How to Grow and Care for Persian Shield

Strobilanthes dyerianus

Persian shield, Strobilanthes dyerianus, is a stunning ornamental species that originates in warm, humid Myanmar, where it grows as a tender evergreen perennial.

It is a member of the Acanthaceae family, which consists mostly of flowering tropical flora.

With its unique iridescent purple leaves, S. dyerianus had no difficulty attracting the attention of US gardeners, and is now grown here as an annual, perennial, and houseplant.

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In this article, you will learn all you need to know to cultivate this delightful tropical foliage outdoors in USDA Hardiness Zones 10 to 11.

It may also be grown as an indoor houseplant in all locales.

Here’s what we’ll cover:

Tropical Persian shield, aka royal purple plant, thrives on heat and humidity, yielding its most brilliant color in bright, indirect sunlight and partially shaded locations.

It prefers temperatures above 60°F.

The characteristic broadleaf foliage positively shimmers. Neon shades of purple veined with green seem to be overlaid with a silver gloss.

The growth habit is upright with leaves that are lance-shaped and measure six to eight inches long.

Stems are soft and may exceed three feet in height. Over time, they may become woody.

Small, tubular, cone-shaped blue flowers, reminiscent of Virginia bluebells may bloom in season, but these are a rarity.

The reason is not entirely understood, but is believed to be an example of “masting” behavior, in which blooming is sporadic, but profuse when it occurs.

This botanical phenomenon makes it impossible for wildlife to depend upon the seeds for food, as they are not always available.

In cooler regions, Persian shield grows as a summer annual, often failing to exhibit its most vibrant color, and dying off with the first frost.

With its vivid silvery-purple hues, Persian shield makes a bold perennial statement in warm-region gardens.

Place it in containers with trailing lime green sweet potato vine, pink snapdragon, and silvery green dusty miller.

And plant it on the sun-dappled fringes of gardens overflowing with ferns and snake plants, where their green textures make the purple foliage stand out dramatically.

Indoors, it’s quite a conversation-piece where the temperature is at least 60°F, the sun is indirect, and the moisture is ample but not excessive.

How to Grow

In Zones 10 to 11, you can cultivate your plant year-round in the ground or in outdoor containers.

If you are in Zone 8 or 9, you may find that the foliage withers and dies at season’s end, but the roots remain alive and sprouts appear again each spring.

For those of us in cold zones, like me, this species grows as an annual that dies back in its entirety, roots and all, and doesn’t return.

Be sure to take mature dimensions into account when growing in the garden or outdoor containers.

Plants need between one and three feet to spread out, and a soil depth of about 12 inches to support healthy root development.

For container gardening, use a good quality, organically-rich potting soil and a container with adequate drainage holes and a depth of at least 12 inches.

Keep the soil moderately moist by watering when the top third of the soil feels dry to the touch.

A moisture meter can help you to gauge when water is needed. Indoor pots may need water more than once a week, so check daily.

Amend the soil as needed with organically-rich compost or aged manure to achieve a loamy consistency that drains well and has a pH in the range of 5.5 to 7.5.

Water weekly in the absence of rain, using a moisture meter as your guide.

Fertilize at planting time and midway through the growing season, using a liquid plant food diluted to 50 percent.

Where to Buy

Persian shield is available in nurseries and online for both indoor and outdoor cultivation.

With diligent care of a quality starter plant, you can achieve mature dimensions of up to three feet tall and wide.

Container growing is more likely to result in smaller stature than in-ground cultivation.

Persian Shield

As it matures, you can take soft stem cuttings to multiply your investment for keeping or giving as gifts to your gardening friends.

Find Persian shield starter plants from Wekiva Foliage via Walmart in four-inch pots.

Maintenance

Persian shield is low-maintenance. If it gets leggy, pinch or snip the stems back just above a leaf node, to promote bushy, compact growth.

If a plant has scorched patches or brown tips pinch these off to redirect energy toward healthy growth.

Similarly, if a stem or leaf breaks, snip it off, as open wounds increase vulnerability to pests and pathogens.

If your plants experience a widespread pest infestation, or have old woody stems, you may want to take some unaffected soft stem tip cuttings to propagate new ones before disposing of the parent plant.

And finally, to try and winter over in Zone 8 or 9 for perennial growth, first remember to take a few cuttings during the summer to root in water, in case of failure.

When the foliage dies with the first frost, remove the wilted debris and apply a three-inch layer of mulch over the root zone.

Propagation

To propagate Persian shield you’ll need to take a soft stem tip cutting or purchase a potted plant from a nursery. Seeds are not readily available.

Here’s how to get started.

From a Soft Stem Tip Cutting

Cut a length of stem, measuring from the growing tip down about four or five inches. If blooming has occurred, wait until the last flower drops and a flush of new growth appears.

Be sure to make your cut about a quarter of an inch above a leaf node, the place where leaves originate.

Remove the bottom pair or pairs of leaves to reveal about three inches of bare, leafless stem.

Place the bare stem in a narrow clear container containing two inches of water. Change the water daily.

Once roots grow to at least an inch long, transplant the cutting to a well-draining vessel filled three-quarters of the way with potting soil or plant it out in the garden.

Bury about one inch of the rooted stem in the soil, so the crown, where the roots and stem meet, is buried. Tamp the soil down securely.

Maintain even moisture by watering when the top three to four inches of the soil feel dry. Avoid letting pots dry out completely, but don’t oversaturate the potting medium. 

Transplanting

For outdoor container gardening, choose a well-draining vessel with a depth of at least 12 inches. Fill it three-quarters full with organically-rich potting soil.

To transplant to the garden, work the ground soil to a depth of eight to 12 inches. Amend with compost as needed to provide organically-rich earth that drains well.

Unpot the plant and carefully detangle the roots if necessary.

Place the contents of the pot into the ground or container so that it sits at the same depth it was at in the pot.

Pests and Disease

Persian shield is not particularly prone to pests or disease. However, sometimes there are issues.

Common culprits include aphids, fungus gnats, and spider mites.

Aphids are sap-suckers that feed on foliage. If you catch them early, a firm spray with the hose may be all you need to dislodge and destroy the pests.

More extensive infestations may be treatable with an application of organic insecticidal neem oil.

Fungus gnats are flying insects that seem to appear as if by magic in overly wet soil, particularly in potted plants.

A few sticky traps and a reduction in watering will usually take care of the problem.

Spider mites are sapsuckers that feed on plants that are too dry.

A rinse with the hose, application of a pyrethrin-containing insecticide, and regular watering usually do the trick to remedy an infestation.

You are not likely to encounter any common plant diseases when cultivating S. dyerianus.

Versatile and Vibrant

Persian shield has exceptional foliage that may be enjoyed in numerous ways.

Let it reach full height, so its leggy clumps can sprawl recklessly across a garden bed, providing a gleaming, informal backdrop for foreground specimens.

Or pinch it back, sacrificing height, but achieving a bushy, compact profile suited to formal borders and well-behaved mixed groupings.

Do you grow Persian shield? Are you cultivating it indoors or outdoors, and in containers or in the garden? Share your experiences in the comments section below.

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