Already the sumac and ferns and black ash are turning color, along with a handful of maples popping here and there.

As days shorten and nights cool down, the Northland’s leafy forests are making their annual turn toward dormancy, a process — called senescence — that will entertain us for the next month or more.

Barring any major wind or rain storms, forest experts are predicting a good fall color season thanks to just enough rain across northern Minnesota and few insect or disease problems.

“Except for a few areas of the state that saw too much water, it’s shaping up to be a perfect fall for colors," said Val Cervenka, forest health program coordinator for the Minnesota Department of Natural Resources. “Fall should be going out in a blaze of color glory.”

The exceptions are some parts of the Twin Cities and southeastern Minnesota where flooding and standing water may have submerged tree roots too long. That stresses and can even kill trees and will likely impact fall color, Cervenka said. That includes the Twin Cities’ Fort Snelling State Park which remains closed because of prolonged flooding this summer.

“Most everyone else had at least adequate rainfall. It was drier north of Duluth, but it wasn’t a drought. … Healthy trees going into fall are the biggest factor in what kid of color we should expect," Cervenka said. “After that, it’s takes getting some chilly nights, not too much frost, but maybe a light frost, and then not too much warmth as the colors emerge.”

One color that will be less visible on the northern Minnesota landscape again this year is the deep gold of tamarack needles. Tamaracks are the swamp- and bog-bound "evergreens" in summer with needles that turn yellow-gold and fall off in autumn. But Minnesota has lost more than a half-million acres of tamarack over the last 20 years due to a prolonged infestation of eastern larch beetles. That includes 180,000 acres impacted in 2018 alone. Tamarack often are the latest trees to hit peak color in late October or early November.

"Tamaracks are still dying from the beetle, or the larvae actually," Cervenka said. "People are going to notice gray hues instead of gold in those spots."

The problem is climate change, she said. Larch beetles are now producing two generations per summer, thanks to warmer temperatures earlier and later in the season, where in the past it had always been one generation. The extra stress of a second attack in one summer is too much for many tamarack to handle, and they die. Cervenka said it remains unclear what other trees, if any, might take tamarack's place in the boggy ecosystems they favor.

The onset of fall color is triggered by shortening daylight hours and the impact that change has on the chemistry of leaves. That’s why the process starts at nearly the same time every year. But temperature also plays a role, and cooler nights help bring out more color. It's that combination of shorter days, but especially the colder temperatures, that cause the change in hormones in the leaf that trigger senescence, the breakdown of cells and the color change. An unusually warm fall can slow things down, Cervenka and others note. Experts say a light frost at the start of the color season actually helps produce vivid color. But a hard frost, down into the lower 20s, can kill color fast. And of course a huge wind or rainstorm as peak color approaches can ruin everything.

Chlorophyll gives leaves their green color, while anthocyanins, carotenoids and tannins produce the reds, golds and browns that come to the forefront in the fall, the DNR notes. Those shorter periods of daylight mean a closing off of the leaf veins that carry liquid sugar in and out of leaves. Sugars in the leaf permit the red and purple colors to develop.

Purple-like and red pigments are found in the leaves of maple and oak, some varieties of ash, and tall shrubs like cherry, sumac and viburnum. Yellow is always present in leaves all summer long, but the color is revealed when the green pigment in chlorophyll breaks down.

More recent research also shows that leaves have evolved to develop those bright colors as a sort of sunscreen against damage as the tree goes dormant, protecting the leaf as long as possible so the tree can keep drawing nutrients until the leaves fall off.

Naturalists remind folks to look down, not just up, to see bountiful fall color among grasses, wildflowers and ferns. And they have another suggestion you may have overlooked: If you want to see more color, look for hilly areas, and not just because you get longer vistas. In general there's more variety, more tree species, in hilly areas. Flat areas generally tend to have fewer or even a single species. The more species, the better the chance you'll see one or more at its peak color at any one time.

As happens each year, some individual turn started turning color in August. But very early coloring is a sign of unhealthy trees, not an early autumn or winter. Trees can't predict what weather is coming. They can only react to conditions they have already experienced. That early color you saw in places was likely caused by drought, stress, insects, disease or disturbances such as nearby construction or traffic.

