Crepe myrtle leaves turning brown

Problems of Crepe Myrtle

Tree/shrub Tops Blacken, Die Back In Spring means Cold Weather
In some northern areas crape myrtles are victims of cold snaps which kill their tops. Their roots are generally cold hardy, however, so simply prune off the dead material early in the spring before growth starts. The plant will sprout new growth and bloom on schedule.
Crape myrtle Fails to Bloom indicates the plant was Pruned Too Late
Crape myrtles bloom on wood that is form in the current growing season. If pruning is delayed until the new shoots have begun to grow and they are cut off, flower buds will not form. The tree is basically all right and will bloom next season. Always prune before growth starts in the spring.
Foliage Curls, Turns Yellow shows Aphids
Check crape myrtle stems and leaves for bunches of soft-bodied, pear-shaped, insects a little bigger than the head of a pin. They may be white, yellow, red or brown. These are aphids, which suck sap from leaves and stems of crape myrtles, causing them to curl and turn yellow. As they feed they secrete a sticky “honeydew” on the foliage that coats it. It, in turn, encourages sooty mold fungus, which then coats the leaves in black.
To dislodge light aphid infestations, spray the undersides of foliage vigorously with water three times, once every other day, in the early morning. If aphids persist, spray them with insecticidal soap every 2 to 3 days, making sure to hit the insects with the spray. As a last resort, spray them directly with encapsulated pyrethrum. Take care to use pyrethrum late in the day to minimize killing honeybees and other beneficial insects that reside in the yard. If serious aphid problems recur every year, spray dormant oil spray on the crape myrtle trunks and stems late in the winter before leaves begin to develop. This will smother overwintering aphid eggs.
For more information see file on Controlling Aphids.
Leaves Stunted; Coated With White Powder indicates Powdery Mildew
This fungal disease is a serious problem on crape myrtles from Maryland to Florida and out to Texas and in the North on trees planted near the seashore or other cool, foggy areas. It also sometimes strikes these plants which are in shady locations. It winters over in dormant buds and shows small white circles on new leaves when spring arrives. Then it spreads to new, young shoots and eventually to the larger leaves. Affected plant parts are coated with a dusty white growth and the leaves are stunted and thickened. Sometimes they are only 1/3 normal size. Stems are stunted, flower buds fail to develop. Diseased plant parts sometimes drop off in a week or two and the plant may recover and produce new growth when hot weather arrives. Where powdery mildew is common, spray trees with lime sulfur in early spring as the buds break. Repeat this spray 2 weeks later. If the infection persists, spray all affected plant parts with wettable sulfur or dust with sulfur. Plant in open, airy locations with plenty of sun. Mildew resistant varieties of crape myrtle are hybids `Biloxi’, `Miami’, and `Wichita’.
For more information see file on Controlling Fungal Disease.
Leaves Near Stem Tips Turn Brown shows Tip Blight
A tip blight caused by a fungus sometimes attacks crape myrtles. Leaves near the branch tips turn brown in late spring or early summer. Tiny black spore-bearing bodies appear on infected leaves. Spray plants with copper fungicide or lime sulfur fungicide when symptoms first appear and then every 10 days in wet seasons. Avoid overhead watering which keeps foliage moist and fosters the disease. Prune to increase air circulation around plants, taking care to sterilize pruning tools by dipping them in household bleach to avoid spreading the disease. Because the fungus spores collect on the mulch beneath the shrubs, removing the old mulch and replacing it with fresh material may help prevent an outbreak from recurring.
If this blight is a common problem every year, prune and destroy affected plant parts in the early spring. Spray a copper fungicide or lime sulfur in four applications: (1) after the dead leaves and dying branches have been removed and before growth starts in the spring; (2) when growth is half completed; (3) after spring growth has been completed; and (4) after fall growth stops. Take care to determine if the crape myrtle twigs are turning brown from frost damage rather than disease.
For more information see file on Controlling Fungal Disease.
]Dead Blotches on Leaves means Leaf Spot
Various leaf spot fungi cause yellow, brown or black dead blotches on crape myrtle leaves. These blotches frequently run together. Heavily infected leaves then turn yellow or brown and fall prematurely. Cool, moist weather encourages these diseases, especially when new leaves are developing. Shake out all fallen and diseased leaves from the center of the crape myrtle and destroy them. Remove all dead branches from shrub centers, especially in crape myrtle hedges to allow better aeration. Mulching helps prevent the disease from splashing up from the ground and infecting plants. Spray at weekly to 10-day intervals with sulfur or Bordeaux mixture or other copper fungicide, particularly if weather is damp. Spray between rains. Dig up and discard seriously infected shrubs with their root system and soil ball in a bag for the trash. Clean up all debris, infected leaves, etc. to avoid spreading the fungus.
For more information see file on Controlling Fungal Disease.

