Leaf Drop On Oleander – Reasons For Oleander Dropping Leaves

Leaf Drop On Oleander – Reasons For Oleander Dropping Leaves

By: Bonnie L. Grant, Certified Urban Agriculturist

Oleander plants are drought tolerant, old-fashioned southern garden gems. These toxic beauties produce breathtaking floral displays and are easy to maintain. There are several possible reasons for an oleander dropping leaves. If leaf drop is combined with yellowing, damaged foliage, signs of insects or other issues, it is easier to narrow down the causes. Cultural conditions, pests, disease and even herbicide drift can all cause oleander leaf drop. Read on for some possible causes and solutions to leaf drop on oleander.

Cultural Causes of Oleander Leaf Drop

Oleanders are more common in warm regions but can withstand winters in temperate zones. They are hardy to 35 degrees Fahrenheit (1.6 C.) and have remarkable drought tolerance once established. The best blooms come from plants in full sun and well-drained soil with average water application. If you are providing these conditions and still wondering, “Why is my oleander losing leaves,” we may be able to provide some answers.

Too much water and too little water can cause yellowing leaves and leaf drop. In the summer, water the bushes 1 to 2 times per week, deeply. Make sure your plant is in well-draining soil. Soggy roots can be a cause of leaf drop on oleander.

Oleanders don’t need a lot of fertilizer, but in poor soils or in containers where nutrients are limited, apply a balanced food in spring to perk up your plants.

Oleanders have extensive root masses but where planted with other competitive plants they can begin to get sickly and foliage can suffer. Move the bushes if they are sited too closely to a large tree or in an area with binding, thick growth at the root zone.

Oleander Dropping Yellow Leaves from Pests

One of the most common causes of many plant ills are insect pests. If you see your oleander dropping yellow leaves, it could be a sign of a pest invasion. These tiny invaders can do a lot of damage with their feeding activity. Sucking insects are particularly bad, and they are most active in hot weather. A species of aphid and one of scale are particular to oleander.

If you can’t spot the aphids, look for sticky honeydew or sooty mildew on the leaves. Both are a sign of their presence, as are ants, who feed on the sweet honeydew. Heavy infestations can be blasted off with water or you can use a horticultural oil spray.

Scale will appear as whitish bumps on the stems of the plant and can also be combated with horticultural oil applied 3 times over the course of 6 weeks.

Oleander Leaf Scorch

Oleanders are quite trouble free in most cases, but there is a serious disease that affects plants (mainly in California). Oleander leaf scorch is caused by Xylella fastidiosa bacteria. This disease is primarily caused by insects called glassy winged sharpshooters and others species in the group. The effects can be devastating.

It starts by causing a blockage of the water and nutrients to the roots. The results are gradually yellowing leaves, which eventually die and drop off.

The disease has no cure, but pruning off the affected areas can slow the disease and help prevent it from spreading to neighboring oleanders. Destroy the infected plant parts. Do not put them in your compost pile. Sadly, over time you will lose your oleander but good care and removal of infected material can prolong the life of the plant.

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Why Are Oleanders Dying?

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A favorite shrub in southern areas, oleander (Nerium) produces deep green leaves with a leathery texture and tubular clusters of flowers in shades of pink, red, white or apricot. This summer blooming, evergreen shrub is hard in U.S. Department of Agriculture hardiness zones 9 through 11 where they are grown as lawn specimens, hedges and screens. The shrub is fairly easy to maintain, but is susceptible to few pests and disease that can kill it.


Why are my oleander leaves turning yellow?

Too much water and too little water can cause yellowing leaves and leaf drop. In the summer, water the bushes 1 to 2 times per week, deeply. Make sure your plant is in well-draining soil. Soggy roots can be a cause of leaf drop on oleander.

Secondly, what's wrong with my oleander? Oleander plants are susceptible to bacterial infections, particularly oleander knot disease and the potentially fatal bacterial leaf scorch. Although plants usually survive the infection, the disease causes unsightly galls and dieback on stems, bark and leaves.

Besides, how often should I water my oleander?

They like to be watered as much as you would water your shade trees – deeply every three days. To aid in water retention, create a reservoir or dike that is 2-4 inches tall around the trunk of the tree.

Why are my oleanders dying?

Oleander leaf scorch is the reason the leaves on these long-lived shrubs are drooping, turning brown and dying. Individual branches die back then, as more branches are affected, the entire plant dies. The disease takes its toll rapidly when the plants are stressed by heat and lack of rainfall.


Huber: Oleander leaves yellow, drop off

Q. Some of the leaves on our oleanders are turning yellow and dropping. The plants also are a little spindly. When should they be pruned, and how far can we safely cut them back?

A. Yellow leaves can be a sign of too little, too much or inconsistent water. Make sure the soil drains well. If the roots are sitting in wet soil, the foliage will yellow and drop.

Watering heavily after a dry period, too, can trigger yellow foliage.

Some oleander varieties flower in spring, while others flower spring through summer. Prune after the flowering period and by the end of August or early September so new growth stimulated by pruning will have time to "harden" before winter.

Oleanders naturally have a billowy, globular shape that requires little pruning. Remove broken, weak or dead branches. Remove an unwanted stem at ground level or where it joins an older stem.

A rule of thumb: Prune no more than a third of the existing foliage. Carefully prune stems for a balanced look.

Plants become spindly when they grow toward the light. Full sun encourages a full, bushy plant and the best blooms.

