Persian Shield: How To Grow Outdoors or as a Houseplant

Strobilanthes, also commonly known as Persian shield, is an annual plant or herbaceous perennial, depending on the climate. It is called a "Persian shield" because it looks like a little pointed armor shield ready for battle, with a flashy, purplish iridescence and a silvery metallic sheen.

Persian shield is native to Myanmar, not Persia, as its name implies. It grows best in tropical climates with dappled light, ample moisture, and consistent temperatures above 45°F.

Persian Shield Care

Here are the main care requirements for growing a Persian shield:

• Requires warm growing conditions with dappled sunlight and moist, slightly acidic soil.
• Grows in full sun in northern climates, although it prefers partial sun in warmer, hotter climates.
• Only plant outdoors when the soil has warmed, and nighttime temperatures remain above 50°F.
  
• Pinch back plants to encourage bushier, healthier growth.
• Give nitrogen-rich fertilizer at the beginning of the growing season and again midway through the season. If potted, give fertilizer more frequently (once or twice a month).

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.

When grown annually, Persian shields require full sun in cooler climates, though partial shade is best for showing off the shiny foliage.The color can appear a little washed out in full sun.

However, when grown 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. If it doesn't receive adequate water, the plant will quickly droop, but it typically bounces back quickly after a drink. Give at least 1 inch of water per week for plants grown outdoors, but very hot conditions may require daily watering to avoid leaf wilt.

Temperature and Humidity

Persian shield is a very popular garden annual and potted houseplant in colder regions. It does best in warm temperatures (above 60°F) and sultry, humid air. It grows like an evergreen subshrub in regions without winter frost, where temperatures remain above 45°F. In the transitional areas (zones 8, 9), it sometimes grows as a root-hardy perennial, dying back to ground level in winter and returning in spring.

As a houseplant, Persian shield tends to bloom during winter. However, the vibrant purple color often fades with age, and both outdoor perennials and indoor potted plants are usually discarded after a few years.

As an annual, the Persian shield is usually planted in a potted nursery in spring after the soil has fully warmed. Nighttime temps should remain reliably above 50°F. It grows relatively fast in warm, humid conditions; a small potted nursery plant will become a bushy 2-foot plant within a few weeks.

If growing indoors, make sure it has humid conditions. Dry air will cause the leaves to dry and drop. Misting daily is recommended, but 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 critical nutrient. Use a fertilizer formula weighted toward nitrogen, such as a 12-6-6 mixture. For the amount, follow the label instructions.

Where to Plant

If growing outdoors in a warm climate, plant Persian shield in a partial sun location, mimicking the filtered light of a plant growing under the tropical forest canopy. If outdoors in a cooler, northern climate, you can give it a full sun location. Indoors, provide Persian shield plants with a southern window for the brightest sun exposure. Ensure indoor plants get consistent moisture and regular fertilizer.

Types of Persian Shield

The benefits of growing Persian shield include its beautiful foliage, low maintenance care, ease of pollination by attracting pollinators, and pest resistance.

Strobilanthes is quite a large genus containing more than 350 species. There are no named cultivars of Persian shield to choose from. But here are some common types:

• Strobilanthes alternata, or Hemigraphis alternata, is 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-splotched 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 pinching the leaves to create a fuller plant. It can get tall, leggy, and floppy if left to develop independently.

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 to start new plants indoors for the following spring. Here's how to do it:

1. Use sharp pruners to snip a 3-inch cutting from a healthy stem just below a node.
2. Remove the leaves from the bottom of the cutting.
3. Plant the cutting in a small container filled with peat moss, moisten the potting medium, and place the container in a loosely secured plastic bag to hold in humidity. Set the pot in a bright location, but not in direct sunlight.
4. Each day, loosen the plastic bag for an hour or so to let the plant breathe, then spray with a mister before securing the plastic bag again.
5. The cutting should develop roots within a few weeks, and new growth will begin. At this point, remove the plastic bag and grow the cutting in a bright, warm location, watering frequently.
6. Alternatively, you can put the cutting in a glass of clean, filtered water in a bright, warm location. Change the water every two to three days. Roots should begin to form in one week. After three weeks of root formation, replant the rooted cutting in a moist potting mix.
   

How To Grow Persian Shield From Seed

Seed propagation is uncommon 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 challenging to collect seeds, as Persian shield plants grown as garden annuals usually don't flower in time to produce seeds. However, indoor plants may flower in winter, allowing you 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 warm conditions (55°F to 64°F) to germinate.

Potting and Repotting Persian Shield

Persian shields lend themselves well to container culture. Any material will do, provided it has good drainage. Use a relatively large pot (at least 10 inches in diameter and height) and fill it with a standard peat-based potting mix.

Indoors, pinch back frequently to keep the plant manageable 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 typical for Persian shields to experience diminished foliage color after they have bloomed.

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 grow them 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 an excellent time to take stem cuttings to root indoors to plant new specimens 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 fungal 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

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 are small and do not outshine the leaves.

When grown as an annual, Persian shield may not have enough time to set buds and flowers. However, you will not miss them with all the colorful foliage. If you live in a warm zone, they can be grown as a perennial or houseplant.

If you need the plants to bloom to collect seeds for propagation, give potted indoor plants plenty of water and sunlight.

Common Problems With Persian Shield

Persian shield is an easy plant to grow. If the plant fails to thrive, check the soil moisture first and ensure the temperature is warm (above 50°F). Here are some common problems you might encounter:

Color Fades

This plant is grown for its colorful foliage, so it 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. When this happens, many people discard the mother plant and propagate new plants through stem cuttings.

Plants Flop Over

Although Persian shield likes dappled shade, it can become quite leggy if it doesn't get any sun, 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, give it water 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.

From: thespruce