Gardening in Vermont

Hardiness zones in Vermont

Vermont spans USDA hardiness zones 4a to 5b. A hardiness zone measures the average coldest winter temperature at a given site. It does not measure summer heat, rainfall, or soil type. Zone 4a winters run colder than zone 5b winters. A plant rated hardy only to zone 5 may die in a zone 4a yard. Vermont's zone range comes from data gathered at 44 weather stations across the state. That is why towns just a few miles apart can sit in different zones, from 4a up to 5b. Check your own town's zone before you buy a shrub, tree, or perennial. A plant that is only hardy to zone 5 may need winter protection if your spot is zone 4a. That could mean a thick mulch layer, or a pot you can move indoors.

• Zone 4a
• Zone 4b
• Zone 5a
• Zone 5b

Frost dates

Spring's last frost in Vermont falls between April 28 and June 1, depending on where you garden. The first fall frost arrives between September 13 and October 20. These dates mark a 50 percent frost risk. On that date, there is roughly an even chance of frost. A warmer spot near Lake Champlain may see its last frost in late April. A colder, higher spot may still see frost into the first week of June. The same split applies in fall, with some towns safe until late October and others at frost risk by mid-September. Wait until after your area's last frost date to move tender seedlings and warm-season crops like tomatoes outdoors. Plan your fall harvest and any frost covers around your area's first frost date. Because the spread between the earliest and latest dates is wide, a seed packet's calendar date means less here than your own local frost date.

Climate

Across Vermont, the growing season ranges from 103 days to 174 days, depending on location. A 103-day season is short, typical of a cold valley or high elevation spot. A 174-day season gives far more time for slower crops to mature, like long-season tomatoes or winter squash. This range comes from climate data recorded at 44 weather stations spread across the state. Vermont's hardiness zones run from 4a to 5b, and the coldest zones tend to pair with the shortest growing seasons. Elevation, distance from large lakes, and local terrain all shift these numbers from one town to the next. A valley floor near a lake often runs warmer and longer than a hilltop a few miles away. Use your own station's data, not a statewide average, to plan sowing and harvest dates. Gardeners in the shorter-season areas often start seeds indoors and choose quicker-maturing varieties to make the most of the time they have. Gardeners in the longer-season spots have more room to try crops that need a full, warm stretch to ripen.

Season length

Plan your Vermont garden around two numbers: your local last frost date and your local first frost date. Together, they set a growing season of somewhere between 103 and 174 days depending on where you live. Start seeds indoors in late winter so transplants are ready once your last frost date passes. That date falls anywhere from late April to early June depending on where you live. Watch for the first fall frost, which lands anywhere from mid-September to late October, and bring in tender crops before it hits. If you garden in a shorter-season spot, favor quick-maturing varieties and use row covers to stretch both ends of the season.