Fruit Trees for Janesville, Beloit and the Rock River, Wisconsin

On February 3, 1996, NOAA's station at the Fort Atkinson wastewater plant read −39°F, the coldest reading on record anywhere on this map. The Beloit station, 29 miles away and downriver, at nearly the same elevation (787 and 788 feet), read −25°F. That 14°F split is what growing fruit trees for Janesville, Beloit and the Rock River comes down to. The map covers Rock County and the edges of Dane and Jefferson counties in southern Wisconsin, from Fort Atkinson and Stoughton down through Edgerton, Milton and Janesville to Beloit, with Clinton and Orfordville on the uplands.

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 is the 30-year planning low, the number our cold hardiness calculator uses (built from NOAA station records since the 1995-96 winter), with a small nudge for the ground right around you. It's a safe number to plan around, not the record and not a promise of how often it comes. The MFTC zone is that number in half zones. The typical winter is an average year's coldest night, the kind of average USDA's map uses. The spring layer shows how much warmer or colder a spot runs than Janesville on a still, clear night at bloom.

Janesville plans for −26°F, MFTC zone 4a, with a typical winter of −13°F, and that's the middle of the map: nine tenths of the growing ground falls between −29°F and −24°F. The warm end is high ground with somewhere to drain, like Mount Zion east of Janesville (−23°F) and Allens Grove, Avalon and Fairfield on the eastern upland (−24°F to −25°F), all MFTC 4b. The cold end is the north: the Lake Koshkonong flats plan for −29°F, and Fort Atkinson and Blackhawk Island for −30°F. The spring layer swings wider, from 2°F colder than Janesville at the coldest named spots, low along the rivers, to 13°F warmer on Mount Zion.

Why the map looks the way it does

Everything here drains to the Rock. The river leaves Lake Koshkonong at 774 feet and Wisconsin at 731 feet, falling just 1.4 feet per mile through Rock County, and it has cut 30 to 120 feet into a deep fill of glacial sand and gravel below uplands at 800 to 900 feet. Side valleys feed that long, nearly level trough: the Yahara and Badfish Creek from the northwest, Marsh Creek above Janesville, Bass Creek near Afton and Turtle Creek into Beloit. On a clear, calm night the ground radiates its heat to the sky, the chilled air slides down those creeks to the river, and most of the pool is made right on the floor. A floor this flat doesn't drain. The cold just sits.

That's why the north end is coldest. Fort Atkinson sits on the river bottom by the mouth of the Bark River, north of the last ice sheet's terminal moraine, where marshes fill kettle basins away from streams. Below town the river spreads into Lake Koshkonong, 10,460 acres but only 6 feet deep on average, once a marsh of reeds and wild rice. A wide, shallow basin can pool harder than a deep valley that drains, peaty ground gives back little heat on a clear night, and a lake that shallow freezes early and quits helping by midwinter. The Fort Atkinson station was the coldest in the group, or tied for it, in six big outbreaks from 1959 to 1996.

Position beats elevation. Beloit's station, in town at 788 feet, sits about 37 feet above the river-bottom point the map uses for Beloit, near the height of the Beloit College terrace, and it was the mildest station, or tied for it, in 10 of the 12 big outbreaks on file: −21°F on January 30, 1951, when Stoughton read −35°F. The wastewater plant stations sit low (Afton's on the river, Stoughton's about 40 feet below the town point, Clinton's 25 to 35 feet below the village), and each plans 1°F to 2°F colder on its own records than the map gives its spot. So down by the water, plan a degree or two colder than your number. Towns hold some heat, and the map gives built-up ground up to 2.5°F.

