Why Do Leaves Change Color In The Fall?

leaves changing color

What time of the year do you like the most? Is it the winter when everything is covered with a blanket of white? Is it the spring when many trees and shrubs show off their beautiful flowers? Is it summer when lawns are green and flowers are blooming everywhere? Or, is it fall when the air turns cooler and the leaves on the trees take on their fall colors in shades of yellow, red, orange and brown?

All seasons have their pluses and minuses, but fall is a very colorful time as the trees and shrubs change from different shades of green to various hues of yellow, red, orange and even brown. It is first important to understand why leaves fall off.  All deciduous plants, or plants that lose leaves in the fall have a layer of cells that comprise the abscission layer.

As these cells begin to breakdown at the end of the growing season, the leaf will eventually break off and fall away. How long the color lasts mainly depends on how long it takes for the abscission cells to breakdown and fall away. The longer the process takes, the longer the colors lasts.

How do leaves change color?

The process starts when sunlight time shortens and air temperatures cool down. Less daylight and cooler nights work together to produce more pigments in the leaves. Chemicals and nutrients start moving out of the leaf and into the stem of the leaf. Trees and shrubs use different processes to break down the sugars produced in the leaves into carbohydrates and other foods that lead to the change of leaf color.

Yellow color occurs during this breakdown period. As the production of chlorophyll in leaves stop, two pigments, carotin and xanthophyll, which produces the yellow color, become visible. The pigments are always there, but are masked by the green color of the chlorophyll.

Red colors depend on bright days and cool nights to become visible. Bright light increases sugar production within the leaf, but the cooler nights prevents the sugars from leaving the leaf.  When sugar content increases within the leaves, a red pigment, anthocyanin, is produced. Orange is the color that comes from mixing red and yellow together.

Weather plays a role in Fall Color

Depending on the amount of red or yellow pigments produced in the leaves determines the shade of orange the leaf becomes. If the nights get too cool or the days are overcast, you end up with an “off year” for tree color. And a killing frost ends the show completely by killing all the pigments in the leaves no matter what stage they’re in.

The intensity of the colors, especially scarlets, oranges and golds, the weather must be almost perfect along with plenty of soil moisture.  The sooner a hard frost occurs, more leaves are killed off before having the opportunity to change color. The color that the leaves turn in the fall depends on the plant’s genetic makeup.  If it is important to you to have plants with a nice fall color, inquire about the plants fall color before purchasing.

Trees are a great source of leaf mulch.  Instead of raking your leaves, grid them up with your mower and recycle the nutrients back on to your lawn.  Leaves do not significantly add to the thatch layer. When leaves start turning color is also a great time to root feed the trees and shrubs in your yard and landscape.  Contact your local Spring-Green to add this important service.  Your landscape will appreciate it.

Why Did They Fertilize Over The Top of All The Leaves?

leaves on your lawn after you fertlize

This is the time of year when leaves come raining down from all the deciduous trees and shrubs, since it is the end of the growing cycle for most of these plants. As days get shorter and shorter in the fall, it triggers a reaction in the plant that it is time for the leaves to stop taking in nutrients, change color and then drop to allow new buds to develop for the next year.

If you search the term, “rake or not to rake” you will find dozens of sites that discuss the advantages of mulching your leaves. Although, most rake them up, filling expensive yard waste bags, and lug them to the curb so that they can be picked-up by the trash company.

In the city where I live, the bags are relatively cheap, but each bag needs a sticker that costs about $3.00 per bag. I have seen 30 or 40 bags in front of some people’s lawns and, at $3.00 per bag, it can get really expensive quickly.

leaves on your lawn

Should I grind up my leaves before I fertilize?

Of course, the better thing to do is to just run your mower across the lawn to grind up the leaves into small pieces less than the size of a dime. As long as there is about a half of an inch of grass showing through the leaves, your lawn will do all the work for you.

Earthworms will feed on the leaves and the microbes in the soil will feast on the leafy dinner.  Depending on the amount of leaves that fall, you may have to double-cut the lawn or use a rake or leaf blower to spread the leaves across the lawn to eliminate any large piles.

One thing that will definitely help with the decomposition process is fertilizer, more specifically: nitrogen. Microbes do a better job of composting when they have nitrogen as food and will work faster composting the leaves. Your lawn will grow better and develop a healthier plant when the leaves are composted. It does not really matter if the lawn is fertilized before or after the lawn has been mowed. 

If the fertilizer is applied as a granule, the leaves are relatively dry and the grass blades can still be seen through the leaf cover, the fertilizer will easily filter through the leaf cover. The same is true when applying a liquid application, although the liquid material will not filter through the leaves. As long as the leaves are mulched, though, the fertilizer will be used by the microbes even though the nitrogen is on the fallen leaves and not as much on the grass blades.

