Deep autumn is settling in. The last days of late afternoon sun lights the still hanging leaves like bits of stained glass.
The shades of red, yellow, oranges and golds shift and intensify in the coolness of the season.
The rains of late, late autumn will bring the leaves down off the trees. One windy storm can beat the trees bare.
Overall, I think there is less fall color along city and suburban streets. And there seems one main reason for this, humans in these areas are planting fewer native trees.
Native Trees
It is mostly native trees which provide the fall color. Fewer than two dozen common and widespread native species are responsible for the fall extravaganza. List of Native Trees for Philadelphia (Street Trees)
Across the North American continent perhaps 100 native woody species provide the colorful leaf changes that so delights the eye.
Oaks, maples, birches, hickories, ashes, gums, Sycamore, Tulip poplar and dogwoods provide most of the fall color in the North American forests and woodlands.
There are local indigenous species of each of these trees in most temperate areas of North America. There is are color changing species for nearly everyone.
Colors of the Leaves
Here in Philadelphia, Oaks (White, Scarlet, Red and Black) provide reds and browns. Sugar Maples, Tulip poplars and Redbuds give luscious yellows. Dogwoods display deep maroons.
In gardens and along streets humans often chose plants because they stay green in the winter. This also means they stay green in the fall, too.
The vine English Ivy stays green all year-long. The native vine Virginia Creeper (Parthenocissus quinquefolia) has shades of red and maroon leaves.
The native woody species of trees, shrubs and vines are adapted to the onset of winter dormancy signaled by drier weather, less daylight and cooler temperatures. This is why leaves change colors in the fall.
Are we destroying the brilliant autumn leaf-changing event of the Eastern part of North America by planting non-native trees, shrubs and vines?
Autumn in the Natural World, Available in pdf and paperback
Excerpt from Plants in Autumn section
Little plant growth takes place at soil temperatures below 40 degrees Fahrenheit (4 degrees Celsius). For plants to grow well the soil temperatures need to be between 40 degrees (4 degrees Celsius) and 100 degrees Fahrenheit (37 degrees Celsius). Spring planted flowers take longer to mature than summer planted flowers. Spring planted flowers will take 60 to 90 days to mature. Summer planted flowers will take 45 to 60 days to mature. Late summer planted flowers (around July 1st) will take 90 and 120 days to bloom as the air temperatures cool.
Available as a downloadable pdf and paperback on Lulu.com. Read about the book here.