Height alone doesn't buy warmth. Clinton's station, at 924 feet on the old Jefferson Prairie, is 136 feet higher than Beloit's yet runs a median 5°F colder for the year's coldest night. Flat, open prairie radiates freely on a still night and has nowhere to send its cold; Rock Prairie east of Janesville, its old braided channels only about 2 feet deep, is like that. What counts is height above the nearest low ground. Mount Zion sits 160 feet above its floor, and around Janesville the benches and bluff tops plan for a median −24°F against −27°F on the river floor. A 1930s Michigan study found orchard ridges only 25 to 30 feet above the plain could be nearly as frost-free as high hills.

There's no big water to soften it; orchards near Lake Michigan bloom late behind the cold lake, but Rock County is well inland. Snow is the wild card: air over snow runs colder, but 4 to 10 inches of it insulates the soil, and after the snowless 2024-25 winter UW-Madison's fruit program found apple damage just below the graft union. And deep arctic air fills everything: on January 31, 2019, every station reporting in and around the map landed between −26°F and −33°F, and Beloit set its record low of −29°F.

Janesville: downtown, the bluffs and the river floor

The Rock splits Janesville. The river-side stations sit near 760 feet and the city's listed elevation is 850 feet, about 90 feet higher. The map puts downtown, on the flat east bank, on a toe slope at the edge of the pool: −26°F, MFTC 4a, typical winter −13°F, with town heat helping. Within 3 miles the river floor plans for −27°F and the benches and bluff tops −24°F. Courthouse Hill, the 1800s residential hill near downtown, and Look West, on the bluff along the west bank by the Lincoln-Tallman House, are hill and bluff ground, likely closer to that bench number than to the floor. The Old Fourth Ward grew up around the river mills, and its streets near the water are floor ground. Rotary Botanical Gardens, on the East Side, sits in an old sand pit, and a hollow like that can fill with cold air on a still night.

Anderson, 2.4 miles north and 60 feet above its floor, plans for −26°F and reads 5°F warmer than Janesville at bloom; Lochwood, up the river, −27°F. Downtown's −26°F leaves room for Liberty and Northern Spy apples, Stanley plum and Montmorency tart cherry (all −30°F), and plenty for Honeycrisp and Haralson (−45°F). Lapins and Gold sweet cherries (−35°F) and Contender peach (−30°F) clear it too, but they bloom early, so give them the bluff tops.

Beloit, South Beloit and Turtle Creek

Beloit sits where Turtle Creek meets the Rock at the Illinois line. The map's Beloit point, on the river bottom at 751 feet, plans for −27°F, MFTC 4a, typical winter −14°F, 1°F colder than Janesville at bloom; within 3 miles the floor plans for −27°F and the benches −25°F. The Near East Side and Beloit College sit on an outwash terrace 40 feet above the east shore with the river bluff along their west edge, so cold air there has somewhere to fall, and the Beloit station, at about that height, has a median 175 frost-free days, the longest on the map. Big Hill Park's west-bank bluffs are the same kind of ground.

North of town, Garden Village and Crestview plan for −27°F, and Holiday Hills, low by the river, reads 2°F colder than Janesville at bloom, as cold as any named spot on the map. Christilla Heights, 2.5 miles northwest and 80 feet above the floor, plans for −25°F (4b) and reads 4°F warmer. Turtle Creek falls about 5 feet a mile off the southeast upland and carries cold air down into Beloit on still nights; Shopiere and Tiffany, up the creek, plan for −27°F and −28°F. South Beloit plans for −28°F and Rockton −27°F, and the Rockford map carries on down the Rock.

On Beloit's floor, Bartlett pear, Superior and Italian plums and Paula Red apple (all −35°F) have 7°F or more to spare, and Zestar!® (−40°F) more; the Apple Hut in Beloit opens with both. Veteran peach and Rainier cherry (−30°F) clear the floor by only 2°F to 3°F, and the station hit −29°F in 2019, so put them on the terrace or at Christilla Heights.

