By Matt Gibson and Erin Marissa Russell
Persian shield is one of the most beautiful foliar plants that you will ever see in a garden. From a distance, its leaves are a brilliant deep purple hue, but upon closer inspection, The deep purple leaves are outlined with blue green edging and veinage, and the entire topside of the leaves have an iridescent metallic-silver sheen and are highly-textured. The combination is simply stunning. Though the plant is known to flower in the late fall or winter when provided with the right circumstances, the tiny, blue, tubular flowers are easily outshined by the stunning foliage that provides incredible color all year long.
Hardy to USDA zones nine through eleven and an evergreen in hot climates, the purple Persian shield plant is more commonly grown in the garden as an annual or indoors as a houseplant. Also known as royal purple plant, the bushy sub-shrub grows to three to four feet tall and two to three feet wide at full maturity. Though it is called the “Persian,” shield, the plant actually hails from Myanmar (formerly Burma). Well-suited to beds, borders, and containers, it’s no surprise how this perfectly purple tropical shrub has been championed by gardeners across the globe.
Varieties of Purple Persian Shield
The genus Strobilanthes has nearly 250 ornamental herbs and shrubs scattered throughout the continent of Asia. Commonly cultivated species within the genus range from small ground cover plants to large shrubs. The most commonly grown Strobilanthes species is the purple Persian shield, which displays gorgeous eight-inch leaves and can grow up to four feet high.
Growing Conditions for Purple Persian Shield
Purple Persian shield likes bright indirect light. It’s iridescent leaves grab the sunlight and reflect it back. If kept indoors, it needs to be exposed to bright lights in order to retain its brilliant coloration. Persian shield enjoys soil with a neutral pH range anywhere between 5.5 and 7.5. It will tolerate slightly acidic soil, but will not adapt to alkaline soil environments. Persian shield requires consistently warm temperatures that stay above 60 degrees Fahrenheit, as well as high humidity.
Though hardy to zones nine through eleven, Persian shield is more commonly found indoors or in beds as a summer annual in cool, temperate climates. In zone nine as well as in seven and eight during mild winters, the plant may die back to the ground after frost only to grow back in the following season. In zones 10 and 11, it can be grown as an evergreen and left outdoors year round. If you are growing Persian shield indoors as a houseplant, make sure to mist daily or use a humidity tray to maintain humid conditions at all times. Dry air can cause the plant’s leaves to dry out and drop to the ground. When misting, be sure to use soft water, as water with chlorine can damage the plant’s leaf tissue.
How to Plant Purple Persian Shield
Though Persian shields can be propagated by seed, finding seeds for the plant is next to impossible. Instead, multiply your purple Persian Shield collection by taking and rooting stem tip cuttings. Learn more about how to propagate Persian shield plants in the How to Propagate Purple Persian Shield section below.
Care for Purple Persian Shield
In fall or winter, the Persian shield plant may attempt to bloom. When it is grown as an annual, Persian shields often lack the time to worry with setting buds and flowering. However, the blooms that these plants produce pale in comparison to the leaves anyway, so gardeners won’t miss out on much. Houseplants typically flower in the wintertime, but you may want to pinch the blossoms off to encourage fuller, more bushy growth. Flowers are generally small and insignificant next to the stunning foliage’s intricate design and vibrant coloration.
Since it is grown primarily for its foliage, many gardeners will pinch back the leaves of the purple Persian shield as well, to help create a fuller plant. If left to its own devices, Persian shields can get tall and leggy, and can even flop over from overextension. Do not clip off the fading leaves that grow just after flowering. They may look a little sad at first glance, but that is due to the plant entering dormancy for the winter. Pruning after the plant has entered dormancy will disturb its rest. Resume pinching back efforts when the plant starts to show signs of new growth in the spring.
Persian shield will need more shade if it is not provided with enough water. Cold water irrigation can make spots on the leaves, so if you see spotting occur just after a rain, it is most likely due to cold rains, and not a sign of disease. If Persian shields are provided with a consistently moist soil base, they will only need light fertilization at the beginning of the growing season and one additional light feeding about halfway through the summer.
If you are growing purple Persian shield as a houseplant, trim back the plant occasionally to keep it at a manageable size. To help keep the plant’s size down, repot young plants every year until they reach full maturity, after which, plants will only need to be repotted once every two years. Another way to keep the size of older plants to a manageable size, is to prune the roots back when repotting. If your plant starts to look a bit leggy, take stem cuttings to start anew and retire the mother plant.
How to Propagate Purple Persian Shield
Purple Persian shield plants can either be propagated from seed or using cuttings. Keeping seeds in a location that stays between 55 and 64 degrees Fahrenheit (13 to 18 degrees Celsius) is required in order for them to germinate.
Softwood cuttings can be taken from mature plants in order to propagate the next generation. Cuttings are best taken in spring or early summer. Use clean, sterilized garden shears to snip off cuttings two to three inches long from the tip of the stems, making your cuts just below the nodes where leaves emerge from the stems. Remove leaves from the bottom half of your cuttings, then plant them in a soil-free growing medium such as peat. Mist the plant, then top it with a plastic bag to create a greenhouse effect for the cutting. This bag must be removed for an hour each day to prevent mildew. Roots will appear in a few weeks, at which point you can move the plant to its permanent home in potting soil.
Garden Pests and Diseases of Purple Persian Shield
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.