Fruit Trees for Worcester, Lowell, Nashua and the Merrimack Valley, Massachusetts and New Hampshire

On the calm, clear night of November 21, 2013, the Worcester airport, up on its hill at about 1,000 feet, bottomed out at 29°F, and so did Boston. Hanscom Field in Bedford, on low ground, fell to 16°F and the Fitchburg airport to 17°F (Blue Hill Observatory logged it). That's the first thing to know about fruit trees for Worcester, Lowell, Nashua and the Merrimack Valley: height above the nearest low ground counts for more than height above the sea.

The map covers Central Massachusetts and the Nashua and Merrimack valleys: Worcester and its hill towns, Fitchburg and Leominster, the Nashoba Valley orchard towns, Lowell and its suburbs, MetroWest out to Concord, the inner Boston suburbs on its east edge, and southern New Hampshire from Nashua and Hudson up the Souhegan to Milford and Greenville. Type your address in the box on the map to get the number for your own place, and the list of what we sell that has come through it.

How to read this map

The big number at any spot is its 30-year planning low, the bad winter night we'd plan a tree around, the same number our cold hardiness calculator uses, with a small nudge for the lay of the land. It runs conservative, so treat it as a safe number to plan for, not a forecast of how often it comes. The MFTC zone is that number in half zones, and the typical winter is an average year's coldest night, the kind of number USDA's map is built on. The spring layer shows how many degrees warmer or colder a spot runs than downtown Worcester on a still, clear night at bloom, and every spring reading on this page is against downtown Worcester.

Downtown Worcester, the reference town, plans for −19°F (MFTC 5a, typical winter −5°F). The middle of the growing ground plans for −17°F, and half of it falls between −19°F and −16°F, which is mild country by our standards. The coldest 5 percent plans for −23°F or colder: the bottoms of the Nashua and Souhegan and the hill towns along the New Hampshire line, where North Ashburnham, the coldest named place on the map, plans for −28°F (4a). The warmest 5 percent, −13°F or warmer, is mostly the inner Boston suburbs; downtown Boston plans for −10°F (6a). Most of what we sell has come through colder than anything on this map, so here the spring layer does more of the sorting than the winter number.

Why the map looks the way it does

North of the Worcester hills nearly everything drains to the Merrimack: the Nashua down from Fitchburg and Wachusett Reservoir through Lancaster, Groton and Pepperell; the Souhegan out of New Ipswich through Greenville and a narrow valley to Wilton, then a broadening one through Milford; and the Sudbury and Assabet, which meet at Egg Rock in Concord and run to Lowell as the Concord River. Worcester itself drains south down the Blackstone. On a calm, clear night most of the cold is made right on those floors as the ground loses heat to the sky, and more slides in off the hills after sunset. The worst floors are flat and slow: the Sudbury falls only about 227 feet in 32.7 miles, and meadows like Great Meadows on the Concord and Bolton Flats on the Nashua are low, wet, grassy ground, the kind that runs coldest on a still night.

The NOAA station records show how hard those floors pool. Over 22 shared winters the old Nashua station ran a median 11°F colder in its yearly low than Lowell, 10 miles down the Merrimack. The Lake Cochituate station, at 151 feet, ran a median 16°F colder than Boston's old city station, and 9°F colder than Blue Hill, 474 feet higher, over 59 winters. In the cold snap of February 16, 1943, the station a couple of miles north of downtown Nashua read −35°F, the coldest reading in this map's station records, while Lowell read −29°F, Lake Cochituate −28°F, the old station in Worcester −24°F, Blue Hill −18°F and Chestnut Hill only −10°F.

