There is a magical quality to fall visits to Shenandoah National Park as mile after mile of trees blazing with vivid reds, oranges, and yellows come into view along Skyline Drive. In Rocky Mountain National Park, the aspen groves you see along the lower reaches of Trail Ridge Road turn so vividly gold in the fall that they take your breath away. How fortunate we are that so many national park roads offer fall colors like these as a seasonal bonus. If leaf peeping in the parks is on your to-do list, here are some picks and tips for following the crowd or taking the road less traveled.

There's too much to cover in a single article, so we've divided the parks by general location. Today's article focuses on national parks east of (or along) the Mississippi River. Tomorrow we'll take a look at national parks in the western states and the Ozark Mountains.

Chemistry and Color

Leaves change color in the fall because of some interesting chemical reactions. As an excellent U.S. Forest Service website explains, there are three kinds of chemicals responsible for fall colors:

* Chlorophyll, which gives leaves their basic green color. It is necessary for photosynthesis, the chemical reaction that enables plants to use sunlight to manufacture sugars for their food. Trees in the temperate zones store these sugars for their winter dormant period.

* Carotenoids, which produce yellow, orange, and brown colors in such things as corn, carrots, and daffodils, as well as rutabagas, buttercups, and bananas.

* Anthocyanins, which give color to such familiar things as cranberries, red apples, concord grapes, blueberries, cherries, strawberries, and plums. They are water soluble and appear in the watery liquid of leaf cells.

In a nutshell, this is what happens:

During the growing season, chlorophyll is continually being produced and broken down and leaves appear green. As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids and anthocyanins that are present in the leaf are then unmasked and show their colors.

Since the leaves of different plant species have different chemical compositions, including differing amounts and types of carotenoids and anthocyanins, fall colors occur across a fairly wide spectrum, with certain colors characteristic of particular species.

Oaks turn red, brown, or russet; hickories, golden bronze; aspen and yellow-poplar, golden yellow; dogwood, purplish red; beech, light tan; and sourwood and black tupelo, crimson. Maples differ species by species-red maple turns brilliant scarlet; sugar maple, orange-red; and black maple, glowing yellow. Striped maple becomes almost colorless. Leaves of some species such as the elms simply shrivel up and fall, exhibiting little color other than drab brown.

Don't forget that bushes as well as trees add color to the fall landscape in many areas. Huckleberries, for example, turn a beautiful magenta, maroon or fire red.

Timing is Everything!

The calendar tells the trees and bushes when to change color (diminishing sunlight signals the leaves to stop producing chlorophyll), but weather conditions hugely influence the quality and duration of the color display. Following a warm, wet spring and a typical summer, the best fall colors are produced when autumn days are mild and sunny and evenings are chilly (but not freezing). This said, the onset, duration, and intensity of fall color displays can vary significantly from year to year, and rapidly changing weather conditions can produce dramatic changes in very short order. Wind and rain from a single storm can leave trees bare. Before you head out for your windshield touring, be sure to contact the park or consult other reliable sources for updated information about foliage and road conditions.

The Eastern "Big Four"

East of the Mississippi, the "Big Four" fall foliage magnets are Acadia National Park, Shenandoah National Park, Blue Ridge Parkway, and Great Smoky Mountains National Park. You're certain to have plenty of fall color to enjoy in these places. On the downside, you'll also encounter congested roads, parking problems at crowded overlooks and parking lots, and "no vacancy" signs galore (make your lodging reservations way ahead).

Coastal Maine's Acadia National Park has a mix of evergreens and hardwoods that delight the eye and offer some of the best fall foliage in New England. Many visitors particularly like the bold contrast of the flaming hardwoods, the dark greens of the spruce, fir, and pitch pine, the white bark of the birches, and the blues and greens of the sea. Colors begin to show in the higher and cooler places by late September. If you catch the fall foliage at its peak, which is usually during the first few weeks of October, you can enjoy spectacular views along the Park Loop Road and from the top of 1,530-foot Cadillac Mountain (reachable via a spur). You'll be in for a special treat if you park your car and walk or bike the park's famed carriage roads and enjoy the colors from under the forest canopy. The weather can be surprisingly mild during the leaf peeper season, with afternoon temperatures typically in the high 50s to mid-60s.

The 105 mile-long Skyline Drive, America's first lengthy parkway and the only public road in Virginia's Shenandoah National Park, famously offers a kaleidoscope of red, yellow, and gold each year from about mid-October to mid-November. The rule of thumb is that colors generally peak in Shenandoah during the last half of October. Catching the peak can be tricky, however, since this elongated park is north-south oriented and varies considerably in elevation. Colors make their appearance up to several weeks earlier in the north and at higher and middle elevations (which can be 10-15 degrees cooler than adjacent valleys). The extended season in the south and at lower elevations offers extra options. There are lots of small trees and shrubs like sassafras and sumac that remain vibrant with color after the oaks past their peak. Since oaks tend to shed their leaves late, their cinnamon-colored or rusty-brown leaves can contrast nicely with the abundant evergreen trees and shrubs. If you don't mind the heavier traffic, try to drive at mid-day when sunshine lights the leaves on both sides of the road. If you find the slow traffic too aggravating, and can find a parking place, try one of the park's many excellent trails.

The Blue Ridge Parkway, which winds 469 miles between the southern end of Skyline Drive and the eastern entrance of Great Smoky Mountains National Park, puts on one of the country's best fall colors shows for windshield tourists. You need to be carefully tuned in to the "where and when," though. As in Shenandoah, the leaf peeper season unfolds from north to south and from higher to lower elevations. Depending on location, colors may peak from early October (elevations above 5,000 ft.) to mid-October (3,000-4,000+ ft.) to as late as mid-November (lower elevations near Asheville/Lake Lure). Expect to share the splendor of the brilliant reds, oranges, and yellows with lots of others. On weekends in October, the park's busiest month, it may seem that the whole population of the eastern U.S. has decided to take a leaf peeping drive on the parkway. Travel on weekdays if you can. Gas stations are scarce, so fill your tank before you go.

