By: Bonnie L. Grant, Certified Urban Agriculturist
Chances are pretty good you have seen this attractive foliage plant at nursery centers. The bright leaves of the Persian shield plant (Strobilanthes dyerianus) are almost better than a flowering specimen since they provide stunning color year around. Growing Persian shield plants requires warm temperatures and sultry humid air. It is hardy in USDA zones 8 to 11, but is more commonly grown indoors or as a summer annual in cooler climates. Use Persian shield indoors to brighten up the home and create tropical ambiance with ease of care.
Persian shield is a phenomenal foliar specimen. It produces 4- to 7-inch (10 to 18 cm.) long, slender leaves tipped with a point. They are slightly serrated and have deep green veins with purple to silver on the entire surface of the leaf.
The plant has a bushy habit and may get up to 4 feet (1 m.) tall in habitat. Because it is only suitable for USDA zone 10, growing Persian shield indoors is the best way for most gardeners to enjoy this brilliant plant. You can put the plant outside in summer, but make sure you bring it back inside before cold weather threatens and you may be rewarded with slender spiky flowers.
The plant performs well in a container inside or outside, in full sun to partial shade. Provide even moisture and high humidity. The best way to give extra humidity to a Persian shield indoors is to place a thin layer of rocks in a saucer and balance the pot on top. Keep the saucer full of water. This keeps the roots out of the water but the evaporation of the water provides higher humidity to the air.
You can grow Persian shield outdoors in warm climates and plant them in the ground as part of a border display. In cool zones, however, treat the plant as an annual or bring it inside at the end of summer.
You can share this lovely plant easily with friends and family. Persian shield propagation is done through seed or cuttings. Take 2- to 3-inch (5 to 7.5 cm.) sections from the tips of the plant, cutting just below a growth node.
Strip the bottom leaves off and insert the cutting into a non-soil medium such as peat. Mist the medium and place a bag over the cutting. Remove the bag for one hour daily to keep the cutting from molding. In a couple of weeks, the cutting will produce roots and you can replant it in potting mixture.
Persian shield is an easy-to-care for plant. Pinch the stems back to force bushiness.
Water the plant when the top couple of inches (5 cm.) of soil are dry and keep a bit drier in winter.
Fertilization is one of the most important Persian shield care instructions, especially for potted plants. Feed every two weeks with a half dilution of liquid plant food. Suspend feeding in fall and winter.
Watch for mites and soil gnats. You can combat these with horticultural soap and by changing the soil.
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If you enjoy plants with decorative foliage, you might have encountered the Persian shield plant (Strobilanthes dyerianus). Known for its iridescent purple leaves, it's a tropical plant native to Myanmar that grows outdoors year-round in U.S. Department of Agriculture plant hardiness zones 8 through 11, although it might die to the ground during winter in colder parts of this range. It also does well as an annual or a houseplant elsewhere, and needs only ordinary care to thrive.
Persian shield loves humid climates, making it a perfect choice for summer gardens in Florida. It will perform best if it's planted in a rich, well-drained soil that receives regular watering. Here in Florida, it's best to plant it in partial to full shade.
The stems can sometimes get tall and flop over, so it's a good idea to pinch the plant a few times early on to help create more branching.
Persian shield is cold tender, so gardeners should cover it when cold weather strikes. The other option is to treat the plant like an annual, replacing it in the spring if it doesn't grow back from its roots.
Persian shield can also be propagated from cuttings, so it makes a great passalong plant.
For more information on Persian shield, contact your county Extension office.
The Persian shield is not a particularly difficult plant to grow, providing you can give it the warmth and moisture that it needs. In colder conditions, the plant will drop leaves, and if you live in a place with colder winters, you might want to cut the plant down to the soil level to overwinter. It will grow back from the soil level provided it was not frozen. The main challenge with Persian shield is likely to be keeping the plant a suitable height for indoors.
Persian shield plants are not particularly susceptible to pests but can be affected by mealybugs, aphids, and mites. Signs of infestation include tiny webs on plants, clumps of white "powdery" residue, or visible insects on the plant. Treat infestations as soon as possible to prevent them from spreading to the rest of your collection.
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Purple Persian shield plants can struggle with a few pests, although they are not especially susceptible to infestation. Incredibly, diseases do not impact purple Persian shield plants at all. If your plants develop an insect problem, consider only using fertilizers that do not contain nitrogen (or those that only contain a small amount of nitrogen) to avoid making the problem worse. Examine your purple Persian shield plants carefully on a regular basis so that if pest issues do occur, you’ll know about it as soon as possible, leaving you poised to roll out the treatment plans we recommend below.