Mulching your leaves is a much better way of removing them. Do your lawn a favor this fall and give it plenty of food so that your lawn will be greener and healthier in the spring.

If you have questions about fertilizing over the leaves on your lawn, contact your neighborhood lawn care professional at Spring-Green.

Fall Webworms: Have You Seen Webs In Your Trees?

little girl jumping into a pile of leaves

During a recent trip to meet with our Franchise Owner in Springfield, MO, I got to witness an amazing amount of damage from Fall Webworms. This caterpillar is a gregarious feeder on the leaves of over 100 tree species, but it prefers mulberry, oak, hickory, walnut among many others.

fall webworms showing up in your trees

As many people are familiar with the Eastern Tent Caterpillar that feeds on the leaves of crabapples and other fruit trees. Both of these, Fall Webworms and the Eastern Tent Caterpillars will create webs in trees.

The webs for Eastern Tent Caterpillars are created in the forks of branches whereas the Fall Webworms make their webs at the end of the branches. Also the Eastern Tent Caterpillars leave their nests to feed on leaves whereas the Fall Webworms remain within their webbing.

tree with fall webworm making its web

The Fall Webworm constructs ever-increasing webs or ”nests” that can contain several hundred caterpillars. Once they finish feeding on one branch, they move on to the next branch. The nests can become as large as two or three feet across. They will fill with dried leaves, cast skins and excrement. They will display a defensive movement where they all raise themselves at the same time in an effort to frighten off a predator, such as a bird.

Although the damage may look severe, rarely will feeding cause any major problem with the tree. By the time September rolls around, the tree has produced enough carbohydrates for the year. Plus, as the weeks go on, the leaves will start to drop with the onset of fall.

As the caterpillars reach maturity, they will move down the tree and find a protective place to pupate, usually under fallen leaves or other protected areas. The adults will emerge the next year and the female will lay her eggs on the underside of leaves.  In late summer, the eggs will start to hatch and the whole process will start again.

As we drove around Springfield, we saw nests at the top of trees that were 60 feet high and we saw entire small trees covered with webs. Smaller trees can be treated with a number of insect control products, but many people choose not to worry about the nests. For the most part, the webs will be destroyed by normal wind, rain and snow. In some cases, the webs may remain until spring.

tree full of fall webworm webs

When asked by a customer what could be done to treat the tree, the Franchise’s Team Member suggested that the customer place a decorated pumpkin under the tree and call it her Halloween Tree. It does look like it is covered by spider webs and looks very creepy. The customer liked the idea and plans to make it a Halloween tree.  Lemonade out of lemons.

For more information about tree care contact your local Spring-Green.

Have You Seen Weird Growths On The Leaves Of Your Trees?

house with trees

At this time of year, I receive pictures from Spring-Green employees of weird growths on leaves that are causing concern from their customers. Often times, the leaves have fallen to the ground and covered with weirdly-shaped structures growing out of the leaf surface. These are galls. Galls are abnormal growths caused by various organisms, such as insects, mites, nematodes, fungi, bacteria and viruses.

leaf gulls

Galls can take on an assortment of shapes and colors, which is why customers become concerned. Fortunately, these galls rarely threaten the health of the plant.  The reason why leaves often fall when there are numerous galls present is due to the sheer weight that is added to the leaf. The problem is purely cosmetic and control is normally not required or recommended.

An assortment of insects and insect relatives are the source for many of these galls. These organisms may often secrete a substance in the leaf, which reacts by increasing its normal plant growth hormones. This results in an increase in the size or number of cells, which is what causes the gall.

Most of the gall production occurs in the spring when leaves are first beginning to open. The organisms that form the gall often live within the gall itself as it develops around them.

leaf gulls

One type of organism is called eriophyid mites.  Different species of these mites can form spindle galls, bladder galls or velvet galls. Psyllids will form nipple galls or blister galls. Nipple galls form on the underside of the leaf surface.  Aphids will cause a gall to develop on the stem or petiole of cottonwood or poplar trees. Adelgids are the source of galls on many conifers, including the Cooley Spruce Adelgid gall.

There are even tiny species of wasps that cause galls to develop on the leaves of some trees.  One of the more interesting is the Jumping Oak Gall. These galls are formed by a sting-less wasp and effects White Oaks. The female lays a single egg in the developing leaf bud. When the egg hatches, the larva lives in and feeds on the gall tissue that forms around it. In the early summer, the galls will fall to the ground and the larva will jump in an effort to escape the gall, similar to the jumping of a Mexican Jumping Bean.

Galls are just part of nature and their formation usually does not affect the overall health of the tree or shrub. They may cause some leaves to fall, but they are going to fall anyway, so don’t let them bother you.