Yellowing Crepe Myrtle Leaves: Why Are Leaves On Crepe Myrtle Turning Yellow

Crepe myrtles (Lagerstroemia indica) are small trees with abundant, showy blossoms. But the lush green leaves help make this a favorite in gardens and landscapes in the southern United States. So if you suddenly spot leaves on crepe myrtle turning yellow, you’ll want to figure out quickly what is going on with this versatile plant. Read on for information about what might be causing yellow leaves on a crepe myrtle and what action you should take to help your tree.

Crepe Myrtle with Yellow Leaves

Yellowing crepe myrtle leaves are never a very good sign. You’re used to gorgeous dark foliage, exfoliating bark and abundant blossoms on this usually trouble-free tree, so it’s alarming to see leaves on crepe myrtle turning yellow.

What is causing the yellowing crepe myrtle leaves? It could have one of several causes, each requiring a slightly different remedy. Keep in mind that if this yellowing takes place in autumn, it is normal, as the foliage begins prepping for dormancy with leaf color changing yellow to orange or red.

Leaf Spot

Your crepe myrtle with yellow leaves may have fallen victim to Cercospora leaf spot. If the spring was very rainy and the leaves turn yellow or orange and fall, this is likely the issue. There is no real point in trying fungicides against this type of leaf spot since they are not very effective.

Your best bet is planting the trees in sunny spots where air circulates freely. It will also help to clean up and pack out infected fallen leaves. But don’t worry too much, as this disease won’t kill your crepe myrtle.

Leaf Scorch

Bacterial leaf scorch is a big bad problem that causes leaves on crepe myrtle to turn yellow. Look for the yellow appearing first at the tips or leaf margins.

If your crepe myrtle has bacterial leaf scorch, remove the tree. You should burn it or otherwise dispose of it to prevent the spread of this fatal disease to healthy plants.

Physical or Cultural Damage

Anything that damages the trees may cause yellowing crepe myrtle leaves, so this could be any source of toxicity in the environment. If you’ve fertilized or sprayed the crepe myrtle or its neighbors, the problem could be excessive nutrients, pesticides and/or herbicides. Assuming good drainage, watering it well will often help move the toxins out of the area.

Other cultural problems that cause yellow leaves on a crepe myrtle include inadequate sunshine and too little water. If the soil doesn’t drain well, it can also result in crepe myrtle with yellow leaves.

QUESTION: This spring we planted a crape myrtle that produced good green growth. Now many of the leaves are browning at the tips. What does the plant need?

ANSWER: A little time is likely all the crape myrtle needs to establish a root system that can supply the water needs of the foliage. The tips of the leaves are farthest from the source and the last to get the moisture. During hot weather, young trees may not be able to absorb the water needed, and the ends of the leaves turn brown.

You can help the crape myrtle get through the hot, dry weather by watering two to three times a week until the root system grows into the surrounding soil. Good establishment of the plant could take from six months to a year. The return of the rainy season should help with watering and prevent further browning of the foliage.

Q: Our camellia plant has produced an egglike fruit containing several seeds. How are these planted to start new shrubs?

A: Wait until the fruits start to turn brown to collect the seedpods from the camellia. Inside are several thick-walled seeds that can be sown to produce new plants.

Prepare the seeds for planting by putting a hole in the surface to allow water and air to enter. Most gardeners nick an edge of the seed with a knife or file away a small area of the thick outer coat.

Sow the seeds in a 4- to 6-inch-deep container. Use a light potting soil and space each seed several inches apart. Cover the seeds with about one-quarter to one-half of soil, and water to begin the germination process. The seeds grow roots, then foliage in about four to six weeks.

Q: Our garden’s tomatoes have been a disappointment. They have formed large cracks that radiate from the stems, and they have a thick, tough, colorless core. Why?

