Warm fall days with cool nights should produce the most brilliant fall colors.

The lush, sometimes subtle colors of the summertime pinks and purples are slowly being replaced with the vibrant reds and various shades of yellow and golden. I started noticing fall color with the vibrant red of a maple tree in our neighborhood and realized it is time to open my eyes wider as I do my errands. The old folklore was that there had to be a hard frost to bring the color. Obviously that doesn’t ring true as our night temperatures have generally been in the 40s with some nights dipping into the 30s, but not a hard frost. You have to stop and wonder what does make the dramatic color change in deciduous trees and shrubs. The green we see in leaves is chlorophyll, the pigment that absorbs sunlight. As days shorten and nights become crisper the chlorophyll cells break down and other pigments in the leaf structure take over. According to a U.S. Forest Service paper, temperature and moisture are the main influences. A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring out the most spectacular color. During these days, lots of sugars are produced in the leaf but the cool nights and the gradual closing of the veins going into the leaf prevents these sugars from moving out. These conditions, lots of sugar and lots of light spur production of the brilliant anthocyanin pigments. It’s not your imagination that in some years the fall color seems more intense than in other years. The amount of moisture in the soil also affects autumn colors. Soil moisture varies greatly from year to year. A late spring or a severe summer drought can delay the onset of fall color by a few weeks. A warm period (both day and night) during the fall will also lower the intensity of fall colors. A warm wet spring, favorable summer weather, and warm fall days with cool nights should produce the most brilliant fall colors. The East Coast area is famous for the spectacular autumn colors. Adirondack, Appalachian, Smoky and Rocky Mountains are also noted for colorful displays of reds, oranges and golds. In the West we see the bright yellows of aspen stands and western larch (commonly called tamaracks in eastern North America) contrasting with the dark green of evergreen conifers and the blue-green of the junipers. As the days become shorter and the intensity of sunlight declines, leaves begin the processes leading up to their fall. The veins that carry fluids into and out of the leaf gradually close off as a layer of cells form at the base of each leaf. These clogged veins trap sugars in the leaf and promote production of anthocyanins. Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall. Then it is time to get out the rake and find a temporary home for the leaves until it is time to mulch. Mulching should be done after the first hard freeze. If applied earlier you trap heat in the ground and risk bulbs starting to develop or spring growth of perennials starting to pop through. If you decide your landscape needs a fall color punch, spend some hours this winter doing research. Plan where you would plant; consider the water source, plant hardiness, site location, the maximum growth of the tree or shrub. Funny how that cute little tree or shrub turns into a monster over the years. You might also want to consider if the plant material will give you several seasons of enjoyment, a spring flower, the possibility of berries or interesting seed pods, plus fall color. Purchase plants appropriate for our growing climate which range from USDA Zone 2 to Zone 5. Our local nurseries have many selections and the best part is that the materials have been hardened off and are acclimated to our climate. Check out OSU

publications

: Fire-Resistant Plants for Home Landscapes and Water-wise Gardening in Central Oregon, at extension.oregonstate.edu/deschutes for suggestions.

The lush, sometimes subtle colors of the summertime pinks and purples are slowly being replaced with the vibrant reds and various shades of yellow and golden. I started noticing fall color with the vibrant red of a maple tree in our neighborhood and realized it is time to open my eyes wider as I do my errands.

The old folklore was that there had to be a hard frost to bring the color. Obviously that doesn’t ring true as our night temperatures have generally been in the 40s with some nights dipping into the 30s, but not a hard frost. You have to stop and wonder what does make the dramatic color change in deciduous trees and shrubs.

The green we see in leaves is chlorophyll, the pigment that absorbs sunlight. As days shorten and nights become crisper the chlorophyll cells break down and other pigments in the leaf structure take over.

According to a U.S. Forest Service paper, temperature and moisture are the main influences. A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring out the most spectacular color. During these days, lots of sugars are produced in the leaf but the cool nights and the gradual closing of the veins going into the leaf prevents these sugars from moving out. These conditions, lots of sugar and lots of light spur production of the brilliant anthocyanin pigments.

It’s not your imagination that in some years the fall color seems more intense than in other years.

The amount of moisture in the soil also affects autumn colors. Soil moisture varies greatly from year to year. A late spring or a severe summer drought can delay the onset of fall color by a few weeks. A warm period (both day and night) during the fall will also lower the intensity of fall colors. A warm wet spring, favorable summer weather, and warm fall days with cool nights should produce the most brilliant fall colors.

The East Coast area is famous for the spectacular autumn colors. Adirondack, Appalachian, Smoky and Rocky Mountains are also noted for colorful displays of reds, oranges and golds. In the West we see the bright yellows of aspen stands and western larch (commonly called tamaracks in eastern North America) contrasting with the dark green of evergreen conifers and the blue-green of the junipers.

As the days become shorter and the intensity of sunlight declines, leaves begin the processes leading up to their fall. The veins that carry fluids into and out of the leaf gradually close off as a layer of cells form at the base of each leaf. These clogged veins trap sugars in the leaf and promote production of anthocyanins.

Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall. Then it is time to get out the rake and find a temporary home for the leaves until it is time to mulch.

Mulching should be done after the first hard freeze. If applied earlier you trap heat in the ground and risk bulbs starting to develop or spring growth of perennials starting to pop through.

If you decide your landscape needs a fall color punch, spend some hours this winter doing research. Plan where you would plant; consider the water source, plant hardiness, site location, the maximum growth of the tree or shrub.

Funny how that cute little tree or shrub turns into a monster over the years. You might also want to consider if the plant material will give you several seasons of enjoyment, a spring flower, the possibility of berries or interesting seed pods, plus fall color. Purchase plants appropriate for our growing climate which range from USDA Zone 2 to Zone 5.

Our local nurseries have many selections and the best part is that the materials have been hardened off and are acclimated to our climate.

Check out OSU publications: Fire-Resistant Plants for Home Landscapes and Water-wise Gardening in Central Oregon, at extension.oregonstate.edu/deschutes for suggestions.