Redbud leaves turning yellow

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Friday – July 13, 2012

From: Denton, TX
Region: Southwest
Topic: Diseases and Disorders, Watering, Trees
Title: Redbud leaves turning yellow in mid-summer
Answered by: Guy Thompson

QUESTION:

The leaves on our redbud trees are turning yellow. The yellow leaves are pale with no other spots and no dark veins. I don’t know for sure which variety of redbud they are or how old they are (more than 10 years old). The heat and drought of 2011 hit us pretty hard. Is this a result of last year’s drought, or is there something else going on? What can we do to save them? Thank you!

ANSWER:

Redbuds and many other trees normally drop some leaves early when drought-stressed. This is an adaptation to reduce the need to take up moisture from the dry soil. Don’t worry too much if the branches are still alive (scrape off the bark on a defoliated twig to see if it has green and moist tissue) and if 50 % of the leaves remain green. New leaves will appear next spring.

If a great number of leaves are turning yellow, the trees may still be drought-stressed. Drought stress can show up even a year or two after a drought because part of the root system has not yet recovered. If that is the case, you should make sure that the soil around the trees remains moist. Deep watering throughout the root zone (out to the drip line) once a week will assure that the trees are not short of water. Mulching the area under the trees will help conserve soil moisture.

Plant nurseries around the country sell several varieties of redbud. Cercis canadensis var. texensis (Texas redbud) is more drought-resistant than Cercis canadensis (Eastern redbud) and less drought-resistant than Cercis canadensis var. mexicana (Mexican redbud). The seed pods of Texas redbud tend to be reddish in color while the Eastern redbud seed pods remain green. That may help you identify yours.

Drought stress would make the trees more susceptible to disease. It is possible that you trees are not drought-stressed but suffering from verticillium wilt. Here is a on this subject.

Good luck in keeping these attractive trees alive!

From the Image Gallery

Texas redbud
Cercis canadensis var. texensis
Eastern redbud
Cercis canadensis
Mexican redbud
Cercis canadensis var. mexicana

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Yellowing redbud tree may be getting too much sun

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Q. My mature redbud tree had leaves turning yellow in July and falling in August. – G.D., Springfield

Answer by Master Gardener Mark Bernskoetter

Redbuds are an “understory tree,” which means they prefer to grow in the shade of another tree because they cannot tolerate our hot summer sun. If the tree is getting more sun now than in the past years (because of growth or changes to a nearby tree or structure), the leaves may be getting sunburned.

Another concern is when soil becomes compacted, especially if you have vehicles parking under it or lots of foot traffic. Try core aerating your ground around the tree and several feet out beyond the drip line, and then cover the area with an inch or so of compost. This combination can help the organic matter get into the soil and create a more loose structure for roots to grow.
Drought will also affect the tree. Redbuds prefer their soil to be more on the moist side. If it gets especially dry, remember to water the tree.
The good news is your redbud will probably survive, but without help, it will likely die earlier than the average lifespan of a redbud, which is about 60 years.

Q: I have an old grapevine growing along my fence. How far can I trim back the vine and not damage it? – B.W., Ash Grove

Answered by Master Gardener Mark Bernskoetter

Ideally, any woody plant should not be pruned back more than a third of the total growth in any year.

Early March is the perfect time of year to prune your grapevine; pruning at this time is called dormant pruning. The majority of the severe winter weather, which can be hard on plant tissue at a fresh pruning cut, is over by then, but budding and sap flow have usually not started yet.

Q. Last year, why did I have few berries on my holly? – S.R., Nixa

Answered by Master Gardener Mark Bernskoetter

Most hollies are dioecious, meaning the male flowers provide pollen to the female flowers (which then produce berries). Your holly is most likely either male or female. Only females produce the berries, and only after being pollinated from a male holly. The best pollinator for any holly is a male of the same species. However, one male plant can pollinate a few females.

If you have a bush that is producing berries, it is female. However, the male plant that usually fertilized it may have been removed by a neighbor, so there is no pollen for fertilization. It could also simply mean the male was not in bloom at the same time as yours last year.

Late spring frost may kill the flowers, whether pollinated or unpollinated. After a long winter and short spring, there can be fewer flowers, which results in fewer berries. During a drought, the berries may wrinkle and fall off the bush. Holly berries are often eaten by birds, but if they are not, and the berries remain on the plant too long, the bush will not put much energy into growing more flowers the next year.