Above the floors sits the thermal belt, where the cold drains past and a layer of warmer air rides over the pool. Here that's mostly hills, drumlins like Lowell's Fort Hill and knobs like Westford's Prospect Hill, Birch Hill in Hollis and Federal Hill in Milford, 170 to 490 feet above the nearest floor. On the winter number they're only a few degrees milder, but on the spring layer they're a different world: Birch Hill, 490 feet above the floor, runs 14°F warmer at bloom, while East Groton, on low ground with no height above its floor, runs 8°F colder. A Hungarian study of 69 clear, calm nights found a valley floor averaging 6.7°F colder than a slope 230 feet higher.

Elevation by itself doesn't decide it. The Worcester airport station sits at 1,002 feet and its own 30-year number is −16°F, milder than the Nashua airport and Hudson stations' −21°F about 800 feet lower. Its median last spring frost, April 22, comes 18 days before Milford's, and its frost-free season runs 178 days to Milford's 143, the shortest of any station here with frost dates.

Town heat shows up where the city is big and dense: Boston's TV forecasters describe pavement keeping the city warm on still nights while the suburban valleys fill with cold. The mill cities sit on their river floors, though, and the floor wins. Downtown Lowell plans for −18°F, Worcester −19°F and Nashua −21°F, about the same as the floor around each. There's no big lake to help either; we haven't found any record of Wachusett Reservoir, Lake Quinsigamond or kettle ponds like Walden warming anything past their shores. Snow matters more. Worcester's hills average about 64 inches a season and Fitchburg about 71, against about 56 at Lowell and 52 at Nashua, and a good snowpack keeps roots far warmer than the air above it.

Worcester and its seven hills: Tatnuck, Union Hill, Pakachoag and the Blackstone floor

Worcester is called the city of seven hills, and the Blackstone River forms in the middle of the city, where the Middle River and Mill Brook meet, then runs underground through downtown. That low ground is the reference for the whole map. Downtown sits 20 feet above the floor and plans for −19°F. Lincoln Square, on the same low ground, plans for −18°F and runs 3°F colder at bloom, and Westwood Hills on the west side, valley ground despite the name, plans for −17°F and runs 5°F colder.

Climb out and the spring picture changes fast while the winter number hardly moves. Tatnuck, 230 feet above the floor, plans for −16°F and runs 11°F warmer at bloom. Union Hill plans for −16°F and runs 11°F warmer, and Pakachoag −16°F and 10°F warmer. Burncoat, on a bench in the north end, is the mildest Worcester neighborhood I checked at −14°F, MFTC 5b. Shrewsbury sits on a bench 270 feet above the floor east of Lake Quinsigamond and plans for −14°F (5b), 9°F warmer at bloom, and Malden Hill near West Boylston plans for −13°F and runs 13°F warmer. Holden, Paxton and Leicester all plan for −16°F.

In the city the winter isn't what limits you. Every apricot, peach and sweet cherry we sell has come through −20°F or colder, so the question is bloom. Put an apricot like Tomcot or Harlayne, a Contender peach or a Lapins cherry up on Tatnuck, Union Hill or Pakachoag, and keep the low lots around Lincoln Square for apples, haskap and currants.

Lowell, Chelmsford, Dracut and Westford on the Merrimack

Lowell grew up at the bend where the Merrimack drops over Pawtucket Falls and the Concord comes in, on low ground about 100 feet up, and the glaciers left drumlins on both sides of the river. Downtown and the Acre plan for −18°F (5a). Centralville, on low ground north of the river, plans for −18°F and runs 2°F colder at bloom, and Middlesex Village, on the floor west of downtown, runs 7°F colder. Belvidere, on Fort Hill and Lynde Hill, plans for −15°F (5b) and runs 9°F warmer, and the top of Fort Hill 11°F warmer. Christian Hill, the drumlin in eastern Centralville on the Dracut line, plans for −16°F and runs 11°F warmer too. The Lowell station, at 110 feet, has a 30-year number of −17°F.