Drought-tolerant once established, oleanders tolerate the alkaline, sandy soils in Galveston, as well as the heavier soils here. And they thrive in a compost-enriched, well-draining soil.

Oleanders generally need little or no fertilizer. Established plants with light-green foliage and/or few flowers will benefit from an application of a balanced fertilizer in early spring and another in early fall. Water well after fertilizing.

Q. I plant tomatoes in an 8-by-12-foot garden each spring. A friend told me that I would not get a tomato crop this year due to tomato plants being planted there year after year. I compost, fertilize and add bonemeal to the area after the plants have been removed each year. Should I alternate my tomato plants each year in such a small area?

A. Rotating crops does help discourage soil-borne diseases and nematodes. Experts recommend that tomatoes or any other member of the nightshade family (which includes potato, pepper and eggplant) not be planted in the same area any more often than once every four years.

But many of us have small spaces that don't easily allow for much rotation. When possible, move tomatoes annually among raised rows within a small garden space. And plant the most disease-resistant varieties.

You've probably improved your odds against disease by adding organic matter to your soil. If your plants look healthy and are flowering and setting fruit, I imagine you'll be eating tomatoes before long. Consider rotating next season.

Q. How would I grow `Soo Yoh' cucumbers? Where can I get seed?

A. `Soo Yoh Long' (or `Suyo Long') is a sweetly flavored Chinese cucumber and a favorite among serious vegetable gardeners here. Heat-tolerant, it is sown in a slightly acidic, well-draining soil mid-March through summer. Provide a trellis so the long, slender fruit will grow straight.

Harvest the burpless cucumbers before fully mature. They're delicious sliced or pickled.

If you can't find seed locally, order from Johnny's Select Seeds, 800-879-2258 www.johnnyseeds.

Q. Where might I find seed for winter melon, `Soo Yoh Long' cucumbers and snow peas?

A. See above for the cucumber seed source. You might check local Asian markets for winter melon and other vegetable seed.

Seed for winter melon, various cucumbers, snow peas, yardlong beans and other Asian vegetables can be ordered from Evergreen Y.H. Enterprises, P.O. Box 17538, Anaheim, CA 92817 714-637-5769 www.evergreenseeds.com.

Q. Earlier you wrote about a new hydrangea that flowers longer than the traditional types. What was this plant?

A. It is a new mophead, `Endless Summer.' As with other mopheads, soil alkalinity or acidity affects the color of the blooms. The flowers will be pink in more alkaline soils, blue in acidic soils. But unlike traditional types, this new variety flowers on new wood and is being touted as having a long blooming period.

I planted four `Endless Summer' in the fall, and two have just begun to bloom, so I'm not sure how long this variety will flower here. The plants look healthy.

Ask your nurseryman about availability. I have seen it at one or two nurseries. This plant is being grown by Greenleaf, a wholesaler in El Campo, as well as Flowerwood, the Alabama grower that developed Encore azaleas.

Mail garden questions to Kathy Huber, Garden Editor, Houston Chronicle, P.O. Box 4260, Houston, TX 77210. We regret that the bulk of mail prevents individual replies to each unpublished letter.

Kathy Huber has worked for the Houston Chronicle since May 1981. She was Features Copy Desk chief before becoming the first full-time garden editor for the paper in 1988. She writes a weekly garden Q&A and feature stories.

A Texas Master Gardener, she's the author of The Texas Flower Garden, published by Gibbs-Smith in 1996. She's been a frequent speaker at various garden events.

A native of Moultrie, Ga., she graduated from Queens University of Charlotte, formerly Queens College. She did graduate work through the University of Georgia system.

She is married to photographer John Everett and they have one son.


Varieties of Oleander

  • 'Hardy Pink': Pink flowers relatively cold-hardy 8 to 15 feet tall and 6 to 10 feet wide
  • 'Mathilde Ferrier': Double pale yellow flowers 8 to 15 feet tall and wide
  • 'Mrs. Lucille Hutchings': Large cultivar double peach-colored flowers 20 feet tall and 10 feet wide
  • 'White Sands': Dwarf variety white flowers 4 to 6 feet tall and wide
  • 'Petite Salmon': Dwarf variety salmon pink flowers 4 to 6 feet tall and wide
  • 'Hawaii': Large pink flowers with yellow throats 10 to 18 feet tall and up to 12 feet wide

What does it mean when oleander leaves turn yellow?

Oleanders, contrary to some popular opinions, like to be watered deeply and about as often as you would water your shade trees. Watering every day is too often. At this time of year you should water them deeply about every three days.

Secondly, what's wrong with my oleander? Oleander plants are susceptible to bacterial infections, particularly oleander knot disease and the potentially fatal bacterial leaf scorch. Although plants usually survive the infection, the disease causes unsightly galls and dieback on stems, bark and leaves.

Similarly, why is my oleander losing leaves?

Too much water and too little water can cause yellowing leaves and leaf drop. In the summer, water the bushes 1 to 2 times per week, deeply. Make sure your plant is in well-draining soil. Soggy roots can be a cause of leaf drop on oleander.

How do you revive an oleander?

To prune oleander annually, snip off new shoots at the base of the plant in late summer or early fall to shape your plant and stimulate healthy growth. Moreover, if your plant has gotten too tall, cut the stems to half the height you'd like it to be. For example, if you want a 4 foot plant, cut it back to 2 feet.


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