Which Root you are on
The Root is a system, not a stream, and the trout live in one corner of it. The DNR's water-trail page describes the main river forming from the North and Middle branches in the west, picking up the South Branch above Whalan, and running past bluffs to Rushford, where the valley opens into pasture and cottonwood on the way to the Mississippi; from Chatfield to the mouth it drops 310 feet, about 3.4 feet per mile. The main stem is somewhat cloudy from the erodible soils, and the fish list the DNR gives for it is smallmouth bass, channel catfish, rock bass, sunfish, crappies and rough fish, with brown trout only on the western end of the South Branch. The spring-fed South Branch, born at Mystery Cave in Forestville State Park, is the trout river.
This page's gauge, USGS 05385000 near Houston, is below Rushford with 1,250 square miles above it, so it reads everything: the three branches, Rush Creek, and every storm on the plateau. The hub's other gauge, near Pilot Mound, is on the North Branch above Chatfield. Neither sits on the South Branch, so use Houston as a trend and a warning rather than a wading number for Preston.
Forestville down to Preston and Lanesboro
The DNR's Lanesboro fisheries office manages the South Branch in three pieces. From the top through Forestville State Park down to Carimona it is maintained as a wild brown trout stream, with 22,000 brook trout fingerlings a year stocked at Seven Springs at the upstream end of the designated water. From Carimona past Preston the state adds 58,000 brown fingerlings every other year plus rainbow yearlings and fingerlings, and below the Highway 52 bridge downstream of Preston it stocks 130,000 brown fingerlings a year with more rainbows. The office calls the South Branch an underutilized trout resource with excellent hatches of March Browns, Light Hendricksons and several caddis, and notes that below Preston the water is big enough for a canoe or drift boat while the Root River State Trail lets a walking angler cover long distances to wadeable water.
Camp Creek, which joins the South Branch at Preston, is worth the detour: the same office reports around 50 browns over 12 inches per mile near its mouth, rising to about 200 per mile in the upstream easement, with much of the lower creek under easement and the state trail alongside it.
What the Lanesboro shop is fishing
Root River Rod Co. sits in Lanesboro and writes the reports. Its June account has caddis thick in late morning and early evening, Sulphurs from afternoon into dusk, March Browns lingering on shaded water and cloudy days, and ants, beetles and early hoppers fooling fish at midday; the box it recommends is an Elk Hair Caddis in 14 to 16, a Sulphur Sparkle Dun in 16, a Parachute Adams in 14 to 18, Blowtorch nymphs in 16 to 18, foam ants and beetles, and small streamers like Thin Mints, fished dry-dropper early and late, single dries during the hatch, 5x or 6x in the clear water, and streamers when a storm colors things up. For the January opener the shop's list is Pink Squirrels, Zebra Midges, jig nymphs and eggs in the deep pools, slow seams and tailouts, fished late morning to mid afternoon on sunny days after cold nights.
Bob Blumreich's Driftless chart, written for the Wisconsin side of the same region, fills in April olives and late-July-to-October Tricos.
Smallmouth on the big river, and two paddling alerts
Below Whalan the Root becomes a smallmouth river that the DNR maps as two paddling sections, Chatfield to Rushford and Rushford to the Mississippi, with a gentle to moderate flow, a few riffles and levels that swing hard with rain. Minnesota's southern-zone bass rule applies: catch and release from March 1 through May 22, 2026, a harvest season from May 23 through September 13 of six largemouth and smallmouth combined, and catch and release again from September 14 through February 28, 2027. Two things were posted on the water trail in 2026: reconstruction of the Mill Street bridge at Peterson closed the Peterson carry-in access and requires a portage once overhead work begins, and the former Brightsdale Dam site near mile 60 on the North Branch near Lanesboro has unexpected rapids inside a channel-restoration area that the DNR asks paddlers to portage.
Three seasons, and the park-and-city exception
Southeast Minnesota streams, which the 2026 regulations define as those in Houston, Fillmore, Mower, Dodge, Olmsted, Winona, Wabasha, Dakota and Goodhue counties, have their own calendar: catch and release only from January 1 through April 10, 2026; a harvest season from April 11 through September 14 with five trout combined and only one over 16 inches; catch and release from September 15 through October 15; closed from October 16 through December 31; and catch and release again from January 1 through April 9, 2027. Streams inside southeast state parks and city limits are the exception, and the list names Forestville State Park, including the South Branch Root River, and the cities of Chatfield, Lanesboro, Preston, Rushford and Spring Valley: there the water is catch and release from September 15, 2026 through April 9, 2027, so the South Branch through Forestville and the river through Preston and Lanesboro never close.
Three special regulations sit on top of that. On a posted 4.8-mile section of the South Branch inside Forestville State Park every trout from 12 to 16 inches must be released immediately. The Middle Branch is catch and release for its entire length. The South Fork is catch and release, artificials and flies only, on the 7.7 miles from County Road 12 up to its source. Stream trout hours on inland waters run from one hour before sunrise to 11 p.m., one line is allowed on designated trout streams, and live minnows and other live bait are legal on most trout streams unless a stream is listed with a bait restriction. Outside every trout season, fishing designated trout water for any species is prohibited.
Houston after a rain
The Houston record goes back to 1909 and shows a river that lives on runoff more than springs: monthly means of about 460 cfs in January, 550 in February, 1,430 in March, 1,310 in April, 990 in May, 1,130 in June, 920 in July, 760 in August, 690 in September and 620 in October. No shop quotes a wading number for this gauge, so the 400 to 1,000 cfs band on this page is drawn from that record's July-to-February range and describes the main stem, where a smallmouth float is comfortable and a wader can cross a riffle. When Houston jumps past 1,500 after a storm, the South Branch has usually blown out first and will clear first; the Rod Co.'s note that streamers work when the water is up or slightly off-color is the plan for the day after.