Westford is the best lesson on the map. The Center sits on its hill 210 feet above the floor and plans for −15°F, 7°F warmer at bloom, and Prospect Hill plans for −15°F and runs 13°F warmer. Down in the villages, Graniteville plans for −19°F and runs 2°F colder, Nabnasset runs 4°F colder, and Forge Village plans for −19°F and runs 7°F colder. That's about a 19°F spread on a spring frost night inside one town. Chelmsford plans for −17°F and Dracut −18°F, while Billerica, on a bench 140 feet above the floor, plans for −14°F (5b). Tyngsborough, on the Merrimack toward Nashua, plans for −21°F (4b), and from there north the valley gets colder.

Nashua, Hudson, Hollis and the Souhegan valley in southern New Hampshire

Cross into Hillsborough County and the floors run colder. Downtown Nashua, on a drainage channel where the Nashua River runs through to the Merrimack, plans for −21°F, MFTC 4b, with a typical winter of −7°F. That's colder than anything a Nashua station has recorded since 1995; the coldest was −19°F at the automated station at Nashua's airport in the 1995 to 1996 winter. Across the river, Hudson plans for −21°F on river-bottom ground, and Lincoln Park, west of downtown, −22°F. Gilboa Hill in the south of the city, 270 feet above the floor, plans for −17°F and runs 10°F warmer at bloom, against about even for downtown.

West of the city the land climbs. Hollis village, 180 feet above the floor, plans for −18°F and runs 5°F warmer at bloom, and Birch Hill near the west line plans for −18°F and runs 14°F warmer. Hollis has long been orchard country; Brookdale Fruit Farm, Lavoie's and Lull Farm are all there. Brookline, west of Hollis, plans for −22°F. Down in the Souhegan it's colder: Milford −23°F on the river bottom, Wilton −23°F, and Greenville, above the narrow stretch of valley that runs down to Wilton, plans for −25°F (4a); cold air backs up above a narrows. Federal Hill south of downtown Milford, 460 feet above the floor, plans for −18°F and runs 14°F warmer at bloom. Toward Salem, Windham plans for −22°F and Salem −19°F, and the old Windham station ran a median 11°F colder than Lowell over 20 winters. North of Litchfield toward Merrimack and Manchester, the Concord and Manchester map covers you.

Harvard, Bolton, Lancaster and the Nashoba Valley orchard towns

This is the old orchard belt, and the map shows why the orchards sit where they do. The Nashua forms at Lancaster at 233 feet, where the North Nashua from Fitchburg meets the South Nashua from Wachusett Reservoir, then runs north past Bolton Flats and the Oxbow, and that floor is cold. Lancaster, Clinton, East Bolton and Ayer all plan for about −20°F, right on the line between 4b and 5a, and Pepperell plans for −22°F (4b). The Pepperell and Clinton stations both hit −26°F in January 1984.

Up on the ridges the spring is different. Harvard's town center, 170 feet above the floor, plans for −17°F and runs 8°F warmer at bloom, and Still River village on the west side plans for −16°F and runs 6°F warmer. In Stow, Marble Hill plans for −16°F and runs 13°F warmer, while Gleasondale, down on the Assabet, plans for −19°F and runs 3°F colder. Groton's center is on a bench at −18°F, and hills like Brown Loaf east of it plan for −16°F and run 12°F warmer. Mount Lebanon, southwest of Pepperell center, plans for −17°F and runs 13°F warmer.

The orchards have the proof. In the May 18, 2023 freeze, George Hill Orchards in Lancaster lost 80 to 90 percent of its apples on its low, flat blocks, about 60 percent on the slopes and very little on its high ground (the Boston Globe). At Carlson Orchards in Harvard the damage ran heaviest on the bottom limbs, where the coldest air hugs the ground. When frost came again on April 20 and 21, 2026, as low as 29°F in Worcester County, Westward Orchards in Harvard told the Harvard Press the higher parts of its orchards fared better.

