Preserving Fall Leaf Colors

Preserving Fall Leaf Colors

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent

If only we could capture the beauty of autumn and hold it to our hearts all winter long! One of the spectacular features of fall is the wonderful coloring of tree leaves.  The more curious among us might wonder just how does fall color develop in trees?  It's a story that's been told before, but here it is one more time.

The purpose of plant leaves is to harness the sun's energy to feed the tree. It does this by way of the chloroplasts in leaf cells.  The chloropalsts contain the green plant pigment, chlorophyll.  This pigment enables the leaves to capture the sun's energy to make sugars and oxygen from carbon dioxide and water.  During the growing season the chlorophyll in present in abundant quantities.  As the weather turns cool the fall and the days shorten, the leaves stop producing chlorophyll.  

Some tree and shrub species are genetically capable of taking the carbohydrates left in the leaves and making them into anthocyanins.  These are the red pigments responsible for the reds, pinks, and purples in leaves.  As the chlorophyll begins to break down, the newly formed anthocyanins become apparent.  

Other plants are not genetically capable of making the anthocyanins.  When the chlorophyll breaks down in these plants, the leaves reveal the more stable orange and yellow pigments (carotene and xanthophyll).  

Brilliant oranges come from a mix of anthocyanins along with the carotenes and xanthophylls.  Trees that don't "perform" with remarkable colors lose all their pigmentation at one time and usually over a short span.

What are the weather conditions that favor the best fall color?  Autumn weather that favors good production of soluble carbohydrates in the leaves will lead to more splendid fall coloring.  Dry, sunny, and cool conditions but not lots of heavy frost are best for bringing out the reds, oranges, and bright yellows. 

If plants that are supposed to show spectacular color, don't... then their location or general health may be the problem.  Sunlight is generally needed for development of fall color, especially the reds.  If a plant is shaded, development of fall color will be deficient.  If the plant is experiencing stress, such as drought stress, fall color may be lacking.  A plant that is not cued into the advent of fall because it's still growing vigorously due to heavy watering and fertilization late in the growing season, may also lack brilliant color.

Can you remember pressing brightly colored leaves between sheets of waxed paper to preserve their colors?  It's one of those experiences of life that no one should miss. Here's how you do it. Place autumn‑colored leaves between two layers of wax paper.  Cover with an old towel or cloth rag.  Press the fabric with a warm iron, sealing the wax paper together with the leaf in between.  Cut your leaves out, leaving a narrow margin of wax paper around the leaf edge.

Of course that's the old‑fashioned way of doing things.  You can preserve fall leaves in your microwave oven.  Choose fresh leaves with the brightest colors.  You don't want fallen leaves that have already started to dry. Take separate leaves or small twigs and place them in the oven on top of two pieces of paper toweling.  Cover them with one sheet of paper toweling.

Run the oven for 30 to 180 seconds.  The drier the leaves, the less time they will need.  Observe caution, as you could start a fire in your microwave if they "cook" too long.  Be attentive.  Leaves that curl after removal, have not been dried enough.  Leaves that scorch, have obviously been left in too long.  Let the leaves dry for a day or two and then finish the leaves with a sealant, such as an acrylic craft spray.

You may get even better results if you use the microwave and silica gel for drying.  Place a 1.25 inch layer of floral silica gel in the bottom of a cardboard box.  Place the leaves lying flat.  Leaves should not touch and should be at least 1.25 inches away from the sides of the box.  Cover the leaves with a 1.25-inch layer of gel.  Place the uncovered box in the microwave.  You want the microwave to operate at about 200 to 300 watts so if your microwave has 2‑10 settings operate it at level 4.  If the oven only has three to four settings, it should be set at half.  If your oven has a high to defrost options, set the microwave on defrost.  Estimated drying time is 2.5 minutes if you're using a half pound of gel and about 5 minutes if using two pounds of gel.