A: Few gardeners produced great tomatoes this year. The problems you describe, as well as thick skins, seem to have happened because of the late, cool winter followed by an early hot summer.

Tomatoes like a long period of warm weather to mature their crop. Extremely cold or hot weather appears to ruin the quality of the fruits. All varieties appear to be giving the same performance.

Now that the rainy season has arrived, you can expect more cracking problems as well as rot. Perhaps the fall plantings to be started in mid-August can produce a better harvest.

Q: I am getting a late start, but I’d like to add a citrus tree to the landscape. Is summer too late to plant it?

A: Thanks to container-grown trees, it’s never too late to add a citrus tree or any other landscape plant to the yard. Make sure the new addition gets a sunny location away from buildings and tall trees, and you are ready to plant. Keep the soil moist and begin light but frequent feedings through October.

Q: Is it possible to grow grass in a very shady area? I have planted sprigs, plugs and seed, but all perform poorly.

A: Some areas of the landscape are just too shady for grass. Of all the turf types, some of the St. Augustines do the best. Varieties to try in the shade include Bitter Blue, Delmar and Seville. Even these cannot grow in the dense shade.

Where grass won’t grow, try some shade-tolerant ground covers. A few of the best include cast iron plant, ferns, English ivy, liriope, mondo grass, Asiatic jasmine and wandering Jew. None take the foot traffic like grass, but they do add greenery to the landscape.

Tom MacCubbin is the urban horticulturist at the Orange County Cooperative Extension Service, a division of the Institute of Food and Agricultural Sciences at the University of Florida. Write to him in care of The Orlando Sentinel, MP-6, P.O. Box 2833, Orlando, Fla. 32802.

Forsythias – Bright Yellow Harbingers of Spring

Iowa State University Extension

After a long, drab winter, most gardeners anxiously await the arrival of spring. One sure sign that spring has truly arrived is the bright yellow flowers of the forsythia. Named after William Forsyth, an 18th century Scottish horticulturist, the forsythia is a deciduous shrub that is native to China, Korea and Europe.

In Iowa, forsythias typically bloom in early to mid-April. The four-petaled flowers vary from light yellow to bright golden yellow and persist for 10 to 14 days. Flowers are produced in groups or clusters along the stems. Forsythias bloom only on old wood.

Leaves emerge shortly after flowering. Forsythia leaves are medium to dark green in summer. Fall leaf color is usually poor. Occasionally, however, leaves may turn pale yellow to reddish purple in fall. Forsythias are one of the last deciduous shrubs to drop their leaves in fall. In Iowa, leaf drop typically occurs in late October or early November.
Forsythias are fast growing shrubs. Many cultivars (varieties) have spreading, arching growth habits and can reach a height of 8 to 10 feet.

Forsythias grow and bloom best in full sun. They will grow in partial shade, but won’t bloom as heavily. Forsythias adapt to a wide range of soils. However, they do not perform well in wet, poorly drained sites. Forsythias do not have serious insect or disease pests.

The forsythia is an excellent plant for mixed shrub borders. It can also be massed on sunny slopes or used as an informal hedge. Low-growing cultivars can be used as groundcovers.

When selecting a forsythia, choose a cultivar that reliably blooms in Iowa. The flower buds on some cultivars in Iowa are not reliably cold hardy. For example, the flower buds on ‘Lynwood Gold’ and ‘Spring Glory’ are hardy to -10 degrees F. Since most parts of Iowa experience winter temperatures below -10 degrees F, these cultivars often don’t bloom well in the state.

An excellent forsythia for Iowa is ‘Meadowlark.’ Jointly introduced by North Dakota State and South Dakota State Universities, in collaboration with the Arnold Arboretum, ‘Meadowlark’ will bloom after exposure to temperatures down to -30 degrees F. Flowers are bright yellow. ‘Meadowlark’ is a vigorous, rapidly growing shrub. Its height and width are 8 to 10 feet. ‘Meadowlark’ has a spreading, arching form.

‘Northern Sun’ is another good choice for the upper Midwest. Introduced by the University of Minnesota, ‘Northern Sun’ will flower after temperatures drop to -30 degrees F. The spreading, arching shrub grows 8 to 10 feet tall and has a similar spread. Flowers are yellow-gold.