Explore Minnesota, the state’s tourism bureau, said its survey of 300 tourism businesses showed summer revenue was up for 49% while occupancy was up for 42% of respondents compared to summer 2018. By comparison, 24% of respondents said revenue was down, and 26% reported decreased summer occupancy.

And businesses also said they expect a strong fall travel season, which now accounts for 25 percent of all state tourism spending — or more than $3.8 billion during fall color season.

The numbers belay a strong economy, said John Edman, director of Explore Minnesota, in releasing the survey results. And more people are spending more time and money traveling during fall than ever before. Many businesses and communities hold special events timed for peak color.

"Many travelers consider fall to be their favorite season. Smaller crowds, cooler temperatures and beautiful fall colors make it an ideal time to get away," said Erica Wacker, communications manager at Explore Minnesota. "Destinations throughout the state cater to fall crowds with seasonal festivals, fall color cruises, Oktoberfest celebrations, running and bike races, art studio tours, and other fun for the whole family."

The Minnesota DNR will again offer weekly fall color updates each Thursday starting this week from state parks across the state. Go to dnr.state.mn.us/fall_colors . For information on fall color status in Wisconsin, go to travelwisconsin.com/fall-color-report .

Six Northland fall color tours to try

Ok this may be Minnesota's most famous and popular scenic drive, especially in autumn, and you will have to fight the crowds on weekends both for prime parking spots and places to stay. There isn't much of a shoulder season on the North Shore any more. That said, the vistas from Highway 61 afford great views of yellow aspen and birch along the shoreline with Lake Superior as an impressive backdrop. But make sure you get up and away from the lake, on the backside of the Sawtooth Mountains, to see huge expanses of red and yellow maples. Those maples will likely peak Sep. 21-28, earlier than the North Shore itself which may not peak until early October. Best maple views are found on gravel Superior National Forest roads off Highway 1, the Caribou Trail, Sawbill Trail, Gunflint Trail and Arrowhead Trail - but any road that goes inland several miles from Lake Superior will probably get you to some oohs and ahhs.

U.S. Highway 169 from Virginia to Tower, Minnesota Highway 135 through Biwabik back to Virginia

This area will peak from mid September to early October. There’s also lots of other things to do, form major golf courses to the Mesabi Trail bike route to fishing on Lake Vermilion. A side trip up to Ely and Bear Head Lake State Park along the way will provide even more color.

Minnesota Highway 38 from Grand Rapids to Bigfork and back on Itasca County Road 7.

This area peaks in late September to early October. This super scenic byway winds over hills through the colorful mix of pine and hardwoods of Chippewa National Forest. Return via County Road. 7 and make a side trip to beautiful Scenic State Park. Or take one of the back roads through the forest, with stops at lakes and hiking trails along the way.

U.S. Highway 71 between Park Rapids and Bemidji. Itasca State Park, the source of the mighty Mississippi River, is the star attraction on this route. Lake Bemidji State Park, with its birch and pine, is another highlight. There's a paved bike trail in Itasca, and mountain bike trails in Bemidji State Park. You'll also find scenic biking along the nearby Heartland Trail. (To get over to this area, take Minnesota Highway 200 from west of Floodwood through Remer and into Walker, with long stretches of maple along the way.)

Minnesota highways 371 and 6, Plus U.S. Highway 169 and adjacent county roads.

Bring your bikes and ride the Paul Bunyan trail. Famous Gull, Pelican and Cross lakes and the Whitefish Chain of Lakes sparkle amid woods of maple, oak, birch and aspen. Mille Lacs Kathio State Park is an expanse of colorful forest at the edge of Mille Lacs, and an observation tower here offers fantastic views.

Drive Highway 13 up the South Shore of Lake Superior to Bayfield, with plenty of places to stop, eat and hike along the way. Continue on through Washburn to Ashland then return on U.S. Highway 2 through appropriately named Maple. Side trips — driving, biking, hiking or canoeing — along the Brule River are worth the effort. The Bayfield Apple Festival draws huge crowds but offers a fun destination reason to a fall color trip at near peak color, Oct. 4-6.