Readers can pose questions or get more information by calling 417-874-2963 and talking to one of the trained volunteers staffing the Mas­ter Gardener Hotline at the University of Missouri Exten­sion Center in Greene County located inside the Botanical Center, 2400 S. Scenic Ave., Springfield, MO 65807.

Newly Planted Tree Leaves Turning Brown, Yellow or Wilting? Try…

Gently placed in its planting spot, sealed with soil and quenched with water–you can’t wait for your new tree to flourish!

But, after weeks of watching your tree soak in its brand-new life, you see… brown, yellow or wilted leaves?

When new trees have drooping or discolored leaves, there’s a problem. So, what can you do to help?

Why You’re Having Problems with Newly Planted Trees and What to Do

Adjusting to a new home is stressful for young trees. The sudden change in environment can lead to all sorts of problems, which is called transplant shock.

Transplant shock usually starts at the tree’s roots. Sometimes roots don’t have enough room to spread out or didn’t get enough water right after being planted. Whatever the case, trees wear their heart on their sleeve–or should we say their leaves. That’s why you see those wilted, yellow or brown leaves.

Is my newly planted tree dying?

You can often revive a shocked tree, but you’ll first need to make sure it’s alive and well.

  • Try bending a tree branch. If the tree’s dead, it will easily snap. Live tree twigs are nimble, so they’re flexible, bendable and much harder to break.
  • Or scratch a spot on the twig with your fingertip or a pocket knife. If the layer immediately under the bark is moist and bright green, the tree’s alive.

What to Do About Newly Planted Tree Leaves Wilting, Turning Yellow or Browning

Trees often suffer from transplant shock because their roots don’t have enough room to establish themselves.

Shocked trees also need a little TLC to get them back on track. Here are a few things you can try:

  • Give tree roots at least one inch of water per week.
  • Apply a two-to-four-inch deep layer of mulch from the base of the tree to the drip line. Keep mulch five inches away from the trunk.
  • Don’t over prune young trees, unless it’s to remove dead or damaged branches.

If those steps don’t appear to help your tree, consider replanting the tree in a larger hole. First, read this guide about transplanting trees. If you’re unsure if your tree needs moved, ask an arborist. Replanting your tree again could shock it once more.

TreeHelp Product Suggestions:
Use an Annual Care Kit to treat your redbud tree, an excellent annual maintenance practice.

Check for seed availability

Eastern redbud
G. Lumis
Leaf of eastern redbud
G. Lumis
Bark of eastern redbud
G. Lumis

Hardiness Zones: 4 to 9
Height: 30 ft
Spread: 25 ft
Form: rounded
Type: deciduous tree
Annual Growth Rate: 12 to 18 inches
Light: Full sun to shade
Moisture: Grows better in moist soil
Flowers: Purplish-pink
Fertilizer: TreeHelp Premium Fertilizer for Redbud

The Redbud tree is a relatively small tree with spreading branches and a small short trunk. The Redbud is a poplar ornamental tree, which can be found in many gardens and streetscapes. The tree is one of the earliest flowering trees and is often used to add color to gardens.

The purple pink flowers of the eastern redbud appear all over the tree in early spring. The flowers are even produced on large trunks. Redbud has a yellow fall color and is shade tolerant.

The Redbud grows throughout much of the eastern United States and extends as far west as Texas, Oklahoma and Kansas.

Cultivars
var. alba – The flowers are pure white.

‘Forest Pansy’ – The new leaves are scarlet becoming maroon as they mature. The flowers are pink. This cultivar may not be as hardy as the species.

‘Flame’ (‘Plena’) – Double pink flowers appear at the same time as the leaves. Seldom sets fruit.

‘Silver Cloud’ – The leaves are variegated with pink and white. The plants are 12 feet tall and wide.

Insects

Tree Hoppers

Treehoppers lay eggs under the bark of twigs. The insect itself is not seen but the white, sticky froth covering the eggs is quite noticeable (see image). The insect is seldom serious. Use Horticultural Oil in a dormant spray dosage to control treehoppers. The Horticultural Oil should be applied when the temperatures are between 35 and 85 degrees Fahrenheit.

Scale Insects

Scale insects are small, non-mobile insects that attach themselves to the wood and sometimes the foliage. Scale is most common on the new tender woody growth. When adult scale is attached to the tree, it often appears as crusty or waxy bumps on the tree and is often mistaken for part of the tree’s own growth, but it is actually an insect. The scale sucks sap from the tree and causes the leaves to turn yellow and drop. Often a sticky substance can be found near the scale or on the leaves. This is a secretion from the scale called honeydew and often acts as an attractant for ants or as a growing source for sooty mold.