Yet another way to preserve the leaves is to submerge them in a solution of glycerin and water. Use a mixture of one part glycerin to two parts water.  Place the mixture in a flat pan, and totally submerge the leaves (in a single layer) in the liquid.  You'll have to weight them down to keep them submerged.  In about two to six days they should have absorbed the liquid and be soft and pliable.  Remove them from the pan and wipe off all the liquid with a soft cloth.  Done correctly, the leaves will remain soft and pliable indefinitely.

So take some time with the children in your life and go out and collect some of the treasures of fall.  It's something they'll remember for the rest of their life...  I know I have.

Tree Care Fact or Fiction

Tree Care Fact or Fiction

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

Fact or Fiction? Newly planted trees should be firmly staked to keep them from falling over in the wind. 

Fiction... for most trees planted by home gardeners.  Trees that were growing in containers or were dug with an adequate size root ball don’t need staking... unless they’re being planted on steep slopes or in windy areas.  However, bare root trees frequently require staking while the roots are becoming established. 

If a tree must be staked for stability, it should be done the right way.  When trees are staked correctly, the staking allows for a swaying movement of the trunk all the way down to the ground.  Improper staking leads to taller trees with thinner trunks, less taper to the trunk, and a smaller root system.  Bad staking can cause physical injury to the bark.  Trees that have been poorly staked with the staking supports left on too long are more likely to break over in the wind after the stakes are removed.

The correct way to stake a tree is to place the stakes as low as possible on the trunk and no higher than 2/3 the height of the tree.  Use flexible materials to tie the tree to the stake. Do not use wire! Insure that the trunk can move back and forth all the way to the ground.  Staking should never be left on any longer than needed.  It should be removed when the tree roots have grown and become established, never leaving it on more than one growing season.

Fact or Fiction?  When pruning large limbs off a tree, it’s important to cover the wound left on the tree with pruning paint or a wound dressing.

Fiction.  Pruning paint can actually deter a tree wound from healing.  It’s preferable for the wound made by the pruning cut to dry out, allowing the cambium at the edge of the wound to produce callus tissue and eventually close over the wound.  Pruning paint or wound dressing has been found to slow or inhibit the process.

Fact or Fiction?  Wounds made to the base of trees by mowers or weed eaters can lead to the death of the tree.

Fact. Damage caused to the base of trees by careless mower operators or weed trimmers is a serious problem that often leads to the death of a tree. The problem isn’t usually caused by a small, one time “oops” wound.  Major wounds that damage more than 50 per cent of the circumference of the tree seriously injure and weaken it, but it’s the repeated small wounds that can be the most deadly.  If these repeated injuries end up “girdling” or encircling the tree at the same point on the trunk, the tree will die. 

You often see problems with “mower blight” or “weed trimmer blight” in commercial landscapes and parks where grass is allowed to grow up to the trunk of a tree.  Repeated hits over time lead to the swollen tissues around the base of the tree where it flares outward.  This swollen tissue is wound tissue that has formed from repeated wounding.  The trees may also be thinning or dying back from the top down as a result of the injury and girdling.

To avoid problems from“mower blight” or “weed trimmer blight”, mulch trees with bark or wood chips. The mulch helps control weeds, decreasing competition for water and nutrients, as well as decreasing the potential of mower or trimmer damage.  Research has shown that wood chip mulch can almost double plant growth the first few years after a tree is planted.  Use coarse textured organic mulches applied in a two to four-inch layer around the base of the tree, preferably the diameter of the planting hole or greater.

However, a layer of mulch greater than four inches deep or mulch placed directly next to the trunk can lead to problems.  Keep the mulch about four to six inches away from base of the trunk and don’t let the mulch become any deeper than four inches.

Fact or Fiction?  You can kill a tree by covering over troublesome tree roots that have “popped up” in the lawn with a layer of topsoil, even if the soil is only a few inches deep.