Milton, Rock Prairie and Mount Zion

East of the river the land rises onto Rock Prairie, a high outwash plain, tallgrass at settlement, running east from Janesville into Walworth County. It drains water freely and cold air hardly at all. Johnstown Center (932 feet) and Emerald Grove (899 feet) plan for −26°F and read 1°F colder than Janesville at bloom, though they sit 120 to 160 feet higher than downtown. Mount Zion, between Janesville and Johnstown Center at about 1,035 feet, is the warmest named spot on the map: −23°F, MFTC 4b, a typical winter of −10°F, and 13°F warmer than Janesville at bloom. Avalon and Fairfield, 50 to 70 feet above their floors, plan for −25°F (4b) and read 4°F to 5°F warmer.

Milton, at 875 feet by a narrow outwash valley, plans for −27°F, MFTC 4a, typical winter −14°F, even with Janesville at bloom, with almost no bench ground within 3 miles. Milton Junction, about a mile west and 30 feet above its floor, plans for −26°F and reads 3°F warmer. Here Snowsweet® (−45°F), Cortland and Ure pear (−40°F), and Toka (−45°F) and Superior plums have room. Toka is a good pollenizer for Superior; our pollination maps show what pairs with what. Save Harlayne apricot (−30°F) and Blushingstar peach (−25°F) for Mount Zion and the upland slopes that plan for −25°F or warmer.

Clinton, Allens Grove and Jefferson Prairie

Clinton sits on the high, open country of southeastern Rock County at about 950 feet, on the old Jefferson Prairie, where Norwegian settlers started the Jefferson Prairie Settlement in 1838. The map plans for −26°F in the village, MFTC 4a, typical winter −14°F, 2°F warmer than Janesville at bloom; Bergen, 4 miles south, plans for −25°F.

Here I'd trust the station over the map. The Clinton plant carries a 30-year number of −28°F on its own records, 2°F colder than the map gives its spot, and runs a median 5°F colder than Beloit, 9 miles away. It has the latest median last spring frost of any station on the map (May 9) and the shortest season (150 days). Nobody has studied why, but the physics fits: flat, open prairie radiates hard on a still night, and a spot a little below its surroundings collects the cold. In Clinton, plan for −28°F and lean on trees rated −35°F or colder: Honeycrisp and Wolf River (−45°F), Luscious pear, Alderman plum and Meteor tart cherry (−40°F). Allens Grove, 5.4 miles east and 70 feet above its floor, is the other face of this country: −24°F, MFTC 4b, and 7°F warmer than Janesville at bloom, the kind of slope for Westcot apricot (−45°F).

Edgerton, Lake Koshkonong and Fort Atkinson

Edgerton, once "Tobacco City U.S.A." with as many as 52 tobacco warehouses, sits a five-minute drive from Lake Koshkonong. It plans for −27°F, MFTC 4a, typical winter −13°F, 3°F warmer than Janesville at bloom, with the benches around it at −25°F. Hans Addition, just east of town and 90 feet above the floor, plans for −26°F and reads 8°F warmer at bloom.

On the lake shore the two layers part ways. The winter numbers barely move (−26°F to −29°F), because the deep winter nights fill the whole basin and the 30-year number takes the fine terrain at only a quarter strength. Indian Heights, Highwood, Mallwood and Maple Beach plan for −27°F to −28°F but read 6°F to 9°F warmer than Janesville at bloom, because cold air slides off them to the water; Coopers Shores, down at the water nearby, reads even with Janesville. Koshkonong Mounds, on a 17 percent slope, reads 9°F warmer, while the lake-level points (Lake Koshkonong, North Shore, Stony Point) plan for −29°F and read within 1°F of Janesville. On the slopes, Sungold apricot (−40°F) and Siberian C peach (−35°F) have a real shot at a crop.

Fort Atkinson, on the river bottom at 788 feet, 5.5 miles above the lake, is the cold end of the map: −30°F, MFTC 4a, typical winter −15°F, with the floor around it at −29°F. Blackhawk Island, 3.5 miles down toward the lake, plans for −30°F, MFTC 3b. The town floods now and then, and the station holds the area's −39°F record, so plant for the record: Wealthy (−50°F), Frostbite (−45°F), Centennial applecrab (−50°F), Summercrisp pear (−40°F) and Evan's Bali tart cherry (−45°F), on ground that doesn't flood.