Concord, Sudbury, Framingham and the MetroWest meadow rivers

The Sudbury, Assabet and Concord are meadow rivers, slow and grassy for miles. Saxonville, where the Sudbury runs through north Framingham, plans for −21°F (4b), and Cochituate −20°F; the old Lake Cochituate station hit −28°F in January 1935 and again in February 1943. Wayland plans for −19°F and runs 4°F colder at bloom. On the Assabet, Hudson plans for −20°F (4b) and Maynard −19°F on the river bottom, 4°F colder at bloom. Concord, where the rivers meet, plans for −17°F, and the old Concord station ran a median 12°F colder than Boston's city station over 32 winters.

The ground between the rivers is better. Natick center plans for −14°F (5b). Hopkinton, on a bench 200 feet above the floor, plans for −14°F (5b) and runs 9°F warmer at bloom, the best spring reading of the MetroWest town centers I checked. Acton plans for −15°F and runs 5°F warmer, Marlborough −16°F and Sudbury −17°F, while Southborough and Westborough sit lower at −18°F and −19°F.

Fitchburg, Leominster and the hill towns on the New Hampshire line

Fitchburg sits on the North Nashua at 467 feet and plans for −18°F (5a); its airport station has a 30-year number of −17°F and a median last frost of April 29. Leominster, mostly on a plateau above the river, plans for −16°F, and Lunenburg, on a bench 210 feet above the floor, plans for −15°F (5b) and runs 9°F warmer at bloom. Princeton village, at 1,126 feet south of Wachusett and 410 feet above its floor, plans for −18°F but runs well over 10°F warmer at bloom.

West and north of there the land climbs toward Wachusett, Watatic and the Monadnock foothills, the cold corner of the map. Westminster plans for −21°F, Ashby −23°F and Ashburnham −24°F, and over the line Mason plans for −22°F and New Ipswich and Temple −23°F. North Ashburnham, at 1,081 feet with no height above its floor, plans for −28°F (4a), and the Ashburnham North station has the coldest 30-year number of any station on the map, −27°F, against −19°F at the other Ashburnham station. Around Jaffrey and West Peterborough, the Keene and Monadnock map covers you.

Cambridge, Somerville, Newton and the Boston edge

The east edge of the map is its warm end. Beacon Hill plans for −9°F, downtown Boston and Somerville −10°F (6a), and Cambridge and Newton −12°F (5b). The Logan airport station, on the harbor, has a 219-day frost-free season. Low ground still pools: Watertown, on the Charles at the floor, plans for −15°F and runs 5°F colder at bloom. Great Blue Hill in Milton, 560 feet above the floor, plans for −13°F and runs 14°F warmer. Chicago Hardy Fig (−10°F) clears the number downtown and on Beacon Hill, and in Cambridge or Newton it's worth a try against a south wall.

Spring frost and bloom from Worcester County to the Souhegan

The FAO's frost protection manual calls site choice "the single most important method of frost protection," and the 1991 to 2020 frost dates in NOAA station records follow the map. The median last 32°F in spring comes April 4 at Logan, April 18 on Blue Hill, April 22 at the Worcester airport, April 28 at Lowell, May 6 at Hanscom and May 10 at Milford. The last 28°F, where open blossoms start dying, comes April 10 at the Worcester airport and April 26 at Milford, and one year in ten the last 32°F comes after May 7 at the airport but after May 21 at Milford.

Harvard growers treat the second week of May, after Mother's Day, as the end of frost risk. The May 18, 2023 freeze came after that, with lows in the mid to upper 20s°F when apple fruitlets were already set, and the state's apple crop came in about 25 percent short (UMass); Harvard lost its whole peach, nectarine and cherry crop. February had already hurt. On February 4, 2023, right after the warmest January on record in Massachusetts, it went to −13°F, most stone fruit flower buds were dead within a week, and the state had no peach crop. A tree dehardened by a warm spell gets hurt by cold it would shrug off in a normal January.

