC State), and tulips, daffodils, lilies, hostas and daylilies are all reliable.

Southern shrubs that become possible in 6b:

• Crape myrtle: Virginia Cooperative Extension rates it hardy to 6b, with dieback in colder winters.
• Camellias: Ackerman hybrids are rated to zones 6a-6b (Virginia Tech). Tea-oil camellia has withstood brief -10°F. Plant on the north or northwest side of a barrier, away from winter sun and wind (NC State, Washington State).
• Bigleaf hydrangea: flower buds are the weak point; see the FAQ below.
• Azaleas and rhododendrons: Rutgers attributes most winter injury to temperature swings, drying winds and late fertilization. An east or north exposure prevents winter sunburn.

Special concerns

Boise, Spokane and other western 6b cities have dry winters with little snow cover. Utah State and Colorado State both recommend watering evergreens whenever the ground is not frozen, to prevent winter burn on south and southwest sides.