In the spring or mid-summer, small, almost invisible nymphs emerge from under the female shells and move to infect new areas of the tree. This is the only time in the life cycle of scale that the insect moves.

To effectively control scale insects and limit damage, Horticultural Oil should be sprayed on the tree. The Horticultural oil serves to suffocate the scale and eggs. In the spring or early summer if the crawling nymphs are present, spray the trees with to prevent the new nymphs from further infecting the tree.

Spider Mites

Spider mites are an extremely tiny pest, and generally appear as a brown, red or purple specks on the underside of leaves. Mites infest leaves and cause the leaves to appear speckled with yellow spots or wilted and curled. A fine silken webbing can sometimes be seen on the underside of the leaves. Intense infestations during hot, dry weather can cause the leaves to curl and drop.

To confirm if the tree has a spider mite infestation take a close look at the undersides of the leaves for small insects, the size of ground pepper. You may need to use a small magnifying glass to adequately see the spider mites. Another way to examine for spider mites is to take a sheet of white paper, hold it under a group of leaves and give the leaves a few sharp taps to shake some of the spider mites loose. On the white paper the spider mites can be easily seen.

Spider mites damage the tree by sucking sap from the underside of the leaves. The bite marks appear as a yellow speckled pattern on the top and bottom of the leaf. As the season progresses and the temperature becomes hotter and dryer (above 70 degrees F.) the population of spider mites will increase exponentially and can rapidly defoliate a tree, especially if the tree is having trouble taking up water during drought periods. To control mites, spray the tree with Bug Buster. Be sure to spray the underside of the leaves as well as leaf crotches as this is where most spider mites and their eggs are found.

Diseases

Dieback/Canker

Dieback/Canker is the most destructive disease that attacks Redbud trees. It is first seen as a tree’s leaves wilt and turn brown. Often cankers can be seen on branches and twigs. The cankers can either be seen as visible cankers on the surface of the branches or as dark sunken areas with black centers.

The canker or dieback is caused by a fungus (Botryosphaeria ribis) which attacks not only the redbud but more than fifty other types of trees and shrubs. The disease is spread throughout the tree, or from tree to tree, by splashing rain and winds that move the fungus from diseased areas to healthy parts of the tree. The fungus then enters the tree through wounds or dying branches. The fungus gradually spreads out within the tree’s vascular system slowly blocking the tree’s vascular system and inhibiting its ability to transport nutrients and water. The result is a gradual dieback of branches as the flow of nutrients and water is cut off.

There is no effective chemical control for the canker. If canker is identified in a tree, prune out and destroy dead branches and infested areas. Be sure to make pruning cuts at least 3 or 4 inches below the canker, so that the cut is into healthy viable wood. After every pruning cut, be sure to properly sanitize the pruning tools so that the fungus is not transported on the tools and infects healthy parts of the tree.

An effective pruning and sanitization program can be helped with a fungicide spray program. Spray both the healthy and diseased sections of a tree with Liquid Copper during and shortly after periods of excessive rain. Using a fungicide such as Liquid Copper will not eliminate the disease but it can help slow the spread of the fungal disease to healthy trees.

Leaf Spots

Leaf spots can be a problem during wet weather. The spots appear as small brown or black spots on the top of leaves. Since the disease is rarely serious, no chemical controls are normally needed, however, in severe cases or to improve the look of the tree, spray the tree with Liquid Copper. The fungicide spray should be applied when the leaf spots are first noticed and again in about 14 to 20 days. The following spring, shortly after bud break, re-spray the tree with the Liquid Copper to ensure no over-wintering of the spot disease. Since the leaf spot fungus over winters in the fallen leaves and then re-infects the tree the following spring, it is important in the autumn to collect up and remove any leaves that have fallen to the ground.

Verticillium Wilt

Verticillium wilt attacks and kills redbud trees. Verticillium Wilt is a very common disease that attacks a large number of trees. It is caused by a soil-inhabiting fungus called Verticillium. The disease fungus can be spread by many methods including from plant-to-plant, through the soil, groundwater and often by infected pruning equipment that has not been properly sanitized. The disease normally enters the tree through the soil, but can also be introduced into a tree through a wound. Once in the tree, the fungus begins to spread throughout the tree’s vascular system, as the fungus level increases the tree’s vascular system becomes blocked preventing the tree from adequately moving water and nutrients throughout the tree.

