If you’re not familiar with rose mallow, get ready to be amazed, especially if you garden in a northern climate. This often overlooked native perennial offers all the exotic floral beauty of tropical hibiscus (Hibiscus rosa-sinensis) but is tough enough to overwinter outdoors in areas as far north as Minnesota.
Like tropical hibiscus, rose mallow boasts huge, vibrantly colored flowers, some growing to the size of dinner plates. But once your hardy hibiscus bursts into bloom, it will continue flowering until the first frost and then return again in spring for a repeat performance. Despite its tolerance for cold weather, rose mallow also loves the heat and grows equally well in balmy southern climates.
Common rose mallow, swamp mallow, swamp hibiscus, dinner plate hibiscus; also shares the common name hardy hibiscus with Hibiscus syriacus.
Fast. New growth is slow to emerge from dormancy in spring, but plants shoot up rapidly once they take off, growing as much as an inch per day.
Mostly native to swampy areas, rose mallow prefers evenly moist, humus-rich soil. If necessary, mulch to help retain moisture.
Midsummer until the first frost. Although the flowers only last a day or two, rose mallow is a prolific rebloomer.
Broad, triangular, and deeply lobed. Usually medium green, but some cultivars have deep purple, coppery red, or blue-tinged foliage.
The vibrant purple foliage and delicate red blooms of the African mallow shrub (Hibiscus acetosella) make it a prized ornamental plant However, fungal diseases can sometimes plague these tropical shrubs, causing unsightly damage and impeding healthy growth If your African mallow shows signs of fungal infection, taking prompt action is key to clearing up the problem and restoring the plant’s beauty. This article covers effective techniques for eliminating different types of fungus on African mallow shrubs.
Identifying Common Fungal Diseases
Accurately diagnosing the type of fungus impacting your African mallow is the critical first step. The main fungal diseases that infect these plants include:
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Powdery mildew – Recognizable as a white, powdery coating on leaves and stems. This fungus thrives in humid conditions.
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Leaf spot – Causes distinct dark circular spots, often with yellowing halos, on the foliage.
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Root rot – A severe fungal infection of the roots leading to wilting and dying foliage
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Botrytis blight – Identified by fuzzy gray mold on flowers, buds, and stems in very humid weather.
Closely inspect your plant and match the symptoms to identify the specific fungal disease present before treating. Catching it early maximizes your chance of success.
Cultural Practices to Prevent Fungal Growth
Implementing good horticultural practices is the first line of defense against fungal diseases on African mallow shrubs:
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Ensure excellent drainage and avoid overwatering.
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Allow adequate air flow and light penetration with proper spacing and pruning.
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Water at the base of plants, not from overhead.
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Promptly remove and dispose of fallen leaves or debris.
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Promote overall plant health with optimal sunlight, water and fertilization.
Following these simple cultural practices creates an environment less favorable for fungal pathogens to take hold in the first place.
Applying Chemical Fungicide Treatments
If fungal infection already exists, chemical fungicides specifically formulated for ornamental plants can be very effective. Always carefully follow label directions. Options include:
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Neem oil – Derived from the neem tree, this organic fungicide smothers fungal growth and spore production.
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Copper-based products – The copper in these fungicides combat fungal diseases. They may leave a blue-green residue.
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Chlorothalonil – A synthetic fungicide that prevents fungal spore germination and growth. Avoid breathing spray mist.
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Tea tree oil – The antifungal compounds in tea tree oil make it a useful natural fungicide treatment.
Test any product on a small area first to ensure the plant tolerates it well before widespread use. Repeat applications may be needed for stubborn fungal diseases. Avoid spraying in hot sun or excessively rainy conditions.
Organic Fungicide Options
For a non-chemical approach, these organic homemade sprays can suppress fungal growth:
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Baking soda spray – Dissolve 1 tbsp baking soda + 1⁄2 tsp liquid soap in 1 quart water. Spray on leaves.
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Milk spray – Mix 1 part milk with 2 parts water and spray foliage. The lactose creates antifungal compounds on leaf surfaces.
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Garlic oil spray – Blend 4 cloves garlic with 1 tbsp mineral oil. Strain and dilute with 1 pint water.
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Vinegar spray – Use a 5% white vinegar and water solution to control powdery mildew.
Thoroughly coat the leaves, stems and buds with these organic sprays. Reapply every 7-10 days as needed. They create a protective fungicidal coating while being gentle on plants.
Sterilizing Tools and Pruning Out Infection
To limit spread of fungal spores, always sterilize pruning tools after working on an infected plant by dipping in a 1 part bleach to 9 parts water solution. When pruning, cut well below visible disease, getting into healthy tissue. Remove and destroy all diseased plant material. Avoid composting.
Improving Soil Health
For cases of root rot, improve drainage and introduce beneficial microbes by amending surrounding soil with compost. You may need to remove the plant, treat the root system, and replant in fresh, enriched soil.
Consistent Prevention and Early Action
While challenging to completely prevent, staying vigilant and responding quickly at first signs of infection gives the best chance of overcoming fungal diseases on African mallow shrubs. Don’t allow fungus to persist untreated. Employ a multifaceted approach combining good cultural practices, proper identification, effective fungicide spraying, tool sterilization and overall plant health promotion as needed to keep your African mallow lush and vibrant.
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Summerific® Berry Awesome rose mallow. Photo by Proven Winners.
If you’re not familiar with rose mallow, get ready to be amazed, especially if you garden in a northern climate. This often overlooked native perennial offers all the exotic floral beauty of tropical hibiscus (Hibiscus rosa-sinensis) but is tough enough to overwinter outdoors in areas as far north as Minnesota.
