How to Grow and Care for Miscanthus (Silvergrass)

Miscanthus, also commonly called silvergrass, is a genus of perennial, woody, and clump-forming warm-season grasses that are hardy, long-lived, and low-maintenance. The arching grass mounds resemble a fountain with plumes of impressive feathery flowers, bringing graceful movement and structure to garden landscapes. Miscanthus is drought-resistant and grows best in full sun and rich, well-draining soil. It's best planted in the spring, although beware, it is invasive in some regions.

Miscanthus Care

Here are the main care requirements for growing miscanthus:

• Plant miscanthus in early spring, preferably in March or April.
• Give the plant full sun, although it can get scorched on the hottest summer days.
• Place the plant in rich, loamy, well-draining soils; it can handle varying pH levels.
• Avoid overly soggy soil; the plant handles drought well.
• Provide warmer temperatures for miscanthus; it dies back after sustained freezing temperatures.
  

Light

If you want to appreciate the beautiful, silvery plumes, a full sun position is best. They can tolerate light shade, but you might not see such an impressive flowering display.

The exceptions are miscanthus species with variegated foliage. Too much hot, direct sunlight can scorch the leaves.

Soil

Most Miscanthus species grow in various soil conditions and pH levels; they must be well-drained. While they thrive in relatively rich, loamy, and moist soils, they're often the go-to ornamental grass types for heavy soils as they cope surprisingly well in them.

Water

Miscanthus are typically drought-tolerant plants, so you won't need to water them often. Overly wet soils are a problem and can cause plants to die over the winter. Generally, those species with narrow leaves are a little more drought-tolerant.

A deep watering occasionally is best when there is an extended period without rainfall. It should just be enough to dampen the area around the rootball and not leave it soggy. 

Temperature and Humidity

Silvergrass can withstand various temperatures, but the plant produces its most impressive flowering display during hot summers. Excessively cold soil temperatures can damage the plant's rhizomes, a particular problem while establishing.

How much cold your miscanthus can handle depends on the species and cultivar you select. Studies indicate temperatures below 26 degrees Fahrenheit kill the hybrid species Miscanthus × giganteus (giant miscanthus), a common cultivar.

Fertilizer

A significant advantage of miscanthus is that it rarely needs additional feeding, especially when mature. The extensive rhizomes store enough nutrients to see it through the growing season. In the first couple of years, while the grass is establishing, applying a spring layer of compost made from organic matter should be sufficient.

Types of Miscanthus

There are around 20 different Miscanthus species, but the most popular to be grown ornamentally is Chinese silvergrass (M. sinensis), which also goes by other names, like maiden grass and eulalia. Miscanthus cultivars vary significantly in height and spread; dwarf varieties grow 2 feet, while larger types can grow up to 12 feet tall.

Common characteristics among various miscanthus types include:

• Seed heads: The seed heads offer visual interest before the foliage turns into shades of brown in the fall and then dies back in the winter.
• Leaves: The foliage is lush green or sometimes has an attractive variegated pattern.
• Flowers: The flowers are often a shade of purple-pink or silver, giving it its "silvergrass" name.

Here are a few popular miscanthus types:

• Zebra grass (Miscanthus sinensis 'Zebrinus'): It's known for its stunning variegated foliage, height, and attractive plumes, and it doesn't self-seed readily.
• Miscanthus sinensis 'Bandwith': This infertile cultivar is a compact variegated variety with attractive green and gold bands on the foliage.
• Porcupine grass (Miscanthus sinensis 'Strictus'): If you're looking for a tall, variegated ornamental grass to use as a focal point in your garden or at the back of your perennial border, this could be a good choice. It reaches up to 8 feet in height and has an upright growth habit; it doesn't self-seed readily.
• Maiden grass (Miscanthus sinensis 'Gracillimus'): Clumping fine-textured, silver-green blades will turn golden-bronze after the first frost and grow 4 to 6 feet; it will self-seed.
• Variegated Japanese silver grass (Miscanthus sinensis 'Variegatus'): This plant has vertical white stripes along the edges and an arching form.
• Miscanthus x giganteus: This sterile hybrid can reach up to 12 feet in one growing season. 
  

Pruning

Miscanthus doesn't need staking. To tidy up clumps and promote healthy new growth, cut back any dead leaves. Prune in late winter or, even better, early spring when new development starts appearing at the base of the clumps. To prevent invasive plant growth, remove the seedheads in the early fall.

Propagating Miscanthus

Miscanthus grows via a spreading, rhizomatous root system. A standard method of propagation is to divide the rhizomes. It's best to wait until the plants are fully established (at least two to three years old) and do it during the dormant period, ideally in the early spring.