Stoughton, Dunkirk and the Yahara

The Yahara comes down from Madison's lakes through Stoughton, past Dunkirk, Stebbinsville and Fulton, to the Rock about 9 miles northwest of Janesville, and its bottom is a cold-air drain. Dunkirk and Stebbinsville plan for −28°F and read 1°F to 2°F colder than Janesville at bloom; Cooksville plans for −28°F too, and Fulton and Indianford (at the dam on the Rock below the lake) −29°F.

Stoughton straddles the Yahara about 20 miles southeast of Madison. The town point plans for −27°F, MFTC 4a, typical winter −13°F, and reads 5°F warmer than Janesville at bloom. The wastewater plant station, about 40 feet lower, shows what the bottom does: −35°F in 1951 and −33°F on January 31, 2019, the coldest station on the map that morning. In town, Riverwood Estates, on the river bottom south of downtown, plans for −28°F and reads 1°F colder than Janesville at bloom; Rolling Acres, 0.2 miles away and 30 feet higher, −27°F and 3°F warmer. Pleasant Hill, Country Club Estates, Greenbriar Estates, Oak Knoll and Petty Acres, 30 to 70 feet above the floor west and north of town, plan for −26°F. Farther up the Yahara, the Madison map takes over. On the bottoms I'd want −35°F or colder, like Empire apple and Danube tart cherry; up in the subdivisions, Contender peach and Rainier cherry (−30°F) have 4°F of room.

Orfordville, Footville, Evansville and the southwest hills

In the southwest, west of the river, the glacial drift thins to a few feet or nothing, bedrock ridges top 1,000 feet, and Bass Creek, Coon Creek and the Sugar River have cut valleys 170 to 190 feet deep. Orfordville, 60 feet above its floor and with more bench ground within 3 miles than any other town on the map, plans for −27°F, MFTC 4a, typical winter −13°F, 1°F warmer than Janesville at bloom, with the floor around it at −28°F and the benches −26°F. Footville and Magnolia plan for −27°F (Magnolia reads 3°F warmer at bloom), and Evansville, on the west edge, −28°F. The hillsides southwest of Orfordville carry clay loam only 1 to 2 feet over limestone, thin soil that dries out fast. The Sugar River and Coon Creek bottoms once held about 45 percent of the county's poorly drained land, and low, wet ground runs cold on frost nights, so plant the slopes above. Golden Russet (−40°F) and Clapp's Favorite pear (−30°F) suit the benches.

Spring frost and bloom along the Rock

The spring layer follows the same drainage as winter, at full strength. It reads warmest on slopes with low ground below to take the cold (Mount Zion 13°F warmer than Janesville, Mallwood and Koshkonong Mounds 9°F, Hans Addition 8°F, Allens Grove and Indian Heights 7°F) and coldest in flat bottoms with nowhere to send it (Holiday Hills, Indianford and Stebbinsville 2°F colder). Open blossoms of nearly every tree fruit start dying near 28°F, and UW-Madison fruit specialist Amaya Atucha says that at bloom a 1°F difference can decide the crop.

NOAA's 1991 to 2020 station records show the same order. The median last 32°F comes April 22 at Beloit, April 28 at Fort Atkinson and the Afton plant, April 29 at Stoughton and May 9 at Clinton, with the last 28°F about two weeks earlier; one spring in ten it comes May 6 or later at Beloit and May 18 to 21 at Stoughton, Clinton and Fort Atkinson. Seasons of 150 to 175 frost-free days are longer than the 135 days the University of Vermont uses to mark short-season fruit country.