Straddling the North Carolina/Tennessee border in the Southern Appalachians, Great Smoky Mountains National Park boasts the largest stands of old-growth forest in the eastern United States and the greatest biodiversity of any U.S. park (including 100 or so species of trees). This yields a fall outburst of reds, yellows, purples, browns, and golds rivaling those of the New England countryside. The colors generally peak in mid- to late October at higher elevations (which have a climate similar to New England's), but can start as early as mid-September with the turning of "early" trees like yellow birch, American beech, mountain maple, hobblebush, and pin cherry. At lower and middle elevations, where the color tends to be most spectacular, the blend includes such beauties as sugar maple, scarlet oak, sweetgum, red maple, and hickory. East-west trending Highway 441 (Newfound Gap Road) gets the bulk of the leaf peeping traffic, which is typically quite heavy (especially on weekends), but the Clingmans Dome Road and the Cades Cove Loop are very popular as well. For something different, take the Roaring Fork Motor Nature Trail, a narrow, steep, winding (but paved) one-way road that passes through color-rich forests and offers glimpses of Roaring Fork Creek as a bonus. Try to visit on a weekday or before 10:00 a.m. The park website has links to webcams showing the progression of fall color that sweeps through the Smokies. Always check for road conditions before visiting this park. A paving project will close the Clingmans Dome Road in mid-September. October is a transitional month that can bring foul weather and road closings on short notice. By late October, the park begins reducing visitor center hours and closing some facilities and secondary roads for the winter.

Some "Best of the Rest" Parks to Consider

Since colorful fall foliage is regionally pervasive in the Northeast, the Great Lakes states, and some parts of the South, plenty of other parks -- many within the day-tripper zones of major population centers -- offer good quality windshield touring at the seasonal peaks. The differences between these lesser-publicized fall colors parks and the Big Four are largely a matter of scale. A word of caution is in order. Choosing a Big Four alternative is not necessarily a strategy for avoiding traffic congestion at the seasonal peaks. Leaf peeping attractions that fly below the national radar are well known to local residents and usually receive a good deal of publicity in their respective regions.

Here are a few of the east-of-the-Mississippi national parks that deserve more credit as windshield touring attractions for fall colors enthusiasts.

At Sleeping Bear Dunes National Lakeshore in Michigan's Lower Peninsula, colorful hardwoods abound along the park roads beginning in late September, and peaking in mid- to late October. Sections of the park's Pierce Stocking Scenic Drive are lined with maple, beech, and birch trees that form a gorgeous canopy for windshield touring. Don't forget your camera. The reds and yellows of the maples and beeches vividly contrast with the white birches, and the nearly white dunes and the blue of Lake Michigan provide a dramatic background. As a bonus, this popular scenic drive -- a one-way route with an excellent bike lane -- leads to overlooks requiring only short walks to enjoy magnificent views out over the dunes and the Lake Michigan shoreline.

The West Virginia mountains are loaded with hardwoods and ablaze with color each fall. In New River Gorge National River, the color peaks about the third week of October. The weather is normally mild and dry at that time, so that adds to the appeal. Locals boast that the scenic fall drives on the park roads are on a par with the best.

Minnesota's Mississippi National River and Recreation Area extends 72 miles through the heart of the Minneapolis-St. Paul metro complex. This makes it convenient for thousands of motorists to drive the roads of the riverine corridor and enjoy the fall color displays in the various riverfront parks, historic sites, wildlife areas, and other sites within this unusual park's borders. This is a "partnership" or "cooperative stewardship" park (the National Park Service owns only 62 acres in the 53,775-acre park), so nearly all of the leaf peeping is done on municipal, state, or private land.

At Cumberland Gap National Historical Park, the Pinnacle Overlook (elev. 2,440 ft.) offers spectacular views into mountains and valleys in Kentucky, Virginia, and Tennessee -- and of course the namesake Cumberland Gap. In the fall, this landscape blazes with color and Skyland Road, the winding four-mile route that takes motorists from the visitor center up the mountain to the overlook, is a leaf peeper's delight. Big-rig RVers beware; Skyland Road is closed to vehicles longer than 20 feet.

The Natchez Trace Parkway runs a winding 444 miles from Natchez, Mississippi, across northwest Alabama to the Nashville, Tennessee, vicinity. The cooler northern end of this National Scenic Byway and All-American Road offers the best color, with the reds, oranges, and yellows of its mixed hardwood forest (especially maple, oak, hickory, dogwood, and sumac) usually arriving at their scenic best during mid- to late October. Some of the very best views are to be had at Old Trace Drive (MP 375.8), Metal Ford (MP 382.8), and Swan View Overlook (MP 392.5). Time and weather permitting, take a leisurely stroll to enjoy the foliage at Meriwether Lewis (MP 385.9) or Fall Hollow (MP 391.9). Many motorists from northern states are surprised to find that stretches of the parkway in Alabama and Mississippi offer pleasing color. Among the recommended views in this southerly section are the Freedom Hills Overlook (MP 317.0), the Old Town Overlook (MP 263.9), and the Little Mountain Overlook (Jeff Busby Campground, MP 193.1).

Kentucky's Mammoth Cave National Park offers more than just cave tours. The 52,830-acre park's sprawling upland hardwood forest, interspersed with wide open spaces, is a visual delight in the fall. The Green River Valley landscape offers color-splashed views up to 15 miles.

Be sure to check back with Traveler tomorrow when we'll recommend some fall color tours in national parks west of the Mississippi River and in the Ozarks.