By: Mary H. Dyer, Credentialed Garden Writer
Rose of Sharon is a hardy plant that usually grows in difficult growing conditions with very little maintenance. However, even the toughest plants can run into trouble from time to time. If you notice your rose of Sharon has yellow leaves, you’re understandably perplexed about what has befallen this trusty late summer bloomer. Read on to learn a few of the most common reasons for rose of Sharon leaves turning yellow.
Poorly drained soil is one of the primary reasons for rose of Sharon leaves turning yellow. The moisture can’t drain effectively and soggy soil suffocates the roots, which causes drying and yellowing rose of Sharon leaves. You may need to move the shrub to a more suitable location. Otherwise, improve drainage by digging a generous quantity of compost or bark mulch into the soil.
Similarly, overwatering may be the culprit when leaves turn yellow on rose of Sharon (especially when overwatering is compounded by poorly drained soil). Allow the top 2 to 3 inches (5-7.5 cm.) of soil to dry, and then water deeply enough to soak the roots. Don’t water again until the top of the soil is dry. Watering in the morning is best, as watering late in the day doesn’t allow sufficient time for the leaves to dry, which may invite mildew and other moisture-related diseases.
Rose of Sharon is relatively pest resistant, but pests such as aphids and whiteflies may be a problem. Both suck the juices from the plant, which can cause discoloration and yellowing rose of Sharon. These and other sap-sucking pests are usually easily controlled by regular applications of insecticidal soap or horticultural oil. Remember that a healthy tree, properly watered and fertilized, is more resistant to infestation.
Chlorosis is a common condition that frequently causes yellowing of shrubs. The problem, caused by insufficient iron in the soil, is usually ameliorated by applying iron chelate according to label directions.
Inadequate fertilization, especially lack of nitrogen, may be the cause for rose of Sharon leaves turning yellow. However, don’t overdo, as too much fertilizer can scorch the foliage and cause yellowing. Excessive fertilizer can also burn the roots and damage the plant. Apply fertilizer only to moist soil, and then water well to distribute the substance evenly.
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Read more about Rose Of Sharon
Rose of Sharon flowering trees (Hibiscus syriacus) infuse the home garden with tropical-inspired beauty during summer with their colorful blooms. Blossoming in hues such as pink, red, purple and white, these small trees reach a mature height of up to 15 feet, though their height typically ranges from 6 to 12 feet with a spread of 4 to 10 feet. Due to its ease of maintenance and slow-to-moderate growth, this plant fares well in nearly any home landscape within U.S. Department of Agriculture hardiness zones 5b to 9a. However, when you notice symptoms of disease, act quickly to bring your Rose of Sharon back to health.
Provide optimal care to Rose of Sharon plants as healthy plants have a greater capacity for avoiding and overcoming disease than unhealthy ones. Trim back surrounding plants that create shaded conditions with pruning shears Rose of Sharon plants prefer full sun to partial shade.
Maintain moist, well-drained soil for best health.
Inspect Rose of Sharon trees regularly for abnormalities. Look for fallen buds if flower buds drop from plant, set a more consistent irrigation schedule and avoid creating extremes in watering. Do not let soil dry out completely between waterings and avoid creating waterlogged conditions.
Inspect leaves for round spots, a symptom of fungal or bacterial disease, such as the fungal disease cercospora leaf spot. Look for leaf drop as the disease progresses. Control this problem by removing affected plant parts with pruning shears and destroying them. Irrigate soil directly, rather than employing overhead irrigation, to keep plants dry moist conditions encourage the development of leaf spot diseases. Control severe problems by applying an appropriate fungicide with an active ingredient such as chlorothalonil or mancozeb.
Monitor Rose of Sharon plants for root rot problems such as the fungal disease cotton root rot caused by the pathogen Phymatotrichum omnivorum. Look for dried, discolored, brown leaves that do not fall from the Rose of Sharon tree. Search for decaying roots and the presence of a white, cotton-like fungal growth near the soil line. Control this soil-borne problem to avoid future disease or infection of other desired plants, as "attempts to control the disease with fungicides and soil fumigation have not been successful," according to the Oklahoma Cooperative Extension Service. Remove and destroy affected plants and replace with other resistant options.
I have a six-year-old Rose of Sharon (small, patio tree) in my garden that's looking distressed. We had a hard winter this past year, and one dead branch had to be pruned. It's blooming like always, but it looks different than usual. the leaves are small and scanty this year, so the branches look mostly bare.
Any thoughts or advice? Is this a normal reaction to a harsh winter? Will it gradually perk up on its own, or do I need to do something for it?
I think I'd try a solution of Epsom salt (magnesium sulfate) which seems to be beneficial for stressed leaves on many deciduous plants. Won't hurt to try it. The leaves already there won't increase in size but if the color intensifies you'll know the plant benefitted. Here's an interesting article about mgnesium and sulfur in the garden:
This message was edited Jun 20, 2007 10:35 AM
ds, look closely at the leaves and see if you see bugs or ants on them.If you see ants, the problem is likely aphids. I had horrible problems with mine. The leaves looked stippled/speckled and smaller than normal. It had tons of buds, but the blooms wouldn't open. Once they are stressed, they're more prone to insect and disease problems.They can have canker, aphids, bacterial leaf spot, etc. Here's a link that will help diagnose the problem. I hope this helps you figure out what's wrong.