Bloom frost is the one to watch here. In 2012 a warm March pushed early bloom into several freezing nights, and just south of the map in northern Illinois some growers reported near-total apple losses. On May 14 and 15, 2016 a late frost hit apples and grapes across southern Wisconsin, with losses from none to 95 percent, and in 2026 early bloom and frost cut apple yields in parts of the state.

The fix is mostly site. Put apricots, peaches and sweet cherries on the slopes that read warmest, and keep apples, pears, honeyberries and bush fruit for flatter ground: only about 15 percent of apple blossoms need to set for a crop, and fully open haskap (honeyberry) flowers take 19°F. A hedge, fence or tree line across the bottom of a slope backs cold air up into the trees above it, so gap it. Through bloom, mow short, don't till, and water a day or two before a frost; frost cloth of 0.5, 0.9 and 1.5 ounces per square yard gains about 4°F, 6°F and 8°F.

What the weather records say

NOAA station records here go back to 1893 at Beloit. The coldest readings on file: −39°F at Fort Atkinson (February 3, 1996); −37°F at Whitewater and −36°F at Brodhead, just off the map, and −35°F at Stoughton (all January 30, 1951); −31°F at the Afton plant (February 3, 1996); −29°F at Beloit (January 31, 2019, in 109 years on file); −28°F at the old Janesville station (1951) and at Clinton (2009). Since 1995, five of the six stations reporting have gone below their own 30-year number at least once, Fort Atkinson's −39°F against −31°F among them. So I like a few degrees of room. Timing matters too: the median first 32°F comes October 6 at Clinton and October 14 at Beloit, and a freeze before trees harden off kills at temperatures a January tree shrugs off, so we taper water from mid-August.

The Afton plant and Beloit average −15°F and −14°F for the year's coldest night, on the line between USDA zones 5a and 5b, which is where USDA-style listings put Janesville. Our MFTC zone for Janesville is 4a, more than a full zone colder, because NOAA station records show the worst night in about 30 winters runs a median 14°F below a station's average winter low.

What you can grow here

Bluff tops, benches and the high eastern upland: −25°F or warmer

Mount Zion, Allens Grove, Avalon, Fairfield, Christilla Heights and the bluffs around Janesville and Beloit.

• Apples: Liberty, Northern Spy and Cox Orange Pippin (−30°F).
• Pears, plums, cherries and grapes: Harrow Sweet pear, Stanley and Shiro plums, Rainier, Stella and Montmorency cherries, Concord grape (all −30°F).
• Apricots and peaches: Harlayne and Tomcot (−30°F); Contender (−30°F), Blushingstar and Redstar peaches and Hardired nectarine (−25°F).

The river floor, the towns and the open prairie: −26°F to −28°F

Janesville, Beloit, Milton, Edgerton, Stoughton, Orfordville, Evansville, the Yahara bottoms and Clinton.

• Apples: Freedom, Empire and Paula Red (−35°F); Zestar!®, Cortland and Golden Russet (−40°F); Honeycrisp (−45°F).
• Pears and plums: Bartlett and Seckel (−35°F), Ure (−40°F); Italian and Superior (−35°F) with Toka.
• Cherries: Lapins and Gold (−35°F), Meteor (−40°F).
• Peaches and apricots: Contender and Veteran (−30°F), Siberian C (−35°F); Hardy Iowa apricot (−35°F) on a slope. Worth a try: Blushingstar (−25°F), 1°F to 3°F short, against a south wall in town.
• Berries and vines: honeyberries and Montana Black Currant (−50°F), Pixwell gooseberry and Boyne raspberry (−40°F), Frontenac grape (−35°F).

Fort Atkinson, the Koshkonong flats and the coldest bottoms: −29°F to −30°F

Fulton and Indianford plan for −29°F too. With −39°F on record at Fort Atkinson, favor −40°F and colder.