The first signs that a tree has a Verticillium Wilt infection is the yellowing and then browning of leaves at the ends of some branches. Initially the yellowing and browning of the leaves is spotty throughout the tree and does not follow a uniform pattern. As the fungus begins to block the vascular system, the browning of leaves becomes more acute and more wide-spread. New leaves generally are either non-existent, undersized or yellowed.

As the disease spreads, the infected tree may slowly die, branch by branch over several seasons. The symptoms and severity of Verticillium wilt are much more harsh during droughts.

There is no chemical control for Verticillium Wilt however there are several steps that can be undertaken to help control the spread of the disease, as well as enhance a tree’s ability to control or even contain the disease. These include pruning, fertilizing and watering.

Prune and remove all dead wood. The pruning should be a few inches below the diseased area, so as to remove as much of the fungal concentrations as possible. When pruning do not remove branches that have recently wilted as they may reflush again in a few weeks or the following spring. When pruning be sure to properly sanitize the pruning tools after each cut.

Give the tree a very good fertilization with a slow release nitrogen. The TreeHelp Annual Care Kit contains an appropriate fertilizer for Redwood trees, as well as a Redwood mycorrhizal treatment and biostimulant to assist the tree in taking up and metabolizing moisture and nutrients.

It is important to give a Redbud tree suffering from verticillium wilt a deep root watering at least twice or three times a week. The objective of a deep root watering is to ensure that the water penetrates deep into the soil, to a depth of at least 24 to 36 inches so that the entire root zone is hydrated. The easiest way to give a large tree a deep root watering is to place either a sprinkler or a soaker hose over the tree’s drip line and let it run for about 2 hours, ensuring lots of water penetrates the soil. A deep root watering is much better than frequent shallow waterings which do not get moisture to the lower roots. During periods of extreme drought you may also want to consider spraying the soil around the tree’s root zone with Hydretain Root Zone Moisture Manager. This is a unique and advanced product specifically designed to assist a tree in dealing with drought stress. It works like a natural magnet to hold water near the tree’s root zone and keep the root zone hydrated during periods of drought stress.

What’s wrong with her redbud? | The Sacramento Bee

What’s wrong with this redbud? The leaves became mottled and started dropping in summer. The cause may be found at the tree’s roots. Mary Lowe

We planted an Eastern redbud tree in our backyard several years ago. Last year, I noticed that in late summer the leaves started getting mottled, yellowing and dropping. Bark was missing as well, but we blamed that on a toddler.

This spring, it looked quite healthy and didn’t even get much of a caterpillar infestation like it used to. However, as summer wore on, much more bark came off and no one was doing it. Plus the leaf discoloration and dropping became severe. I think all of the leaves that have dropped have been from disease and not seasonal change. What should I do for the tree?

Mary Lowe, Roseville

According to UC master gardener Mary Griggs, there are several possibilities for the problem with your tree, including root and crown rots and verticillium wilt, a soil-dwelling fungus that infects through roots, caused by pathogens promoted by excess soil moisture and poor drainage. Both result in leaves that fade, yellow, brown or wilt. Both may result in eventual death of your tree.

First, let’s look at verticillium wilt. In some, but not all plants, peeling back the bark on newly infected branches may reveal dark streaks following the wood grain.

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Many tree varieties are susceptible to this disease including redbud. Other trees that can be hit hard by verticillium wilt are maple, catalpa, persimmon, ash, golden rain, olive, pistache, elm, tulip tree, Southern magnolia and the whole Prunus family of fruit and nut trees – plum, apricot, peach, cherry and almond.

This disease also attacks many vegetable crops especially tomatoes, potatoes, cucumbers, pumpkins and melons.

Verticillium wilt may be managed by providing good cultural care for your tree. Provide proper irrigation, modest amounts of slow-release fertilizer and other appropriate care to promote new growth and increase chances of survival. If it becomes necessary to remove the tree, replace it with a plant that is resistant to verticillium wilt.

Among those trees that are very resistant or immune to verticillium wilt are birch, eucalyptus, dogwood, oak, willow, liquidambar, walnut, locust, mulberry, apple and most citrus species.

Root rot and crown rot are caused by Phytophthora cinnamomi and several other phytophthora species that commonly infect the roots and crowns of landscape plants. This mold can continue up the tree and may be the cause of your peeling bark.

Both these issues can be prevented – or at least minimized – when choosing and planting a tree in your landscape.