Aphids: Tiny aphids feed on the liquids inside plant leaves, sucking out the juices and leaving the foliage distorted, curled, or withered before it eventually falls from the plant. In addition to their feeding damage, you may also see the insects themselves on plants that are infested. Where aphids are feeding, you’ll also find the substance they secrete called “honeydew,” which is clear, sticky, and attracts ants. Aphids can also spread viruses, which result in discolored or mottled leaves and stunt the growth of the plants they infect.
Aphids come in a variety of colors and can be winged or wingless, but all of them are quite small and gather on the underside of plant leaves, where they can be spotted with relative ease. If you notice aphids or aphid damage on any of the plants in your garden, you should isolate them away from the other plants, or you risk spreading the infestation.
You can treat aphids by hosing down any infested plants, as the spurt of water from the garden hose will knock these tiny bugs right off the plant. However, you’ll need to repeat this treatment several times in order for it to work. You can also make homemade sprays to keep them at bay. One recipe soaks peeled onion pieces and garlic cloves in water with a bit of cayenne pepper. This mixture can be kept in the refrigerator for up to one week. You can also make a neem oil spray out of a liter of warm water, four or five drops of dish soap, and a teaspoon of neem oil. However, be aware that this treatment will also have negative effects on your population of beneficial insects, so keep its use to a minimum and opt for other treatments when possible. To learn more details, read our article All About Aphids, and How to Kill Them.
Fungus Gnats: While fungus gnats may simply seem like a nuisance, their larvae feed on the roots of plants. Plants with root system damage due to the larvae’s feeding may have stunted growth, leaves might droop or fall from the plant, and the plant may eventually die. The tiny insects are black or brown with two wings, and they look a lot like fruit flies. You may see them hovering near your plants or crawling along the surface of their soil.
Reduce the risk of your plants hosting fungus gnats by keeping extra moisture to a minimum, as they’re attracted to overly wet soil or any standing water that may be found near your plants. Ensure that soil drains properly and plant containers have holes to let excess moisture escape. Simply adding a layer of sand on top of your potting soil that’s an inch or two thick can resolve the conditions that attract these bugs. You can also use yellow sticky traps to catch the adults. If infestation is suspected, check the soil near plant roots for the wiggling white larvae. If you find them, rinse the excess soil (and any larvae) from plant roots before repotting them with a fresh new batch of sterile soil. To learn more details, read our article How to Get Rid of Fungus Gnats.
Mealybugs: Mealybugs don’t resemble the typical insect. Instead, they look like cottony flecks of white stuck to your plants. Stave them off by being careful not to overwater or overfertilize. You can also use a cotton ball soaked with rubbing alcohol, rubbing it over affected plant foliage, to treat a mealybug problem. To learn more details, read our article How to Fight Mealybugs.
Spider Mites: Spider mites aren’t actually mites, but they are tiny little spiders, as proven by the webbing that appears on the underside of plant leaves where mites have set up shop. If you see this webbing, remove it, as the mites use it to travel from plant to plant, and it can also prevent treatments from reaching the insects. The mites themselves appear to the naked eye as tiny white or red dots that move around.
You can treat an infested plant by giving it several rounds of targeted blasts from the garden hose, but don’t expect to see results until you’ve repeated this treatment on multiple occasions. You can also treat for spider mites with an alcohol-soaked cotton ball or the neem oil spray we described in the section about aphids above. To learn more details, read our article How to Fight Spider Mites.
Whiteflies: Whiteflies are small white insects with wings that, like aphids, cluster on the underside of plant foliage. Unlike aphids, however, whiteflies will take flight if you run your thumb along the area where they sit. Another similarity they share with aphids is that they feed on the juices inside plant tissue, so affected plants will exhibit wilting. They also become weak from lack of photosynthesis, and their growth may be stunted, while foliage can turn pale or yellow.
Like many other pests of purple Persian shield plants, you can treat a whitefly problem with a cotton ball soaked in rubbing alcohol, rubbed gently along the plant’s foliage. Several rounds of jets from the water hose will knock them off the plant, though repeated treatments are required for this method to be effective. You can also release predatory insects to fight them off, including one simply called the whitefly parasite, lacewing larvae, or ladybugs. To learn more details, read our article How to Fight Whiteflies.
The purple Persian shield plant is an excellent choice for gardeners at any experience level because of its resistance to disease and the small chance of pest insects, all of which are treated rather easily. Its vibrant foliage makes it a unique yet attention-grabbing choice, whether nestled among other plants in a garden bed or placed in a prominent location as a houseplant. When it’s cared for carefully in gardens in southern climates, you may be lucky enough to see its gorgeous blue blooms as well. You can find purple Persian shield plants at just about any nursery, garden center, or online supplier, so don’t hesitate—add one to your collection today.