• Apples: Wealthy (−50°F), Haralson, Frostbite and Wolf River (−45°F); Kerr (−50°F) and Trailman (−60°F) applecrabs, the ones to plant if you only plant one tree.
• Pears and plums: Ure, Summercrisp and Luscious (−40°F); Toka (−45°F), Alderman and Black Ice (−40°F).
• Cherries and apricots: Evan's Bali (−45°F), Meteor (−40°F); Westcot and Morden 604 apricots (−45°F) on the slopes above the flats.
• Berries: honeyberries, Montana Black Currant and Aronia (−50°F), Red Lake currant (−40°F).

Roots are the weak link: dormant apple roots are seriously hurt near 10°F while the wood above takes about −40°F, so the snowless winter is the dangerous one. On the gravel outwash and the thin soils southwest of Orfordville, ground dries out fast; pick the hardiest rootstock you can, mulch, and keep the soil moist into winter. The peat and old marsh ground around Koshkonong runs cold and drains slowly, so test drainage first (dig 2 feet, fill, let it drain, refill; under 10 hours is well drained). Drip is the only irrigation we advise.

Fruit history here

George J. Kellogg started a nursery in Janesville in 1854 and is remembered as the "Father of Orcharding in Wisconsin"; the State Horticultural Society was organized at the 1865 State Fair in Janesville. The winter of 1898-99 killed nearly all the apple trees in his nursery, and budded plums were badly killed while plums on their own roots did fairly well. By 1909 Kellogg's Nursery was starring varieties for the far north, and at least six are still in our catalog: Wealthy, Malinda, Northwest Greening (his Northwestern Greening), the Whitney and Transcendent crabs, and Montmorency. No commercial fruit industry had followed by 1922, when the soil survey found home orchards, largely neglected, in tobacco country. Today the Stateline area's fruit is u-pick: Hawks Orchard in Milton (about 2,000 dwarf and semi-dwarf trees), the Apple Hut in Beloit, Ten Eyck in Brodhead.

Questions people ask

What growing zone is Janesville, WI?

Janesville plans for −26°F, MFTC zone 4a, with a typical winter of −13°F. The Afton plant and Beloit average −15°F and −14°F for the year's coldest night, right on USDA's 5a/5b line. USDA's zone is based on an average winter, ours on the bad night we plan for.

When is the last frost in Janesville and Beloit?

NOAA station records for 1991 to 2020 put the median last 32°F at April 22 in Beloit and April 28 at the Afton plant south of Janesville. One spring in ten it comes May 6 or later at Beloit and May 14 or later at Afton.

Can you grow peaches in southern Wisconsin?

Yes, with the right variety and spot. Contender and Veteran (−30°F) clear the planning low on nearly all the ground here, Siberian C (−35°F) clears all of it, and Blushingstar (−25°F) fits the bluff tops and eastern upland. They bloom early, so plant them on slopes that read warm at bloom.

Why is Clinton, WI colder than Beloit?

The Clinton station runs a median 5°F colder than Beloit's for the year's coldest night and gets 150 frost-free days to Beloit's 175. The likely reason is that Clinton sits on flat, open prairie that radiates hard on still nights, while Beloit's station is in town at terrace height. In Clinton, plan for −28°F.

Does Lake Koshkonong keep the shore warmer?

Not in winter. It's only 6 feet deep on average, so it freezes early, and the lake-level points plan for −29°F. What helps is slope: Indian Heights, Mallwood, Maple Beach and Koshkonong Mounds read 7°F to 9°F warmer than Janesville on a still bloom night, because cold air drains off them to the water.

What fruit trees grow best in Rock County, Wisconsin?

Most ground here plans for −26°F to −28°F, which suits Honeycrisp, Zestar!® and Cortland apples, Bartlett and Ure pears, Superior and Italian plums with Toka as a pollenizer, Lapins cherry, Contender peach, honeyberries and currants. Fort Atkinson and the Koshkonong flats call for −40°F trees like Haralson and Evan's Bali.

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.