Introduced by Iowa State University, ‘Sunrise’ is an excellent cultivar for southern and central Iowa. Its flower buds are hardy to -20 degrees F. Plants are covered with masses of small, medium yellow flowers in early spring. ‘Sunrise’ is a semi-spreading, compact shrub with a mature height and width of 5 feet. Its compact size makes ‘Sunrise’ ideal for small hedges or shrub borders.

Other forsythia cultivars that bloom well in Iowa include ‘Northern Gold,’ ‘New Hampshire Gold’ and ‘Vermont Sun.’

While most forsythia cultivars are grown for their attractive yellow flowers, a few are grown for other features. ‘Bronxensis’ is a low-growing cultivar that is often used as a groundcover. Plants commonly grow 18 to 24 inches tall. Unless covered by snow, ‘Bronxensis’ doesn’t usually bloom well in Iowa as its flower buds are hardy to -10 degrees F. Gold Tide(R) is another low-growing forsythia. The compact, spreading plant grows 2 to 3 feet tall. Its flower buds are hardy to -15 degrees F. Gold Tide(R) is commonly used as a groundcover and foundation planting. ‘Fiesta’ is a compact shrub with variegated foliage. Plants typically grow 3 to 4 feet tall. Leaves are green with yellow centers.

Forsythias are easy to grow, but do require some maintenance. Pruning is the most important chore. Proper pruning produces healthy, vigorous, heavily blooming shrub. Since they bloom on old wood, forsythias should be pruned immediately after flowering. Pruning the shrubs from mid-summer to late winter will drastically reduce flowering in spring.

When pruning mature forsythias, it’s best to remove one-fourth to one-third of the oldest (largest) stems at ground level every other year. New shoots will emerge from the ground and bloom in following years. Old, neglected forsythias can be rejuvenated by pruning them back to within 3 to 4 inches of the ground in late winter or early spring. The rejuvenated shrubs will grow back quickly and should begin blooming again in one or two years.

Some shrubs provide multi-season interest with attractive flowers, fruits or foliage. While the forsythia is rather one-dimensional, its yellow flowers are a beautiful, welcome sight in the spring landscape.

A high resolution version of the above photo is available for media use. forsythia.jpg (504k)

When it comes to golden foliage some of us just can’t get enough. These 10 favorites have been the best and brightest in the garden and will help your garden glitter with yellow and golden-colored hues.

‘Katsura’ Acer palmatum

Acer palmatum ‘Katsura’ by Joann Currier

We know it is spring when the vivid gold palmate leaves of our ‘Katsura’ Japanese maple frame the patio garden. This is one of the first trees to leaf out so the radiant canopy commands attention. It does best in morning or filtered sun. ‘Katsura’ is stunning in fall turning bright yellow with orange tones.

‘Sun King’ Aralia cordata

Aralia cordata ‘Sun King’ by Joann Currier

‘Sun King’ aralia is a great new fast-growing perennial from Japan offering bold yellow compound leaves that light up a part-shade garden. It grows quickly to 3 to 4 feet and is deer-resistant and drought tolerant. ‘Sun King’ makes a brilliant tropical splash that is hard to resist.

‘Everillo’ Carex oshimensis

Carex oshimensis ‘Everillo’ by Joann Currier

‘Everillo’ is a bright and exciting new grass for shade with striking gold foliage. This evergreen sedge is a sport from the popular carex ‘Evergold’. Growing 1 foot tall by 2 feet wide, the plant is great as a single accent or en mass. In the shade garden, ‘Everillo’ is a fantastic year round grass that will grow on you. Try it in a container for great color.

‘Verdoni’ Chamaecyparis obtusa

‘Verdoni’ is a bright gold dwarf Hinoki cypress for sun or part sun. This slow-growing conifer has an appealing pyramidal shape with flattened horizontal branches. The dense twisting foliage is radiant in the winter garden. Reaching 3 to 5 feet in 10 years, ‘Verdoni’ is ideal for a container or that special spot at the front of the border.

Golden Spirit Cotinus coggygria

Cotinus coggygria Golden Spirit by Joann Currier

Golden Spirit is the bright yellow form of the more common burgundy smokebush. The foliage makes a big splash in the sun garden as it emerges lime green and matures to brilliant gold in the fall. This drought tolerant deciduous plant can be grown tree-form or kept pruned as a multi-branched 6-foot shrub. The beautiful round leaves absolutely glow in the garden.

