Tag Archives: trees

The Mysteries of Fall Color

In case you were wondering…
Every autumn in Illinois brings with it a breathtaking change of color in the leaves of our trees, but although it’s late September, temperatures have been steadily topping out in the nineties every day.  Not a traditional sign of Fall, yet the trees are changing color and dropping leaves as if they were not aware of the hot and humid weather.
Aren’t the leaves supposed to change when it gets cooler and we see some frosts overnight?
Do the trees know what time of year it is despite the unusually warm temperatures?
One explanation, according to Native American myth, is that the hunters in the Heavens killed the Great Bear in autumn and its blood dripped over Earth’s forests coloring some of the leaves red.  As the hunters cooked the meat, fat dripped from the Heavens and colored some of the leaves yellow.
Not scientific enough for you? Need a more botanical answer?
In case you were wondering what actually initiates the changing color of the leaves and their eventual fall to the ground, read on…
Most people think that cool weather or frost causes the leaves to change color. It is true that there is usually a correlation between the cooler air and the onset of the autumn show.  However, while temperature may impact the color intensity, it has less impact on the timing of the color transitions we see in the Fall than do other factors.
A quick trip back to high school Botany 101.  During the spring and summer most of the foods necessary for the tree’s growth are manufactured in the leaves.  This food-making process takes place in the numerous cells containing chlorophyll, which gives the leaf its green color. This extraordinary chemical absorbs the energy from sunlight that is used in photosynthesis, the transformation of carbon dioxide and water to carbohydrates, such as sugars and starch.
In late summer or early autumn, the days begin to get shorter, and consequently, the nights are longer. Like most plants, deciduous trees and shrubs are rather sensitive to the length of the dark period each 24-hour cycle. When nights get long enough, the cells of the leaves begin to block transport of materials such as carbohydrates from the leaf to the branch. They also block the flow of minerals from the roots into the leaves. Because the starting time of the whole process is dependent on night length, fall colors appear at about the same time each year in a given location, whether temperatures are cooler or warmer than normal.
The fact is, the vivid yellow and orange colors have actually been there throughout the spring and summer, but we haven’t been able to see them. The deep green color of the chlorophyll, which helps plants absorb life-giving sunlight, hides the other colors.  In the fall, fewer hours and less intense daylight prompt the leaves to stop the food-making process. The chlorophyll breaks down, the green color disappears, and the yellow and orange colors already in the leaf become visible again to the human eye.  As the trees break down the green pigments and nutrients stored in the leaves they are shuttled into the roots for reuse in the spring.
Along with the green pigment of chlorophyll are carotenoids, yellow to orange pigments, which, for example, give the orange color to a carrot. At the same time other chemical changes may occur which produce red anthocyanin pigments resulting in even more variation in the Fall color scheme.  Some mixtures give rise to the reddish and purplish fall colors of trees such as dogwoods and sumacs, while others give the sugar maple its brilliant orange. For most of the growing season these colors are masked by the great amounts of green coloring.
The variations in Fall color are due to the mixing of varying amounts of chlorophyll residue and the other pigments in the leaf combined with a varied response to weather conditions. For instance, as the nights become cooler, the sugars trapped in the leaves of some oaks and maples will often form a red pigment.  The degree of color will also vary from tree to tree.  Leaves directly exposed to the sun may turn red, while those on the shady side of the same tree or other trees may be yellow.
As the fall colors appear, other changes are taking place. At the point where the stem of the leaf is attached to the tree, a special layer of cells develops and gradually severs the tissues that support the leaf. At the same time, the tree seals the cut, so that when the leaf is finally blown off by the wind or falls from its own weight, it leaves behind a leaf scar. Most of the broad-leaved trees in Illinois shed their leaves in the fall. However, the dead brown leaves of the oaks and a few other species may stay on the tree until growth starts again in the spring.
In general, autumn weather conditions favoring the most brilliant colors are warm sunny days and cool, but not freezing, nights. When there is mainly warm, cloudy and rainy weather in the fall, the leaves may have less red coloration.  A few hard frosts can cause the leaves to wither more quickly and drop to the ground.
So, in case you were wondering, with all due respect to the Native American myths, it is a combination of temperature, light, and water supply that have an influence on the onset, the degree, and the duration of fall color.
Enjoy it while you can, because it doesn’t last long!

Benefits of Fall Planting

Most of us love fall, but plants love it even MORE!
 

Most people think of fall as the end of the growing season and the beginning glimpse of another Chicago winter.  Well try to look at it as an ideal time to plant!

Fall is a perfect time for planting shrubs, trees, grass seed, and even perennials if they have a developed root system. Fall planting gives plants time to develop roots before winter’s blustery conditions.  The conditions are also less stressful and there may be more reliable precipitation.

What happens during fall conditions is a plant’s leaf and flower production is usually slowing down and approaching dormancy. Therefore, a plant can focus on root production.  Roots continue to grow when other parts of the plant are not. Generally speaking, root systems will keep growing as long as the soil temperature is at least 50 degrees.

Although we generally get more rain in fall, the good news is that plants use less water then.  Because days are increasingly shorter and cooler in the fall, plants are going to be photosynthesizing less and using less water.

Fall is also when depleted nurseries can begin to dig plants again, so varieties that were either unavailable or just downright unsightly in July and August, may become available.

Finally, don’t forget about BULBS!  Its often surprising why more people don’t take advantage of this relatively inexpensive way to welcome in Spring.  To achieve a gorgeous Spring show bulbs are planted in late fall.

Spring Tulips

If you’d like to start planning a fall project, it is right around the corner, so call us now and we will be happy to assist you!

