As an annual, Persian shield is usually planted from potted nursery starts in spring after the soil has fully warmed. It grows relatively fast in warm, humid conditions; a small potted nursery plant will become a bushy 2-foot plant within a few weeks. Grown in the garden, Persian shield performs well in warm conditions in locations with dappled sunlight, if given plenty of moisture. Failure is usually traced to conditions that are too dry or too cold. Potted nursery starts should not be planted outdoors until the soil is well warmed and nighttime temps remain reliably above 50 degrees Fahrenheit. Grown as annuals, these plants usually do not flower before winter cold sets in, and most gardeners don’t worry about flowers, pinching back the plants early to encourage bushy growth and more foliage. Indoors, the plant may flower in winter, but the flowers tend to be small and are outshined by the leaves.
Light
In its native environment, Persian shield is found in dappled light conditions on the edges of tropical forest clearings, and it will do best in gardens that mimic this environment. Persian shield accepts full sun in cooler climates when grown as an annual, though partial shade is best suited for showing off the shiny foliage. The color can appear a little washed out in full sun. If kept indoors, it needs plenty of bright light—even some direct sun—to keep its color.
Soil
Persian shield grows well in the neutral range of soil pH and can tolerate slightly acidic soil. Keep the pH between 5.5 and 7.5.
Water
The less water the Persian shield plant gets, the more shade it will need. The plant will quickly droop if it doesn’t receive adequate water, but it typically bounces back quickly after a drink. A full 1 inch of water per week is a minimum for garden plants, but very hot conditions may require daily watering to avoid leaf wilt.
Temperature and Humidity
Persian shield does best in warm temperatures (above 60 degrees Fahrenheit) and sultry humid air. It is fully evergreen in USDA zones 10 and 11, and can grow as a standard perennial in zones 8 and 9, where it dies back to the ground but usually returns in the spring. Elsewhere, it can be grown only as an annual, though a very good one. Even in warmer climates, this plant is often used as an annual rather than perennial. If growing indoors, make sure it has humid conditions. Dry air will cause the leaves to dry and drop. Misting daily is recommended, but be sure to use soft water, as chlorine will damage the leaves.
Fertilizer
If grown in rich soil with plenty of moisture, Persian shield should only need light feeding at the start of the season and again about midway through the summer. For potted plants, the recommendation is to give them light feedings (half-strength) every two to four weeks. As with most foliage plants, nitrogen is the more important nutrient. Use a fertilizer formula that is weighted toward nitrogen, such as a 12-6-6 mixture. For the amount, follow the label instructions.
Types of Persian Shield
There are no named cultivars of Persian shield to choose from. However, Strobilanthes is quite a large genus containing more than 350 species, there are other species used as garden plants, though they can be difficult to find in the garden trade:
Strobilanthes alternata, also known as Hemigraphis alternate, is commonly known as the waffle plant. It is a prostrate plant with purple leaves, often grown as an annual ground cover or houseplant. It is also hardy only in zones 10 to 11. There are several cultivars of waffle plant to consider, including ‘Belgian Waffle’, ‘Red Flame Ivy’, and ‘Snow White’.S. maculates is a native Himalayan species with silver-splotches leaves.S. lactates is a Brazilian species with white blotched leaves.
Pruning
Since Persian shield is grown for its foliage and the flowers are not particularly showy, many gardeners like to pinch back the leaves to create a fuller plant. If left to grow on its own, it can get tall, leggy, and floppy. With indoor plants, do not remove the fading leaves that develop immediately after flowering. The leaves may look sad at this point, but that is because the plant has gone dormant for the remainder of the winter. Resist the temptation to pinch at this point, to avoid disturbing dormancy. Resume pinching when the plant starts growing in earnest in the spring.
Propagating Persian Shield
Plants can be started very easily with stem cuttings, using a procedure common to many tender perennials. Spring and early summer are the best times to take cuttings, though it is sometimes done in fall in order to start new plants indoors for the following spring. Here’s how to do it:
How to Grow Persian Shield From Seed
Seed propagation is not common for this plant, as the seeds can be hard to come by. Commercial seeds are not readily available, though you may be able to find specialty seed companies or seed exchanges that do offer them. It is also not easy to collect your own seeds, as Persian shield plants grown as garden annuals usually don’t flower in time to produce seeds. It’s possible, though, that indoor plants may flower in winter, providing you with an opportunity to collect seeds left behind as the flowers fade. If you can obtain them, plant the seeds in spring, or start them indoors in late winter. Seeds require somewhat warm conditions (55 to 64 degrees Fahrenheit) to germinate.
Potting and Repotting Persian Shield
Persian shield lends itself well to container culture. Any material will do, provided it has good drainage. Use a fairly large pot (at least 10 inches in diameter and height), and fill it with a standard peat-based potting mix. For indoor use, pinch back frequently to keep the plant to a manageable size instead of letting it grow to its full capacity. But even with this, you should plan to repot every couple of years, performing hard root-pruning each time to control the size. If your plant becomes too leggy or woody, take stem cuttings and discard the mother plant. It’s common for Persian shield to begin to experience diminished foliage color after it has bloomed. You may want to discard the mother plant and propagate new stem cuttings at this time.
Overwintering
When grown as annuals, the entire plant is generally pulled from the ground and discarded as cold weather approaches. Or, you can dig up entire plants, pot them, and and grow as houseplants through the winter. You can always move them back outdoors in the spring. Use a standard peat-based potting mix when transplanting garden plants into pots. The approach of cold weather is also a good time to take stem cuttings to root indoors for starting new specimens to plant outdoors in spring. If you are attempting to grow Persian shield as a garden perennial, a thick layer of mulch will help the roots survive the winter. This is possible only in zones 8 to 11.
Common Pests and Plant Diseases
Persian shield is not usually susceptible to fungus disease or other problems with the foliage, except water stress and spotting. Aphids and whiteflies can become pests, especially when the plants are drought-stressed. Insect pests are more common for indoor potted plants; control them with horticultural oil.
How to Get Persian Shield to Bloom
When grown as an annual, Persian shield may not have enough time to set buds and flower, but you will not miss them with all the colorful foliage. If you live in a warm zone where it can be grown as a perennial, or if you grow it as a houseplant, Persian shield often blooms in winter. But the flowers are not very showy, so most people aren’t concerned if the plants refuse to bloom. Should you need the plants to bloom in order to collect seeds for propagation, make sure to give potted indoor plants plenty of water and sunlight.
Common Problems With Persian Shield
Persian shield is an easy plant to grow, but there are some common problems you might encounter:
Color Fades
This plant is grown because of the colorful foliage, so is can be disappointing if the color fades or isn’t as vibrant as you expected. Normally, this happens because conditions are not warm and humid enough, or if the plant is growing in too much direct sunlight, which can wash out the leaf color. It is also natural for the plant’s color to fade somewhat after it has flowered—this is common with indoor potted plants. Many people choose to discard the mother plant and propagate new plants through stem cuttings when this happens.
Plants Flop Over
Although Persian shield likes dapped shade, it can become quite leggy if it gets no sun at all, leading to plants that flop over. Pinch back the stems frequently to make the plant bushy and discourage legginess. Increasing the amount of sunlight can also help reduce legginess.
Leaves Wilt
Persian shield needs a lot of moisture, and in hot weather you might find yourself watering daily—or even twice daily—to keep the leaves from collapsing. Fortunately, the plant readily recovers, even from intense wilting. Potted plants growing indoors during dry winter months will also need frequent watering.