Bloom is coming earlier too. In Concord, Thoreau recorded the first highbush blueberry flowers on May 11, 1853; in 2012 they opened April 1 (Richard Primack's Walden Warming), which puts bloom into more frost nights. Open blossoms start dying near 28°F, but only about 15 percent of apple blossoms need to set for a crop, and open haskap flowers take 19°F. Carlson Orchards treated its April 2026 losses as natural thinning, which fits what we've seen: most fruit can lose half its blossoms with little effect.

So put apricots, peaches, sweet cherries and plums on hills with good spring readings (Tatnuck, Pakachoag, Fort Hill, Gilboa Hill, Westford Center, Hopkinton, Harvard center), apples, haskap and bush fruit lower down, and pears off the frosty bottoms. An east slope warms early on a frosty morning, a north slope holds early bloomers back, and a hedge across the foot of a slope dams cold air uphill of it. Doe Orchards in Harvard runs wind machines on its coldest nights; a wind machine gains a third to a half of the inversion's strength on a still night and nothing in a windy freeze.

What the weather records say

The coldest reading in this map's NOAA station records is −35°F north of Nashua on February 16, 1943. The same cold snap gave Lowell its record, −29°F, and the old Worcester station −24°F, the same −24°F Worcester's published climate table lists as the city's record. The Worcester airport station's own record is −19°F on January 15, 1957, and the Windham station hit −31°F in January 1971. In the cold snap around February 9, 1934, the winter that killed many Baldwin orchards, Lake Cochituate read −27°F, Lowell −21°F and Boston's city station −18°F.

The cold since 1995 hasn't matched those winters. In the February 4, 2023 cold snap, one of the sharpest lately, Ashburnham North read −23°F, Greenville −22°F, Lowell −14°F, the Worcester airport −13°F and Jamaica Plain −11°F, its record. USDA's map puts Worcester in 5b and 6a, built on an average winter; on the bad night we plan for, downtown is 5a.

What you can grow here

Most of our list clears winter on this map, so choose by site and bloom. Every pick below has come through cold at or below its band's planning low.

Hills, benches and the inner suburbs, −16°F or warmer (Tatnuck, Union Hill, Burncoat, Shrewsbury, Lunenburg, Westford Center, Billerica, Belvidere, Acton, Natick, Hopkinton, Cambridge, Newton). Nearly everything we sell: Baldwin, Northern Spy and Macoun apples; Seckel and Harrow Sweet pears; Stella and Skeena sweet cherries; Goldrich and Wenatchee Moorpark apricots; Glohaven and Redstar peaches; Hardired nectarine; Shiro plum; and even Persimmon (Montana Trial) and Javid's Iranian Seedling almond (−20°F).

The valley floors and mill-city bottoms, −17°F to −21°F (downtown Worcester, Lowell, Fitchburg, Framingham, Concord, Lancaster, Clinton, Ayer, Hudson, downtown Nashua). Everything we sell rated −25°F or colder clears winter here, but spring is the problem, so lean on apples like Honeycrisp, Liberty and Zestar!®, plus Honeyberry, Red Lake currant, Invicta gooseberry and Aronia. Save the nearest rise for Toka and Superior plums (Toka is a good pollenizer for Superior; see our pollination maps), Blushingstar peach and Bartlett pear.

The New Hampshire hill towns and the coldest bottoms, −22°F to −28°F (Pepperell, East Groton, Brookline, Milford, Wilton, Windham, Ashby, Ashburnham, Mason, New Ipswich, Temple, Greenville). Pick from what's rated −30°F or colder: Haralson, Wolf River and Cortland apples, Luscious pear, Mount Royal plum, Evan's Bali tart cherry, Westcot apricot and Siberian C peach. Blushingstar has come through −30°F, so it fits here too in a good spot, and Baldwin (−20°F) is worth a try where the number is −25°F or warmer.