Favorite Plant Series: Taxodium distichum

One of my favorite trees is Taxodium distichum, or Baldcypress (also Bald Cypress). Once you recognize it, it’s always a delight to see. Baldcypress has the rare distinction of being a stand-out tree in virtually any type of setting or application. Alone or in groups, in formal or naturalistic settings, urban or wild, Baldcypress often becomes the focal point of a well-thought-out planting design. Part of that distinction arises from the fact that it has yet to have been overplanted – at least in Chicagoland-area landscapes – and is often greeted with delightful curiosity by the uninitiated.

While such a versatile tree, there are limitations to Baldcypress’s use given its eventual size and habit. Growing 50’-70’ by 20’-30’ wide, Baldcypress takes on a mostly pyramidal shape. While tall, it may not perform as a traditional shade/canopy tree for many years, if at all. Although the northernmost portion of Baldcypress’s native range is technically southern Illinois, the tree does quite well in northern Illinois and southern Wisconsin. Baldcypress does well in wet, dry, and well-drained soil conditions and is relatively salt-tolerant.

Leaves in springtime are a bright yellow-green and eventually turn a medium sage green come summer. The leaves turn orange-brown in autumn and hold for a while before dropping as winter approaches. Interestingly, Baldcypress (along with its cousin Dawn Redwood, also hardy in this area) is one of only a few varieties of cone-bearing trees that lose its leaves in the winter. Seeing the small ½” – 1” cones Baldcypress produces adds to the surprising nature of the tree. The reddish-brown bark with a fibrous nature can be striking in winter.

Famed modernist landscape architects such as Dan Kiley and Peter Walker used Baldcypress in formal, urban settings (see Fountain Place in Dallas and water features outside UBS Tower in Chicago – see picture). Locally, the Heritage Garden at the Chicago Botanic Garden features a pruned baldcypress hedge, now several decades old. Such formal cues can be also adapted to residential settings, as well as using Baldcypress as a standalone specimen tree or loose grouping. With such versatility, Baldcypress might be the “problem solving” tree for your landscape.

Taxodium form

baldcypress_chicago

Bald cypress in the landscape

Up close of the leaf

Written by Ken Horinko, ASLA
Landscape Architect

Why Leaves Change Color

fall maple

During the growing season, chlorophyll, essential for photosynthesis, is continually being produced and broken down and leaves appear green. As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids (responsible for orange, yellows and browns in things like bananas and clementines) and anthocyanins (responsible for reds and purples in items like cherries and berries) that are present in the leaf are then unmasked and show their colors.

Both chlorophyll and carotenoids are present in the chloroplasts of leaf cells throughout the growing season. Most anthocyanins are produced in the autumn, in response to bright light and excess plant sugars within leaf cells.

A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays. During these days, lots of sugars are produced in the leaf but the cool nights and the gradual closing of veins going into the leaf prevent these sugars from moving out. These conditions-lots of sugar and lots of light-spur production of the brilliant anthocyanin pigments, which tint reds, purples, and crimson. Because carotenoids are always present in leaves, the yellow and gold colors remain fairly constant from year to year.

The amount of moisture in the soil also affects autumn colors. A late spring, or a severe summer drought, can delay the onset of fall color by a few weeks. A warm period during fall will also lower the intensity of autumn colors. A warm wet spring, favorable summer weather, and warm sunny fall days with cool nights should produce the most brilliant autumn colors.

Some of my favorite places to enjoy the onslaught of fall color?  Visit now and often over the next few weeks and watch the marvelous display.

Independence Grove (shown in photo above)

The Morton Arboretum 

 

Watering Guidelines – new trees and shrubs

During the spring we generally receive a sufficient amount of moisture.  Spring to summer is probably the most critical transitional period because moisture levels can drop quickly and soil moisture availability rapidly declines.  This situation can be exacerbated by overly hot and windy conditions.

When plants start to show signs of stress by wilting permanent damage to the vascular system may have already occurred.  Prevention is the key; therefore we have prepared the following guidelines on the basics of proper watering procedures.

Time of Day to Water

The BEST time to water is about 3 a.m. to 10 a.m.  At this time the air is cool and very little evaporation loss occurs before the water reaches the ground.  When the sun rises and the air warms, the liquid quickly evaporates from the leaves.  Watering early in the evening encourages fungal infection (fungal infections thrive in cool wet conditions); watering in the heat of day is bad because much of the water evaporates before reaching the ground.  This accelerates buildup of soluble minerals in the soil that over along time can be ruinous to soil health.

Accurate Measuring

When you water, water deeply.  This means water for a long time, allowing the water to soak into the ground.  Ideally, you should provide one inch of water with every soaking, but not more than once per week.

Remember to take rainfall into consideration when monitoring your watering. Use a rain gauge to monitor the amount of water your landscape receives from rainfall and your irrigation system (if applicable).

Be careful…you can over water your plants!  Roots need both water and oxygen to thrive.  Over watering can kill plants because constant moisture suffocates the roots, thereby causing them to die and rot.  Inspect the area BEFORE watering by tunneling with a deep root feeder or stake.  If the soil is dry on top, it might still be moist underground and not need water.

Newly Planted Trees

When watering newly planted trees, remove the nozzle from your hose, wrap the hose in an old bath towel  (so it will disperse the energy of the spray) and set the hose at the base of the tree.  Water the area at a low pressure every other day (45 to 60 minutes) for 3 to 4 weeks, based on your soil conditions.  Make certain to change the position of the hose to water evenly.

Newly Planted Shrubs

Shrubs can be watered similarly to trees except the time frame drops to 10 to 15 minutes each.  Avoid watering foliage, most plants DO NOT like being watered from above because moisture build up on leaves encourages fungal problems.

For more information there is a great article by the University of Illinois Extension.