Fact.  Even a few inches of soil applied over tree roots can lead to serious problems and the gradual death of a tree.  This additional soil reduces the amount of oxygen reaching the roots and essentially suffocates the tree.  The amount of damage caused by filling in over tree roots varies with the type of tree, its age, and its health.  The scope of the damage also varies with the amount and type of fill.  Damage is not immediately evident.  It may only show up months or even several years after filling.

Fact or Fiction ?: The best time for planting a tree is in early spring before it leafs out. 

Fact... and fiction.  Horticulturists seem to disagree about the ideal time for planting trees.  Their recommendations vary from region to region.  The reason for this apparent disagreement seems to stem from regional differences in climate and available soil moisture. 

In some regions of the country, such as Western Washington, natural precipitation and subsequent soil moisture is most plentiful during the late fall and winter.  Because of more moderate conditions during the winter and plentiful soil moisture, root growth is possible ...making fall planting ideal on the west side of the mountains.  In the northeastern part of the country, soils during the winter are cold and root growth is minimal. Early spring planting, once the soil thaws, is best in these areas.

In our region it’s difficult for me to say with certainty whether spring or fall is the best time for planting, but I lean towards fall for planting.  However, trees and shrubs planted in the fall must be provided with adequate soil moisture, especially during mild fall and winter months.  A close second-best time to plant trees and shrubs is in the very early spring. The soil must also be kept moist to provide for root growth.  That’s the problem with fall planting and early spring planting in our region.  The best time for planting seems to be when many gardeners don’t have irrigation water available.  The solution is to water the trees with a hose.  Don’t wait until irrigation water is available.

If at all possible, trees should not be planted in late spring right after the tree has leafed out or during the heat of summer.  “Balled and burlapped” trees (trees dug out of the ground and their root balls are wrapped in burlap) lose 90 to 95 per cent of their roots in the digging process.  That’s a lot of root system that must recover before the high water demands of summer. New tree growth, hot summer temperatures, sunlight, and wind all create higher water demands on the tree.  Trees transplanted too late in the spring or in the summer are not able to reestablish their root systems quickly enough.  The result is drought stressed trees that may not survive.

Plants with Fall Color

The Leaves of Fall

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

Falling Leaves

Trees, shrubs, and vines are also amazing in the fall.  They take cues that winter is on its way from the cooling temperatures and shortening days.  Nature has programmed them to avoid cold weather by stopping growth and becoming dormant.  This is a physiological process triggered by hormonal changes in the plant.  Photosynthesis (the production of carbohydrates using the sunlight for energy) stops.  Nutrients from the leaves are moved to the twigs, buds, stems, and roots. 

Eventually, at the base of the leaf stem a layer of cells forms, stopping all movement of water and nutrients in and out of the leaf.  This layer is called the abscission layer and it’s at this point where the leaves break off and fall from the tree.

Unseen are the internal changes in the buds, stems, and roots, which are becoming less susceptible to damage from freezing temperatures.   Sugars increase to lower the freezing point of cell contents and the cell walls become stronger, along with other protective changes.  During the fall as temperatures continue to decline, plants become “acclimated” to cold temperatures until they achieve their maximum winter hardiness in mid-winter. A plant’s maximum potential hardiness is dictated by its genes. In the spring, a tree or shrub will start to de-acclimate and break its dormancy in response to warming temperatures and longer day length.

It’s interesting to note that many trees and shrubs also have a chilling requirement, much like the bulbs.  They will not readily break their dormancy and resume their growth in the spring unless they’re exposed to enough chilling temperatures.  A good example of this is peaches.  Peach trees need from 700 to 1000 hours of temperatures between 32 degrees and 45 degrees.  That’s why it’s hard to grow peaches in very warm climates, because they don’t get enough winter chilling to break dormancy. 

Gardeners may have noticed certain varieties of peaches advertised by mail-order nurseries as “low-chill” varieties.  These require less chilling than the standard varieties used in cooler areas of the country. What happens if there isn’t enough of a winter chill to meet the tree’s requirement?   Leaf development will be delayed and flower structure will be defective, resulting in poor fruit set.