Plant on a slope, not a windswept top and not the bottom, and clear brush that dams cold air at the foot of the slope. Roots are the weak link in a cold winter and snow protects them, so a snowless cold snap is the one to worry about. UNH and UMass both steer fruit to deep, well-drained sandy loam, away from heavy, wet soil. Paint the south and west sides of trunks with diluted white latex against winter sun. UNH says a 6 to 8 foot deer fence is the only fully effective deer control, and 1/4 inch hardware cloth guards 18 inches tall, buried an inch, keep voles off. The May 2023 freeze seems to have set off a fire blight outbreak (UMass), brown rot is the worst peach disease in Massachusetts, and spotted lanternfly has turned up in Fitchburg, Shrewsbury, Worcester and Southborough.

Fruit history here

The Roxbury Russet came up in Roxbury, now part of Boston, in the mid 1600s and is believed to be the oldest apple bred in the country. The Baldwin started as a chance seedling after 1740 on a farm in Wilmington, was spread by Col. Loammi Baldwin of Woburn, and became the most popular apple in 19th century New England. Many Baldwin orchards were lost in the hard winter of 1933 to 1934, and a lot of growers replanted with McIntosh. Ephraim Wales Bull raised the Concord grape at his home in Concord in 1849, after about 22,000 seedlings. Johnny Appleseed was born in Leominster, Harvard had its Shaker village and Fruitlands, and at Tower Hill in Boylston an orchard holds 119 apple varieties from before the 20th century.

Questions people ask

What growing zone is Worcester, Massachusetts?

USDA's map puts Worcester in 5b and 6a, based on an average winter. On the bad night we plan for, downtown Worcester is −19°F, MFTC zone 5a, with a typical winter of −5°F. The hills run milder: Burncoat plans for −14°F (5b) and Tatnuck for −16°F.

Is Worcester colder than Lowell or Nashua?

It's snowier, but on still nights it's often warmer. On November 21, 2013 the Worcester airport bottomed at 29°F while Hanscom Field in Bedford hit 16°F. The airport station's 30-year number is −16°F; downtown Lowell plans for −18°F and downtown Nashua for −21°F.

When is the last frost in Worcester County?

At the Worcester airport the median last 32°F is April 22 and the last 28°F April 10 (1991 to 2020), and one year in ten the last 32°F comes after May 7. Low valley stations run later: May 8 at Hudson and May 10 at Milford. The May 18, 2023 freeze shows frost can still come after Mother's Day.

Can you grow peaches around Worcester and Nashua?

Yes. Contender and Blushingstar (both −30°F) and Siberian C (−35°F) clear the planning low everywhere on this map. The crop is the risk: after a warm January and then −13°F on February 4, 2023, Massachusetts had no peach crop. Plant peaches on a hill with a good spring reading, never in a low spot.

Where are the frost pockets around Lowell and Nashua?

The low ground along the rivers and brooks: Forge Village and Graniteville in Westford, East Groton, Middlesex Village and Centralville in Lowell, and Windham, 2°F to 8°F colder than downtown Worcester at bloom. The warm spots are the drumlins and knobs, like Fort Hill and Christian Hill in Lowell, Gilboa Hill in Nashua and Birch Hill in Hollis, 10°F to 14°F warmer at bloom.

Warmer spots, colder spots

Here's the number to plan for at named places on the map, warmest first. Each one is the 1-in-30-year low for that spot: the cold hardiness calculator's number from the same weather stations, sharpened by our microclimate model for the ground right there. Zone is our MFTC zone, set by that one bad night, not by an average.

The weather stations behind it

These are the long-record stations in and around this map, with each one's own numbers since the winter of 1995-96. The last column is this map's 30-year number right at the station, which won't match the station exactly: it's a blend of the stations around it, the way the calculator works everywhere.

Source: NOAA records through ACIS, winters 1995-96 through 2025-26. What the "carried forward," "gaps filled" and AWOS rows mean is explained in how our microclimate maps work.