Autumn marks the transition of hot summer days to cooler temperatures and sometimes vibrant leaf color. Texas is an underrated leaf peeping destination with multiple parks focused on hardwood forest conservation.
Texas leaf peeping
A trip to the pine and hardwood forests of East Texas during October and November may display beautiful fall foliage. Or if you want to explore Central and West Texas, consider visiting the Lost Maples State Natural Area, a genetically distinct population of Bigtooth Maples (Acer grandidentatum) which was geographically isolated during the last glacial period.
View Texas fall foliage and wildflower routes on Texas Scenic Views.
Types of leaf pigment
Trees show individual variation in leaf color. This is due to the tree’s response to environmental factors and different mixtures of chlorophyll, carotenes, xanthophylls, and anthocyanin pigments that produce the red, orange, yellow, crimson, purple, and related colors in the leaves.
Water and heat stress (hot, dry weather) and cool temperatures (autumn) will destroy chlorophyll and allow carotenes and xanthophylls to be exposed. In most plants there are about three times as much chlorophyll as carotenes and xanthophylls.
Chlorophyll
Chlorophyll is what gives plants their green color. Tree leaves have other colors present most of the time, but the green chlorophyll is so dominant that it masks the other colors. Near the end of the growing season (autumn), chlorophyll production is reduced or stops and chlorophyll that is present in the leaves begins to break down.
Anthocyanin
Anthocyanin is a pigment responsible for the red, pink, and purple colors in leaves. It forms in the sap of leaf cells, usually late in the growing season (autumn). Its formation is dependent on an accumulation of carbohydrates in the plant, on the genetic properties of the tree, and environmental factors.
Texas tree species that have anthocyanins include:
- Sassafras (Sassafras albidum)
- Sweetgum (Liquidambar styraciflua)
- Bigtooth maples (Acer grandidentatum)
- Red oaks (section Lobatae)
- Tupelo (Nyssa sylvatica)
- Sumac (Rhus lanceolata).
Carotenoids
Some trees do not form anthocyanin pigments, but carotenoids. When a leaf’s chlorophyll declines in the fall, the orange carotenes and yellow xanthophylls become visible.
Carotenes
Carotenes are a subcategory of carotenoids that produce red, orange and occasionally yellow pigments.
Texas tree species that have high levels of carotenes include:
Xanthophyll
Xanthophyll is a subcategory of carotenoids, typically yellow and orange pigments. However, red, pink, and purple pigments may also develop.
Texas tree species that have high levels of xanthophylls include:
Tannins
Tannis are compounds responsible for bitter, astringent flavors typically found in unripe fruit and wine. Tannins found in wine are transferred through wood barrels from tree species that have high amounts of tannic acid. They are also responsible for brown colors in oak leaves.
Texas trees that have high levels of tannins are:
- Oaks (Quercus spp.)
- Honey mesquite (Prosopis glandulosa var. glandulosa)
- Screwbean mesquite (Prosopis pubescens).
Color changing factors
Chlorophyll formation is sensitive to any factor that disturbs metabolic processes in the plant. Unfavorable levels of light, temperature, water, oxygen, and essential minerals will impact how much chlorophyll a plant produces.
The most important environmental factors controlling fall foliage are temperature, light, and water.
Cool temperatures (above freezing), drought, and bright sunny days favor the production of anthocyanin. Because they are exposed to the most sunlight, leaves in the upper crown usually develop the brightest red colors.
However, several days of rainy or cloudy weather often decrease the intensity of fall colors. The bright red and orange fall colors maple trees are famous for are due to the production of anthocyanin in the leaves.
When a plant is lacking in nitrogen or iron (mineral deficiencies), or is grown in little or no light, it will develop a yellow or pale green color because it lacks chlorophyll.
Leaf color change & genetic mutations
Sometimes a genetic mutation in the plant will cause leaves to be variegated (part yellow and part green). The part of the leaf that is yellow lacks chlorophyll. Occasionally a mutation will occur where no chlorophyll is produced and a short-lived albino plant results.
Sometimes bud mutations occur resulting in albino or variegated branches in otherwise normal (green) trees and shrubs. These color variations are not associated with fall leaf colors, but involve green and yellow pigments in the leaves.
Learn more
Read fall foliage – explained.
Explore the science and art of plant pigments through hands on learning experiences.
We’ve partnered with Project Learning Tree and Texas Forestry Association to develop “Signs of Fall”, an activity that utilizes common household or classroom materials to do chromatography. Request more information regarding Project Learning Workshops in Texas.
If you’re outside of Texas and interested in a hands-on activity with clear instructions, check out Science Buddies’ Find the Hidden Colors of Leaves classroom resource.
Cornell University Cooperative Extension has developed a Natural Plant Dye Activity as a real-life, practical application of chromatography and plant chemistry.
Article source and photo credit: Texas A&M Forestry Service