Thanks Yuska and Crowelli. I keep epsom salts around for baths, so I'll try that. My tree (my whole garden, in fact) usually has small black ants roaming around, but they don't seem to damage anything. My tree is covered with full, open flowers it's just half-naked as far as the leaves go. Very strange. The leaves that are there seem smaller than usual.
Plants in our area are still recovering from the drought we've finally come out of (yahoo to that!). Rose of Sharons *love* a wet spring, and it sounds like yours has put all of its energy into blooming, instead of leafing out. No doubt a good dose of organic fertilizer and a few more sunny days will help immensely.
I don't think the problem is due to a cold winter. Finding a few dead branches can be normal occurrence. I prune my Rose of Sharon that are small trees before they start producing leaves in the spring. I cut the branches back by about 1/3 and some 1/2 back.. I do this so that the production of leaves, stems and flowers (they are larger also) is increased. The plants becomes more full. I cut out any dead branches afte it leafs out some. Due to my Mother being critically ill, I did not have time to do this before the leaves budded out. The one by the patio looks as you have described yours looking.
Also, Rose of Sharon are prone to cotton root rot. I have lost at least 3 to this problem. I lost another one that I early loved this spring due the amount of rain, because it was in an area that did not drain well and because I had to water it a lot the past 3 years during the drought. The leaves turn yellow and the bloom buds will fall off with too much or too little water. They do best in acidic soil. Also, is it receiving less sunlight than it did in the past? When my oak trees grew a lot over the years and the Rose of Sharon were then in shade for a long period of time during the day, they became spindly and not very bushy. I have found that they do best with morning sun and afternoon filtered shade. They tend to wilt in full sun when it becomes really hot in August. Try the other suggestions above, give it some low nitrogen fertilizer. At the end of winter next year, prune it back. You will be glad that you did. If you prune it now, you will be losing a lot of the blooms however, it will bloom later. In fact, .I have seen Rose of Shaon pruned as hedges.
I have gotten into the habit of creating a berm for each shrub or tree I plant. W/clay soil the plants just seem to thrive better. It doesn't have to be a large berm just big enough to contain the roots of whatever you are planting and the plant gets good soil to begin with and the roots have a chance to multiply. Just a suggestion.
I also do that in my flower beds for each plant. Just a little soil goes a long way.
Thanks. It's possible that it's getting a little less sun this year since my baby peach tree nearby has shot up. Hm, not sure what I can do about that offhand, but maybe the peach tree can be moved. It's only been in the ground for a year, and I don't think its root system has dug in very deep since it still tends to "tilt" after heavy winds. :)
Hi, dsmorris. I don't have an answer for you, but I have a 15-year-old Rose of Sharon, and I live in the same city, so ours are being exposed to the same conditions.
I prune mine a lot and always have. (If we let it be the large V-shaped shrub it would like to be, it would completely block the back door.) Heavy pruning has never bothered it at all. One year we got serious and cut off two or three main branches, big enough to need the chain saw. But the tree barely blinked. So I would not think that yours should miss one branch.
It did not seem to be affected at all by either the drought, or this year's wet spring. Its foliage is the same as always. We've pruned off the usual small branches, and have the same mass of flowers (and bumblebees).
Not saying that yours couldn't be affected by those things, but they do seem to be very hardy once established. You might want to look another direction.
Flower Bud Drop (physiological): Open flowers and buds may drop suddenly when one moisture extreme follows another. For example, drought stress followed by adequate moisture may cause such drop. Other extremes in growing conditions may also contribute. Avoid drought stress.
Leaf Spot (fungi – Cercospora spp., Phyllosticta spp. and others): Circular spots occur on leaves which results in their shedding from the plant. Use appropriate foliar fungicides to prevent damage.
Root Knot Nematodes (Meloidogyne spp.): Knots or galls form on roots causing the plant to be inefficient in absorbing water and nutrients. Leaves are small and the plants fail to make normal growth. Use caution when planting to be sure that planting stock is not infested. If yard soil is contaminated, plant shrub in a large container of sterilized soil. This is probably the most serious problem experienced by althea.
Cotton Root Rot (fungus – Phymatotrichum omnivorum): Althea is very susceptible to attack by the cotton root rot fungus that occurs in the soils of central Texas. If this disease is a problem in the area, it may be necessary to grow the plant in a large container of sterilized potting mix or soil.
Leaf Rust (fungus – Kuehneola malvicola): Infection by the leaf rust fungus causes chlorosis and leaf spotting. Infection is characterized by yellow-orange pustules on the lower leaf surface. Fungicide control is usually not necessary.
Is it pruned as a tree-form (aka Standard)? It looks like it is. I think they can be more finicky than when allowed to have multiple main branches.