When planting a tree, the site should be prepared beforehand to provide appropriate conditions. Improve drainage at the site and only plant species that are not susceptible to phytophthora or verticillium wilt. It may help to plant your tree in a mound to facilitate drainage.

The bark issue is mostly likely connected to leaf drop. However, anthracnose will also cause premature leaf drop. Fruit tree leafroller will cause defoliation, too.

For a more specific diagnosis, have a trained arborist inspect your tree.

GARDEN QUESTIONS?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to h&[email protected] Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:

Sacramento: (916) 875-6913; 9 a.m.-noon and 1-4 p.m. Monday-Thursday

Amador: (209) 223-6838;

10 a.m.-noon Monday through Thursday; email ceamador. ucdavis.edu

Butte: (530) 538-7201;

8 a.m.-noon and 1-5 p.m. weekdays

Colusa: (530) 458-0570; 9 a.m.-noon and 1-4 p.m. Tuesdays; website: cecolusa.ucanr.edu

El Dorado: (530) 621-5512;

9 a.m.-noon Tuesday-Friday

Placer: (530) 889-7388;

Nevada: (530) 273-0919;

9 a.m.-noon Tuesdays through Thursday or leave a message

Shasta, Tehama, Trinity: (530) 225-4605

Solano: (707) 784-1322; leave a message and calls will be returned

Sutter, Yuba: (530) 822-7515; 9 a.m.-noon Mondays and Tuesdays and 1-4 p.m. Thursdays

Yolo: (530) 666-8737;

9-11 a.m. Tuesdays and Fridays, or leave a message and calls will be returned

More online

To read past Garden Detectives, go to sacbee.com/gardendetective

It all started with an email from a neighbor:

“Can you please provide me with some Master Gardener’s advice?” it read. “I’ve replaced the redbud trees on the south side of my property twice. The most recent tree I’d added now seems to be stressed. Am I overwatering? Too little water? Does it need fertilizer? We planted it in mid-May in a big hole, filled it with planting mix and tried not to plant it too deep. …”

This question did not come as a surprise. In the eight years that we’ve lived in our current Livermore home, I have observed that many of the redbuds in our area flourish at first, but then become weak and die.

These Eastern redbuds (Cercis canadensis) were planted by the builder, at the direction of the city of Livermore, in median strips filled with fescue. The trees are on drip irrigation systems, but they also get water from overhead emitters that water the fescue.

Redbuds are gorgeous deciduous trees, covered with small pink blossoms in the spring, followed by heart-shaped leaves after they’ve flowered. They have a classic “urn” shape and don’t grow too large.

Often their sisters, California redbuds and Oklahoma redbuds, are planted in our state, but for unknown reasons, Eastern redbuds were chosen for our location.

Solving a plant mystery is one of the things we master gardeners do. Since we are trained by the University of California, under its division of Agriculture and Natural Resources division, I went to one of the ANR publications, “Pests of Landscape Trees and Shrubs” (available to the public at http://ucanr.edu) to find the culprit.

And there it was, that nasty fungus known as verticillium wilt! My neighbor’s tree and those in the neighborhood show all the symptoms. The fungus affects the tree’s vascular system, preventing the delivery of nutrients and water. It causes the foliage to turn yellow and wilt. Shoots and branches begin to die on one side of the tree.

Verticillium wilt fungus resides in the soil. Keeping a tree vigorous, by providing proper irrigation and modest amounts of fertilizer, is the best way to increase its chance of survival. If chronic dieback occurs, dead wood should be eliminated by pruning. If a tree does die, only trees or plants resistant to verticillium wilt should be replanted in the area.

“Proper irrigation” is always difficult to gauge. But plants receiving water from both drip irrigation and overhead emitters are probably getting too much water. Young redbuds are particularly vulnerable to overwatering.

It would have been advisable to plant trees with ground covers that had the same watering needs here — perhaps a drought-resistant ground cover, with the drip system providing moisture for both.

My neighbor’s redbud might yet make it, especially with reduced watering and light fertilizer. If it doesn’t, she can select a new tree; a list of verticillium-resistant plants is available at www.ipm.ucdavis.edu/pmg/garden/plants/diseases/rstverticillium.html.

Shari Wentz is an Alameda County master gardener. For more information about the county’s three demonstration gardens and outreach programs, go to http://acmg.ucdavis.edu, call 510-639-1371 during business hours on Monday or Thursday, or email [email protected]

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