Zone 7 Conditions
Zone 7 typically has a growing season of about 180 days. This works well for potatoes, which have maturity dates ranging from 75 to 120 days depending on the variety. The last frost date is between late March and mid-April, while the first frost usually occurs in mid-November. Winter lows usually range from 0 to 10°F (-18 to -12°C). Some Zone 7 areas see snow.
No matter what your USDA Zone, local conditions can mitigate temperatures. A large body of water such as a lake, for example, may make a difference of several degrees. High altitudes can also affect winter lows. On the other hand, cold air settles, so a Zone 7 garden in a valley may be colder than a Zone 7 garden a few hundred feet up the slope. Elevation can also affect summer temperatures by 10 degrees or more.
Choosing Potato Varieties
Gardeners in Zone 7 can grow early, mid-season or late varieties. There are some possibilities:
- Banana – mid-season
- Centennial Russet – late
- French Fingerling – mid-season
- Green Mountain – late
- Sangre – mid-season
- Snow White – late
- Snowden – late
- Viking Red – early
- Yellow Finn – early
- Yukon Gold – early.
Planting Potatoes in Spring
The key element in spring planting is the date of the expected last frost. Potato sprouts and leaves are frost-sensitive. If you are concerned about a late frost, then sprout, or chit your seed potatoes about four to six weeks prior to the expected last frost date. They should develop sprouts and few leaves. Plant the sprouted potatoes two weeks prior to your expected last frost date.
Planting Potatoes in Summer
You can usually plant potatoes in early summer in Zone 7. Make sure there is adequate soil moisture and choose an early or mid-season variety to allow them to mature. In hot summer areas, this crop may not do as well as spring-planted potatoes. If your area has potato beetles, a summer planting may cause problems; use row covers and organic controls to deal with the insects.
Planting Potatoes in Fall
Some Zone 7 gardeners plant their potatoes in late fall. This can be a good strategy in areas with the potato beetle, as the insects will go into hibernation before the potatoes sprout. Do not chit the seed potatoes. Plant in a 12-inch trench half-filled with rotten leaves. The warmth will prevent potatoes from freezing and they will sprout and grow in spring.