Elephant jokes are timeless, and here’s a classic. How does an elephant get down from a tree? It sits on a leaf and waits until autumn.

Ask anyone to picture autumn, and colorful fall foliage probably come to mind. Autumn has a special ambience, and we can thank trees and shrubs for giving us a classic fall feature.

Why do leaves change color? When foliage starts its yearly transformation, we might assume cooler temperatures are responsible because they arrive about the same time. But temperature isn’t the first trigger of fall color — shorter days are. Plants sense the decreasing daylengths of autumn, and begin preparing for winter. Green chlorophyll in leaves breaks down, revealing pigments that were previously masked, mostly yellow and gold.

Chelone, commonly called turtlehead, is a colorful fall blooming perennial. David Samson / The Forum
Chelone, commonly called turtlehead, is a colorful fall blooming perennial. David Samson / The Forum

Besides the uncovering of yellow tones, which accounts for the golden fall color of some trees and shrubs, other species go a step further and produce red, orange and scarlet colors by their leaf chemistry. When night temperatures drop below about 45 degrees, sugars are trapped within these leaves and chemical reactions convert the sugars into red and purple pigments.

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The most spectacular fall colors follow a succession of warm, sunny days and cool, crisp, non-freezing nights. Frost isn’t needed and does more harm than good because it makes leaves drop faster, ending the show.

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For three seasons of color, plan new landscapes to include fall color favorites. Even established plantings usually have room to add shrubs, small-scale trees or perennial flowers that light up the yard in autumn.

The following are some well-adapted favorites.

Annual alyssum and dianthus continue blooming even after frost. David Samson / The Forum
Annual alyssum and dianthus continue blooming even after frost. David Samson / The Forum

Larger-scale trees

Dakota Pinnacle birch (yellow), Prairie Dream birch (yellow), Northern Tribute River birch (yellow), Northern Acclaim honey locust (yellow), Prairie Torch buckeye (orange-red), LavaBurst buckeye (orange-red), Autumn Splendor buckeye (orange-red), Prairie Stature oak (red), Prairie Expedition elm (yellow), Northern Flare sugar maple (orange red), Northern Red oak (red), Prairie Sky poplar (yellow), hackberry (light yellow), larch (golden yellow), Autumn Blaze maple (red) and Firefall maple (scarlet).

(Note: Autumn Blaze and Firefall maples are highly susceptible to iron deficiency chlorosis, and are often not the best choice for heavy clay soil.)

Smaller-scale trees

Flame Amur maple (red), Prairie Horizon alder (yellow), Prairie Radiance euonymus(red), Quaking aspen (yellow), Prairie Gold aspen (golden yellow), Canada Red cherry (purple in summer, red mix in fall), Juneberry (gold and scarlet) and Hot Wings Tatarian maple (scarlet).

Shrubs

Fireworks Amur maple (scarlet red), Carousel barberry (red), Rosy Glow barberry (purple in summer, red mix in fall), winged euonymus burning bush (bright scarlet), cotoneaster (orange red), Alaska viburnum (red), Gary viburnum (red), sumac (scarlet), gooseberry (copper orange), Siberian Pearls dogwood (purple red), Summer Wine ninebark (purple in summer, red mix in fall), Cotton Candy smokebush (scarlet) and Amber Jubilee ninebark (copper mix).

Perennial flowers for fall bloom

Chrysanthemums (Minn and Mammoth series), tall sedums (Autumn Joy, Neon, Pure Joy and Maestro), ornamental grasses, coneflower, rudbeckia, chelone, asters (Purple Dome and others) and ironweed.

Winter-hardy mums, like the Mammoth series, are spectacular fall blooming perennials. David Samson / The Forum
Winter-hardy mums, like the Mammoth series, are spectacular fall blooming perennials. David Samson / The Forum

Annuals for fall flowering

Alyssum, ornamental kale, dianthus, dusty miller, fountain grass, viola and pansy.

Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at donald.kinzler@ndsu.edu or call 701-241-5707.