Mario Bautista
Learn how the colors of fall form in your favorite plants
As autumn approaches, deciduous trees and shrubs transform into a vibrant mix of reds, oranges and yellows. Fall color in plants is not only beautiful but a fascinating interplay of pigments, environmental factors and seasonal changes. In this article, horticulturists with Iowa State University Extension and Outreach answer questions about how fall color forms and recommend trees and shrubs with colorful fall foliage to plant in the home landscape. (photo by ISU Extension)
AMES, Iowa — As autumn approaches, deciduous trees and shrubs transform into a vibrant mix of reds, oranges and yellows. Fall color in plants is not only beautiful but a fascinating interplay of pigments, environmental factors and seasonal changes. In this article, horticulturists with Iowa State University Extension and Outreach answer questions about how fall color forms and recommend trees and shrubs with colorful fall foliage to plant in the home landscape.
How does fall color develop in trees and shrubs?
Fall color in leaves is driven by three pigments: chlorophyll, carotenoids and anthocyanins. Weather conditions influence what happens with each of these pigments.
Chlorophyll, the green pigment, is crucial for photosynthesis and is dominant during the growing season. In the fall, the day length shortens and temperatures cool, which triggers plants to prepare for winter by reducing chlorophyll production and restricting carbohydrate movement to the leaves.
Carotenoids are always present in the leaves but are masked by chlorophyll. When chlorophyll production stops, the green color fades, revealing the yellow and orange hues of carotenoids.
Anthocyanins, which give red and purple colors, are produced in late summer and early fall when carbohydrate transport is restricted. Environmental factors like warm days and cool nights enhance anthocyanin production, leading to vibrant colors.
Not every tree or shrub species produces carotenoids or anthocyanins in equal quantities. This is what creates the difference in fall color from species to species.
Why does fall leaf color on trees and shrubs vary from year to year?
The weather in early fall largely determines the intensity and duration of leaf color in those tree and shrub species capable of producing good fall color. The best fall color typically develops when days in early fall are sunny and mild, and nights are cool but remain above freezing. Long periods of cloudy, rainy weather or a hard freeze in early fall will mute fall colors.
Which trees have colorful fall foliage?
Shade trees with excellent fall foliage include Freeman maple (Acer × freemanii). They are hybrids of red and silver maples with leaves that vary from orange to red in fall. Popular Freeman maples include Autumn Blaze®, Sienna Glen® and Firefall™. Red maple (Acer rubrum) has cultivars such as Red Sunset®, Redpointe™, and Scarlet Jewell™ that have dark red foliage in fall.
Sugar maple (Acer saccharum) is native to eastern Iowa. Their fall foliage varies from yellow to orange to reddish-orange. ‘Commemoration,’ ‘Legacy’ and Fall Fiesta™ are excellent sugar maple cultivars. The fall foliage of black maples (Acer nigrum) varies from yellow to orange. In fall, the foliage of white oaks (Quercus alba) is often reddish brown, while red oaks (Quercus rubra) have wine-red foliage. Black gums (Nyssa sylvatica) are not widely grown in Iowa. However, they possess outstanding fall foliage.
Additional trees include yellowwood (Cladrastis kentukea), honeylocust (Gleditsia triacanthos var. inermis) and ginkgo (Ginkgo biloba), including cultivars ‘Autumn Gold’ and Presidential Gold®, all with yellow fall color. Other fall favorites include ‘Moraine’ sweet gum (Liquidambar styraciflua ‘Moraine’) with foliage that varies from yellow to red to purple and Dutch elm disease-resistant American elms (Ulmus americana), such as ‘Jefferson,’ ‘Princeton’ and ‘Valley Forge,’ with yellow fall foliage.
Small trees with colorful fall foliage include serviceberry (Amelanchier × grandiflora), American hornbeam (Carpinus caroliniana) and redbud (Cercis canadensis). The fall foliage of serviceberry and American hornbeam varies from yellow to orange to red, while redbud leaves turn yellow in fall.
Which shrubs have good fall color?
Several deciduous shrubs have colorful fall foliage. The fall foliage of fothergilla (Fothergilla spp.) varies from yellow to orange to red. Common witch hazel (Hamamelis virginiana) has yellow leaves in the fall. In autumn, the foliage of Virginia sweetspire (Itea virginica) varies from yellow to orange to reddish purple. Spicebush (Lindera benzoin), staghorn sumac (Rhus typhina) and black haw viburnum (Viburnum prunifolium) have yellow, red and reddish purple foliage, respectively.
Do any perennials have colorful fall foliage?
Most perennials are grown for their attractive flowers. However, several perennials have colorful fall foliage.
Perennials with yellow foliage in fall include the blue star (Amsonia spp.), balloon flower (Platycodon spp.), hosta (Hosta spp.) and monkshood (Aconitum spp.). The sensitive fern (Onoclea sensibilis) and royal fern (Osmunda regalis) also develop yellow fall color. The foliage of pigsqueak (Bergenia cordifolia) often turns burgundy red in fall. The foliage of many hardy geraniums (Geranium spp.) is yellow, orange, red or purple in autumn.
Several ornamental grasses also have striking fall color. Switchgrass (Panicum spp.) cultivars with colorful fall foliage include ‘Rehbraun’ (reddish brown), ‘Rotstrahlbusch’ (burgundy red) and ‘Prairie Fire’ (wine red). In fall, Miscanthus cultivars ‘Purpurascens’ and ‘November Sunset’ have orange-red and golden-orange foliage, respectively. Little bluestem (Schizachyrium scoparium) has yellow to burnt orange fall color. The little bluestem cultivar ‘Blaze’ has an orange to reddish-purple fall color, while ‘Blue Heaven’ develops a burgundy-red color in autumn.
–ISU Extension