Fall Color

Fall color is another amazing facet of nature that accompanies the onset of the dormancy process.  I grew up in upstate New York and have always been intrigued with the colors of autumn leaves.  I’ve told the story before of why leaves turn such beautiful colors, but it’s worth repeating again.  As the weather turns cool and the abscission layer starts to form, the leaves stop producing chlorophyll and the green color of the leaves disappears.  This reveals the more stable orange and yellow pigments (carotene and xanthophyll).

Some trees and shrubs also exhibit wonderful red colors.  These species are genetically capable of taking the carbohydrates left in the leaves and converting them to anthocyanins. Anthocyanins are red pigments responsible for the reds, pinks, and purples seen in autumn leaves. As the chlorophyll begins to break down, the newly formed anthocyanins become apparent. Brilliant oranges come from a mix of red pigments along with the orange and yellow pigments. Of course there are trees that aren’t very spectacular and lose all their pigmentation at once, turning from green to brown over a short span.

Autumn weather that favors good production of sugars in the leaves will lead to more splendid fall coloring. Dry, sunny, and cool fall weather, but not lots of heavy frost, are best for bringing out the vibrant reds, smashing oranges, and brilliant yellows.

Plants with Fall Color

Trees and shrubs that commonly provide our landscapes with fall color include red maple, Amur maple, Autumn ashes, red oaks, flowering pear, blueberry, sumac, sweetgum, dogwood, burning bush euonymus, Persian parrotia, and viburnums. Bright yellows come from birch, aspen, and gingko.  They are glorious!

A lack of fall color in a species or cultivar that is supposed to provide a good display can be attributed to its location, growing conditions, or general health.  Full sunlight is needed for the best development of fall color, especially the reds. A plants that’s shaded, will probably not develop good fall color. Plants experiencing drought stress or other problems may also be color deficient in the autumn.  An extremely vigorous plant that’s still actively growing in the fall due to late season pruning, fertilization, or excessive watering will also fail to color up nicely.  This is also a clue that the plant is not becoming dormant and acclimated to cold temperatures.  These plants are more likely to sustain winter injury due to freezing temperatures, especially severe cold early in the winter.

Why Leaves Turn Color in the Fall

Why Leaves Turn Color in the Fall

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent

Tree leaves contain different types of pigments.  The predominant one is usually green and it comes from the chlorophyll needed for photosynthesis... the process by which the leaf captures sunlight and uses that energy to make sugars out of water and carbon dioxide.  In the fall as the leaf begins the process of senescence or dying and falling off the tree, photosynthesis stops and chlorophyll breaks down, revealing the underlying yellow and orange pigments in the leaf...these are carotene (orange-yellow pigment), and xanthophyll (yellow). Red and purple colors come from anthocyanin pigments. Anthocyanins are not masked but actually start to build up in the leaves of certain trees as the chlorophyll breaks down.

The weather that leads to the best fall colors are those which promote the highest levels of sugars in the leaves.  Bright, sunny warm days and cool nights will lead to the most brilliant hues of oranges through reds and purples. Heavy frosts and overcast days can diminish fall color, while a mild drought can favor anthocyanin production and fall red color.&

Its important to point out that some trees such as red maple, dogwood, sweetgum, and dogwood are capable of exhibiting fall color under the right conditions and other plants, such as sycamore, black locust, black walnut, linden, catalpa, and elm will never provide an attractive autumnal display.

Conifers are cone bearing trees. Most conifers are needled evergreens. While most conifers don’t lose their leaves in the fall, they do lose some of their oldest needles each year. This is usually a gradual, unnoticed process, but in some years needles may turn bright yellow in the fall and drop over a short period of time. There are a few deciduous conifers, such as larch and dawn redwood, which lose all their needles each fall.