(Backyard Gardener – Photo Illustration – MetroCreativeConnection)
Hello Mid-Ohio Valley farmers and gardeners! The first heavy frost for the area was predicted Thursday night as temperatures might dip to 37 degrees Fahrenheit. Hopefully, backyard gardeners covered any tender annual or warm season vegetables or flowers they want to keep going.
A word of advice on tomatoes. If tomato vines are dead or killed by a frost or freeze, those tomatoes are not safe for canning. The pH, or acidity, changes in this situation to increase the pH above 4.6. Therefore, the safest choice to preserve these affected tomatoes is by freezing or dehydrating.
Unripe, or green, tomatoes can be preserved. However, when canning them they still require acidification. Green tomatoes can be used for relish recipes or can work in garden salsas.
This week I want to talk about the color changes in the leaves of our local trees and shrubs, creating the beautiful spectacle we call fall foliage. Trees that change color in the fall are deciduous trees of course, as our evergreens such as spruce and pine provide us some color in the landscape during winter.
Fall is one of the most beautiful seasons of the year. As you drive throughout the Valley this time of year, you will see the changing of the leaves from green to bold reds, vibrant yellows and bright oranges.
What drives this process is the length of daylight, more specifically increasing darkness over consecutive days and weeks as trees prepare for the dormant season of winter.
Eventually, green chlorophyll in leaves fades away and other leaf pigments like yellow and orange become visible. Depending on where you are in the Mid-Ohio Valley, and what tree species are involved, we normally expect this color display from late September through October.
Three factors which cause the tree leaves to change color this time of year include daylength, leaf pigments and weather. Daylength is the only constant of these three. Following the summer solstice in June, daylight shortens in the Northern Hemisphere and the nights become longer.? The decreasing daylight?triggers certain reactions in trees and leaves.
Let’s get down to brass tacks. 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 differences in fall color from species to species.
The weather absolutely affects the amount, duration and brilliance of autumn color that occur before and during the time chlorophyll is declining in the leaves. Temperature, light and water supply are the primary factors that influence the synthesis of carbohydrates (sugars) that favors anthocyanin formation and bright fall color.
Cool, but not freezing, temperatures favor anthocyanin production. Early frost is more likely to kill leaves, making them turn brown and fall sooner from the trees. Bright light favors red colors, so red color often develops on exposed leaves.
Water supply also affects anthocyanin production, with mild drought favoring bright reds. Rainy days occurring near peak coloration will decrease color intensity. Late summer droughts can delay the onset of fall color by a few weeks.
Temperature, sunlight and moisture are highly variable each year. This means no two autumns are alike, which is really amazing. Even individual trees of the same species growing together often show differences in leaf color because of variations in the amount of sugars in the leaves and genetic predisposition. Some reach their peak color earlier than others.
Variations among species in the rate of color change reflect differences in chlorophyll breakdown, production of anthocyanin and exposure of carotene and xanthophyll.
Many species of trees display beautiful fall foliage. Many of our maples (Acer) have wonderful leaf color in fall. Freeman maples are examples of shade trees with excellent fall foliage. 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 has cultivars such as “Red Sunset,” “Redpointe” and “Scarlet Jewell” that have dark red foliage in fall.
Sugar maple, the state tree of West Virginia, exhibits fall foliage which may vary from yellow to orange to reddish-orange. “Commemoration,” “Legacy” and “Fall Fiesta” are excellent recommended sugar maple cultivars.
Don’t forget about the oaks (Quercus). In fall, the foliage of white oaks is often reddish brown and red oaks exhibit wine-red foliage.
Additional trees with colorful fall foliage are yellowwood (Cladrastis kentukea), honey locust (Gleditsia triacanthos) and black gum (Nyssa sylvatica). The ginkgo (Ginkgo biloba) also possess outstanding fall foliage.
Small trees with colorful fall foliage include serviceberry (Amelanchier spp,) American hornbeam (Carpinus caroliniana) and the Eastern 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.
Several deciduous shrubs have colorful fall foliage. Common witch hazel (Hamamelis virginiana) has yellow leaves in the fall. 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.
Fall foliage season will end when fall winds and rains in late October and early November finally remove leaves from the trees. Biologically, this is due to the creation of the abscission layer between the twig and the leaf itself. This layer of cells is weak and can’t hold on to the leaves, allowing leaves to be blown from trees during wind and heavy rains.
The process that allows leaves that were once holding tight during summer months to suddenly fly free happens because the leaf no longer needs to take up nutrients and water or send back sugars and starches into the tree.
Contact me at the Wood County WVU Extension Office 304-424-1960 or e-mail me at jj.barrett@mail.wvu.edu with questions. Good Luck and until next time Happy Gardening!
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