Gardening in Rhode Island

Hardiness zones in Rhode Island

Rhode Island spans three USDA cold hardiness zones, from 6b to 7b. A hardiness zone marks the average lowest winter temperature a location sees in a typical year. A plant rated for zone 6b or higher should survive the coldest nights across most of the state. The zone number says nothing about summer heat, rainfall, or soil type, only about winter cold. Zone 6b marks the coldest parts of Rhode Island, and zone 7b marks the mildest. Zone 7a falls in between the two, and it is the third zone found in the state. Check your specific zone before you plant something rated near the edge of this range. A plant tagged hardy only to zone 7b may not survive the coldest nights in zone 6b areas.

• Zone 6b
• Zone 7a
• Zone 7b

Frost dates

Your last spring frost date marks the start of the outdoor growing season. Across Rhode Island, that date ranges from April 7 in the mildest spots to May 3 in the coldest. Gardeners in the mildest pockets can often start outdoor planting weeks before those in the coldest ones. The first fall frost works the same way in reverse. It arrives as early as October 8 in the coldest spots and as late as November 13 in the mildest. These dates mark a 50% chance of frost, not a guarantee. Frost can still strike a week or two on either side of these dates in a given year. Use the date for your own area, not a statewide average, when you decide when to set out seedlings or bring tender plants indoors.

Climate

The climate figures on this page come from 11 weather stations spread across Rhode Island. Winter cold varies across the state, from zone 6b in the coldest spots to zone 7b in the mildest. Spring also arrives at different times depending on where you garden. The average last spring frost falls between April 7 and May 3, and the average first fall frost falls between October 8 and November 13. That spread between stations means the frost-free growing season runs from as short as 159 days to as long as 216 days. A state this size can still hold real differences in frost timing and season length from one town to the next. These figures cover cold hardiness zones, frost dates, and season length only. They do not cover summer heat, rainfall, humidity, or soil, since that data was not part of this count. Check conditions local to your own site for anything beyond these two measures before you plant.

Season length

The length of the frost-free growing season changes a lot depending on where you garden in Rhode Island. At its shortest, the season runs about 159 days from last frost to first frost. At its longest, in the mildest parts of the state, it stretches to about 216 days. The shortest and longest season lengths differ by a sizable stretch of the calendar. A shorter season favors fast-maturing crops and starting seeds indoors ahead of your last frost date. A longer season gives you more room for a second planting or for crops that need more time to mature. Match what you plant, and when, to the season length where you live rather than to the state average.