It may be just suffering a little "transplant shock" and will perk up in a few days. It's usually best to plant them in the fall or early spring. Deep, weekly watering throughout the summer months or they will have leaf yellowing and drop then like hot potatoes. Add a 2-inch mulch layer to cool the soil temperature, reduce evaporation and prevent weeds. Browse at this link to The Gardner's Network for lots of good information.
Few pests damage these plants, with the exception of Japanese beetles and aphids. To control a small number of Japanese beetles, pick them off and drop them in a bucket of soapy water. If you see large numbers of these pests, look for an insecticide and follow the directions on the package label. Aphids can also be controlled with insecticides, and natural predators, like ladybugs, can help.
Rose of Sharon is typically deer-resistant, although very hungry deer will eat almost any plant.
When you water, try not to get the foliage wet. Fungal spores can grow on wet leaves and form brown spots that eventually kill them. If leaf spots show up, remove the damaged leaves and destroy them. Don't put them in your compost pile, where diseases can spread. You can also use a fungicide to control leaf spots.
Fungal spores can also cause cankers that ooze sap on rose of Sharon plants. Leaves can wilt or turn yellow and drop, and if not treated, the plants may die. Cut off any infected branches or replace your plant if the main trunk is infected. To avoid spreading the disease, clean your pruning tools between uses.
Plants with deceptive names carry an air of mystery that please some gardeners and annoy others. I, for one, love the fact that Rose of Sharon (Hibiscus syriacus) is neither a member of the rose family nor native to Syria. That means it’s not just a hardy hibiscus, but a plant with secrets. And you can’t beat those papery flowers that keep on coming just when we need them most!
Rose of Sharon plants aren’t tricky in their cultural requirements, but issues do come up. Here at Gardening Know How we do get some questions about these plants and love to help out. Here are the 10 most commonly asked questions about planting and caring for Rose of Sharon, so if your hibiscus isn’t thriving, you might be able to find the solution.
Ready to invite a Rose of Sharon shrub into your garden? The best time to transplant is fall. These are deciduous plants that lose their leaves in winter, but transplanting in fall, together with autumn rain, allows those roots to dig in well before the dead of winter.
What’s more disappointing than to have a hibiscus bush full of buds that just won’t open? Happily, the cause of this is usually cultural, which means an issue you can resolve. Rose of Sharon shrubs grow best in full sun. A too-shady location may work for younger shrubs, but too much shade can cause fungal issues and failure to flower in older plants. Irrigation can be an issue as well. Too much water can cause bud rot, while too little can also stifle flowering.
Rose of Sharon shrubs transplant without much fuss, so consider this for shrubs in the shade. When the plant is dormant, dig out its root ball including a couple of feet of soil, carry it to a new (sunnier) location, then water well. It will send down roots and regenerate in spring.
These hibiscus shrubs bud and flower on new growth. That means that the ideal time to prune a Rose of Sharon plant is soon after the blossoms have faded.
We adore these shrubs for their pleasing papery blossoms, but their easy-going ways are also extremely appealing. Hibiscus, in general, and Rose of Sharon, in particular, are self-cleaning and do not require deadheading. On the other hand, deadheading can reduce unwanted seedlings.
Every plant has its own particular limits in terms of temperature. Generally, Rose of Sharon shrubs thrive down to USDA hardiness zone 5, so if your zone is lower, your winter cold may kill off these shrubs. Even in zone 5 you may see winter damage. Sometimes, these plants are simply slow to leaf out, as they prefer warmer temps to do so. Patience is a virtue here. That said, you can do the scratch test just to be sure. Scrape off some bark to determine whether the stems are alive – green means yes, brown means no. If they are green, cut them back and see if they develop new growth.
It always feels a little like magic to replant a shrub from its own seeds. Look for lobed seed pods that develop after the blossoms fade. Each lobe holds at least three seeds. These seeds grow readily in moist, well-drained soil. In fact, you may get more seedlings than you want just under the bush, and these can be transplanted to a new bed.
Try to remember the morning after your last big move, how strange it felt to be in a new location. That’s the human equivalent of transplant shock. Recently transplanted shrubs may be feeling that shock which can cause dropping leaves or yellowing leaves. Water new transplants every few days for a while, then irrigate at least every week for the growing season.
I try to think of this as a form of divine justice: easy-care plants are often the ones that overrun the garden, spreading new seedlings far and wide. Rose of Sharon plants do seed easily and there’s no getting around the need for regular removal. Your best bet to control them is to hand-pull early and often and, for heaven’s sake, don’t put the seedlings anywhere near the compost.
You’ll find it remarkably easy to start new Rose of Sharon from softwood cuttings taken in spring. Remove all but the top set of leaves, then trim the cutting just under a leaf node. Put into moist, well-draining soil and cover with a plastic bag to hold in the moisture.
We all have questions now and then, whether long-time gardeners or those just starting out. So, if you have a gardening question, get a gardening answer. We’re always here to help.