‘Florida Sunshine’ Illicium parviflorum

Illicium parviflorum ‘Florida Sunshine’ by Joann Currier

‘Florida Sunshine’ anise is an elegant evergreen with bright chartreuse-gold foliage that is the perfect accent in part sun. This medium sized deer resistant shrub was selected and introduced by Tony Avent of Plant Delights Nursery in Raleigh. Reddish stems become prominent in fall offering an interesting contrast with the foliage. This wonderful shrub grows to 4 feet tall and wide.

Fiona Sunrise Jasminum officinale

Jasminum officinale Fiona Sunrise by Joann Currier

Fiona Sunrise jasmine is our new favorite vine! It has gorgeous bright gold foliage that really stands out twining up our evergreen holly. Fragrant white flowers adorn this deciduous vine in mid-summer. Fiona Sunrise grows best in morning sun and will climb 12 feet in one season.

‘All Gold’ Juniperus conferta

Juniperus conferta ‘All Gold’ by Joann Currier

‘All Gold’ shore juniper continues to be our favorite low juniper in the garden. This fast growing conifer with bright yellow foliage reaches 1 foot tall by 4 feet wide in three years. This colorful groundcover combines well with many shrubs and always makes the garden pop.

‘Golden Ghost’ Pinus densiflora

Pinus densiflora ‘Golden Ghost’ by Joann Currier

In our scree garden ‘Golden Ghost’ red pine is a standout. Visitors are drawn to this evergreen conifer with its electric yellow needles with subtle green banding. This dense slow growing pine will develop into a beautiful 6 to 8 feet tall specimen in 5 years. With sun and good drainage ‘Golden Ghost’ will become the center of attention.

Goldy Thuja plicata

Thuja plicata Goldy by Joann Currier

Resembling the flame of a large candle, Goldy arborvitae is a radiant conifer with perfect compact form. It is a very heat tolerant evergreen that thrives in full sun with good drainage. Goldy works well as a specimen in the garden or in a large container. This slow grower will take many years to reach its mature height of 15 feet.

Byline:

Joann Currier gardens near Chapel Hill and is the owner of The Unique Plant, a specialty nursery. You can reach her at

Perplexed by yellowing leaves on trees, plants and shrubs?

Posted on: August 7th, 2017

Outdoor plants which appear to be stressed are common along Colorado’s front range during the summer months. From plants and turf, to shrubs and trees – they are all affected by something called chlorosis (yellowing leaves).

Chlorosis is a term that describes a lack of chlorophyll (green pigment) in the leaf. Chlorophyll is the energy production engine in the plant. Along Colorado’s front range, the most common causes of chlorosis include alkaline soils (high pH) and hot summer temperatures.

Soils

Alkaline soils (high pH) account for much of the chlorosis issues in Colorado. High pH soils are negatively charged. Iron particles are positively charged. As you may remember from chemistry class – opposites attract. Therefore, iron binds to highly alkaline soils.

While ample iron exists in our soils, it is chemically bound to the soil particles and less available to the plants. Plants that are chlorotic from a lack of iron may be green early in the spring, but become chlorotic as iron is depleted.

Temperatures

Excessive heat exacerbates chlorosis.

In the soil, extremely warm temperatures may slow root growth – especially on shallow rooted trees and shrubs. In the canopy, foliage is cooled by evaporating water on the leaf surface. However, as air temperatures continue to rise, this cooling system may not be able to keep up.

When heat becomes extreme or the plant becomes drought stressed, the foliage will essentially overheat. At this point, chlorophyll production slows and the leaves become yellow (scorched) and will eventually turn brown.

What can you do about yellowing leaves?

Introduce iron treatments into your landscape.

Treatments include foliar, trunk injection and soil treatments.

Foliar (spray) iron treatments may be done any time plants are in leaf. The foliar treatments are short lived requiring multiple applications per year.

Trunk treatments involve putting iron into small holes drilled into the tree. Results are often favorable, but the procedure is invasive for the tree.

Soil treatments for trees and shrubs are best completed in spring for the current year or fall for the following growing season. Make sure to use a chelated iron (chelation keeps the iron from being bound to just the soil and available for the plant as well).

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