WISCONSIN RAPIDS, Wis. >> “The most picturesque time of year on a cranberry farm is during fall harvest with the seemingly endless sea of red floating cranberries,” said Steve Bartling, a grower in Manitowish Waters.

The rest of the year? Forget about it.

Many people think cranberries grow in water, Bartling said. Not so. Berries form on perennial vines in thick mats on the ground and turn red only in the fall. That’s when farmers flood the marshes so they float to the surface.

During that short window of time, usually late September through mid-October, visitors head for central and northern Wisconsin to watch machines comb through vines and workers in hip waders corral the just-plucked crimson fruit onto conveyor belts.

Drive up to Wisconsin Rapids and take a DIY tour along the Cranberry Highway, winding almost 50 miles along country roads skirting cranberry farms, some in the same family for three or four generations. You’ll see trucks being loaded with berries bound for your Thanksgiving table or that cocktail you might sip before dinner.

Gawking from the roadside has limitations. For a closer look — and an education in Wisconsin’s state fruit — take a guided tour of a marsh. There are plenty to choose from. Wisconsin grows more than 60 percent of the U.S. cranberry crop and has enough cranberry farms to cover the entire city of Chicago and a few suburbs, too. Only a few acres flood, though. The rest is support land: wetlands, woodlands and such.

Bartling’s Manitowish Cranberry Co. gives tours to groups and will join other growers in sponsoring chamber of commerce public marsh tours offered free on Friday mornings through Oct. 6. In Eagle River, Lake Nokomis Cranberries offers free marsh tours Monday through Saturday during harvest. It has a gift shop and winery offering tastings of cranberry wine.

You can don waders and step into a flooded marsh on Harvest Day, Oct. 7, at Wetherby Cranberry Co. in Warrens. Members of the farm’s family guide the morning tours costing $5 or $15 if you choose to wade.

Support students at Pittsville High School by taking its Splash of Red marsh tours. Members of the cranberry science class and Future Farmers of America club lead the outings Wednesdays and Fridays in October. The $20 tour lasts about 2-1/2 hours and includes a cranberry-­centric lunch back at the school in Pittsville.

A free marsh tour comes with a stay in the one-bedroom Stone Cottage at Glacial Lake Cranberries about 15 miles west of Wisconsin Rapids. Mary Brown, third-generation owner of the farm, is a walking cranberry encyclopedia. If you want to know why cranberries are Wisconsin’s largest fruit crop, she’ll tell you about the sandy, acidic soil — perfect for growing cranberries — left behind here when lakes formed by glaciers receded. A high water table and wetlands help farmers direct water into ditches to flood the cranberry beds. Brown recently launched a business producing dried cranberries with no added sugar. Honestly Cranberry offers a natural alternative to the sweet snacks on many store shelves.

At four Wisconsin cranberry festivals, marsh tours are part of the fun.

The Warrens Cranberry Festival in the self-­proclaimed “Cranberry Capital of the World” includes a long parade of horses, automobiles, tractors and floats. Visitors browse more than 1,300 booths and see all sorts of contests: pie-eating, scarecrow, quilt and needlework. The festival usually draws 120,000 people. Because of the size of the crowd, it is scheduled for Sept. 22-24, before the busy cranberry harvest often begins. Its marsh tours may be too early for viewing flooded cranberry beds, but visitors see other work on the farms.

In northern Wisconsin two festivals on Oct. 7 include marsh tours. At the Stone Lake Cranberry Festival in Stone Lake, you can start the day with a pancake cranberry breakfast. Cran-A-Rama in Manitowish Waters offers pontoon boat cruises.

Marsh tours begin two days before the official opening of the Eagle River Cranberry Fest and continue through the weekend event, Oct. 7 and 8. Check out the Make-a-Wish Foundation’s world’s largest cranberry cheesecake. Runners burn off calories in the Berry Bog 5K Jog.

At the Wisconsin Cranberry Discovery Center, open daily spring through fall in Warrens, you’ll find out why cranberries float and how they got their name. Along with exhibits loaded with cranberry facts, the center has a taste test kitchen and ice cream parlor. Pick up or download some recipes for the coming cranberry onslaught. About 20 percent of Wisconsin’s harvest is consumed during the Thanksgiving and Christmas holidays.