Here's how to divide:

1. Using a shovel, dig several inches around the plant's crown to capture the edges of the root zone. Dig under the root mass and pull it all out.
   
2. Be aware that old growth can be tricky to divide, and you might need to use two forks to divide it through the crown, a root saw, or a chainsaw for large root balls.
3. Divide the clump into a 6-inch section, keeping the roots and crown intact. Keep the roots moist and plant the sections immediately.
   
4. For easier work, get assistance from someone to help lift and divide the clumps.

How to Grow Miscanthus From Seed

Miscanthus can also be grown from seed. Germination is relatively fast, usually occurring within two weeks. Miscanthus can handle cool temperatures for germination (as low as 50 degrees Fahrenheit). Germination rates reduce once temperatures rise warmer than 75 degrees Fahrenheit. If you're opting to sow them directly into the ground in early spring, only do this in regions where the soil is cool but not frosty. If sowing indoors, you can transplant seedlings once there is a minimum of at least two sets of leaves.

Here's how to sow seeds:

1. Outdoors: Sow the seeds on the soil surface about 2 to 3 feet apart for small species. Larger miscanthus varieties should be planted singularly.
2. Indoors: Start the seeds using a seed-starting potting mix in small 2.5-inch pots or flats. Press the seeds into the soil, but don't cover them. Keep the plant trays moist and warm; germination will occur in one to three weeks.
3. Transplant: Move seedlings into slightly larger 4-inch pots. Use grow lights to encourage root growth until the last frost, when they can be transplanted outside, positioned 2 to 3 feet apart.

Potting and Repotting Miscanthus

Miscanthus can grow in pots but will appreciate moist, well-drained soil. The soil of plants in pots tends to dry out and heat up faster (especially in darker pots) in full sun. But, also be mindful because constantly soggy soil can and often will cause root rot or other harmful or deadly plant diseases. To prevent too much moisture, use a pot with ample drainage holes, terra-cotta pots, and high-quality, faster-draining soil.

If transplanting from a growing tray or as a seedling, choose a large container to allow for two to three years of growth before shifting to a larger container. This might mean your planting pot would be 8 inches or more in width than the root ball of your plant. It's best to transplant in the spring before peak heat begins.

Overwintering

Miscanthus is a perennial grass, returning in the spring. However, when its rhizomatous root is young in its first winter season, it is most susceptible to damage from harsh winter temperatures.

Leave the foliage on the plants through the winter to protect the crowns from the cold. Cut away old growth just before new growth emerges in spring. Cut back the plants to a few inches above the ground.

Common Pests & Plant Diseases

A big advantage of miscanthus species is that they are primarily pest-free and don't suffer from many diseases. The plant may occasionally get mealybugs, which are challenging to treat because the pests hide inside the stems. Try using horticultural oil to remove mealybugs.

A particular fungal disease, miscanthus blight, can attack the grass blades. Another fungal disease, leaf rust, is a fungus spread by spores, especially when water splashes onto the leaves. If possible, only water the grass at the base, not from overhead. Fungal diseases can be treated with systemic or spray fungicides.

How to Get Miscanthus to Bloom

Bloom Months

Miscanthus has feathery blooms that display from August through October.

What Do Miscanthus Flowers Look and Smell Like?

Miscanthus flowers are fluffy, feathery, and wispy plumes that contain hundreds of tiny flower clusters that sway in a breeze. The scentless flowers are tan to rust-colored.

How to Encourage More Blooms

Miscanthus blooms best when planted in full sun. The soil must be moist and well-drained. If you grow this plant in even the lightest shade, you will not have as many flowers. A soggy and wet winter may also affect the number of blooms your miscanthus will display.

Deadheading Miscanthus

Deadheading miscanthus flower heads after their blooms fade and become stringy reduces the plant's ability to readily self-sow and spread. The seed heads develop in the late summer and fall and last through the winter into spring.

Common Problems With Miscanthus

Miscanthus species are generally pretty hardy, grow well in various conditions, and are low-maintenance, but certain issues can crop up depending on growing conditions and care.

Disappointing Flowering

If you experience a cool summer with little sun, you might not get the abundance of flowers you hoped for. This can also be a problem if you aren't selective about where you position your miscanthus. For example, don't plant it under a shade tree.

Brown Patches on Leaves

Excessive direct sun can result in scorch or rust along the leaf edges on miscanthus. Cut out any rusty leaves you see straight away. Select a partial shade spot with filtered light to prevent this, but only for variegated varieties.

Leaf Rolling

While miscanthus is pretty drought-tolerant, an excessive period without water can result in the foliage rolling in on itself, eventually dying from the tip. Occasional deep watering during extended dry spells helps to prevent this but be careful not to water-log the root ball.