Like tropical hibiscus, rose mallow boasts huge, vibrantly colored flowers, some growing to the size of dinner plates. But once your hardy hibiscus bursts into bloom, it will continue flowering until the first frost and then return again in spring for a repeat performance. Despite its tolerance for cold weather, rose mallow also loves the heat and grows equally well in balmy southern climates.
On this page:
Common rose mallow, swamp mallow, swamp hibiscus, dinner plate hibiscus; also shares the common name hardy hibiscus with Hibiscus syriacus.
3 to 8 feet tall, 2 to 5 feet wide
Fast. New growth is slow to emerge from dormancy in spring, but plants shoot up rapidly once they take off, growing as much as an inch per day.
Mostly native to swampy areas, rose mallow prefers evenly moist, humus-rich soil. If necessary, mulch to help retain moisture.
Midsummer until the first frost. Although the flowers only last a day or two, rose mallow is a prolific rebloomer.
White, pink, red, or bi-colored, often with a contrasting eye.
Broad, triangular, and deeply lobed. Usually medium green, but some cultivars have deep purple, coppery red, or blue-tinged foliage.
What to look for when purchasing rose mallow plants:
When shopping for rose mallow, look for plants labeled as indeterminate, which indicates that the flowers are produced all the way up and down the stems and not just at the tip, like determinate varieties. Indeterminate bloomers, such as those in the Summerific® series from Proven Winners, will produce flowers for months on end, giving you a longer season of interest. Summerific® plants are not prone to setting seed, which can be a big plus if you don’t want your plants to self-sow in the garden.
Summerific® Perfect Storm hibiscus. Photo by: Proven Winners.
In spring or fall, as long as there is no danger of frost.
In full sun (at least 6 hours daily). In hot climates, it may be necessary to provide some afternoon shade to prevent scorching of the foliage. Also provide shelter from strong winds, which can damage the delicate, crepe-papery flowers. Because of rose mallow’s preference for wet soils, it thrives in low spots and wetter areas along streams or ponds. However, it will tolerate a wide range of soil types if kept well-watered.
Start seeds indoors in early spring and then transplant outdoors once the weather warms or purchase potted plants from a nursery. When planting, be sure to give plants plenty of elbow room to accommodate their eventual spread. If necessary, amend sandy or poor soil with compost or other organic matter before putting your plants in the ground.
Because of its colossal blooms, rose mallow makes a bold statement wherever you plant it, so be sure to use it judiciously so it won’t steal the show from the other plants in your garden. It’s best used as a backdrop for sun-loving groundcovers or plants with strappy foliage that will add nice textural contrast to the broad leaves. Get more ideas for good companion plants to grow with rose mallow.
Use in combination with spring bloomers such as creeping phlox or Jacobs Ladder. Since hardy hibiscus are late to emerge, plants like these can carry the workload for the first half of the year.
Water regularly and up to twice a day in hotter weather, especially if growing in a container. Wilting leaves are a sure sign that your plant needs a good soaking. To avoid leaf fungus and other foliar diseases, water during the early morning hours rather than late in the evening.
Once new growth appears in spring, sprinkle a slow-release organic plant food around the root zone and then supplement with a water-soluble plant food in early summer, when the buds begin form, to boost flower production.
When properly planted and cared for, you can get many flowers from one rose mallow plant (shown is Summerific® Cranberry Crush). Photo by: Proven Winners.
When you see new growth begin to emerge in spring, prune back the old woody stems to about 6 inches tall to make way for the new foliage. To stimulate branching and promote a bushier habit, you can prune the tips of the branches in early summer.
Deadheading of spent blooms isn’t necessary unless you want to prevent seedpods from forming.
In colder climates, apply a layer of mulch around your plants after they die back in the fall to provide an extra layer of insulation. While plants are dormant, water only enough to keep the soil moist.
Rose mallow growing in a pot can generally be left outdoors unless temperatures are expected to drop below 20 degrees F for a prolonged period of time. During a cold snap, take precautions by moving the pot to an unheated interior space, such as a garage or garden shed, until the temperatures warm up again.
Particularly vulnerable to Japanese beetles and sawflies. Leaf fungus can also be a problem but is easy to control by maintaining good air circulation around the plant and by removing diseased leaves.
Prevent & Treat Powdery Mildew and 4 Home Remedies that Work!!
FAQ
How do you get rid of shrub fungus?
What is the fungus on mallow?
Can plants recover from fungus?
Does vinegar get rid of plant fungus?
How do I get rid of Mallow weed?
Getting rid of this persistent plant is not an easy chore either. Mature mallow seems to be incredibly resistant to most common herbicides. One of the best ways to control this weed in lawns is to make sure your turf is thick and healthy. A healthy turf will choke out the weed and not allow the seeds to spread.
How much water does African Mallow need?
African mallow needs 0.8 cups of water every 9 days when it doesn’t get direct sunlight and is potted in a 5.0″ pot. Use our water calculator to personalize watering recommendations to your environment or download Greg for more advanced recommendations for all of your plants. Does your plant get direct sunlight?
How do you control a mallow plant?
Controlling mallow can definitely be a frustrating task at best. Pulling, hoeing, or weeding works well when plants are very young and you must keep a constant eye to keep up on them.
Is African Mallow easy to care for?
African mallow is generally considered an easy-to-care-for plant and makes a great choice for beginners! African mallow prefers for the soil to dry out between waterings and should be watered regularly.